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Movement and volume of infrapatellar fat pad and knee kinematics during quasi-static knee extension at 30 and 0° flexion in young healthy individuals
THEKNE-02928; No of Pages 10 The Knee xxx (xxxx) xxx
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The Knee
Movement and volume of infrapatellar fat pad and knee kinematics during quasi-static knee extension at 30 and 0° flexion in young healthy individuals Yuriko Okita a, Hiroyuki Oba a, Ryohei Miura a, Masashi Morimoto a, Kazuyoshi Gamada b,⁎ a b
Department of Rehabilitation, Sadamatsu Hospital, Higashihonmachi537, Omura, Nagasaki, Japan Department of Rehabilitation, Hiroshima International University, 555-36, Kurosegakuenndai, Higashihiroshimashi, Hiroshima, Japan
a r t i c l e
i n f o
Article history: Received 11 June 2019 Received in revised form 12 September 2019 Accepted 22 October 2019 Available online xxxx Keywords: Infrapatellar fat pad Healthy subjects Quasi-static knee extension 3D models MRI
a b s t r a c t Introduction: The purpose of this study was to determine the changes in the shape and volume of the infrapatellar fat pad (IPFP) associated with knee flexion angle in young healthy individuals. Methods: Young, healthy individuals without a history of knee injuries participated in this cross-sectional study. Behavior of the IPFP was quantified using three-dimensional (3D) models of the IPFP, patella, patellar tendon, femur, and tibia obtained from MRI taken at 0° and 30° flexion. The outcomes were movement and volume change of the IPFP, movement of the patella and the tibia, and change of the patellar tendon angle and length. Results: The anterior surface of the IPFP significantly moved anteriorly by 5.23 mm (p = .003) between 30° and 0°. Change in the volume of the IPFP was significantly increased or decreased in eight hyperoctants defined by the tibial coordinate system. The IPFP moved from the postero-supero hyperoctants to anterior hyperoctants. Significant correlations were observed between the IPFP and mobility of the patella, patellar tendon or tibia. Conclusion: The IPFP moves antero-inferiorly during quasi-static knee extension from 30 to 0° in young healthy individuals. Comparisons of IPFP behavior between the healthy and pathological knees may help us understand the role of IPFP and problems caused by IPFP contracture in future studies. © 2019 Elsevier B.V. All rights reserved.
1. Introduction Knee osteoarthritis (OA) is a common degenerative disease causing pain while walking [1]. Annual medical expenses per knee OA patient ranged from $1750 to $2800, and the average cost for knee replacement surgery in end-stage knee OA was reportedly $20,700 [2]. The prevalence of knee OA is about 13% for elderly people over 65 years old in the United States [3]. Knee OA affects half of the population aged 85 years old, with an estimated prevalence reaching 27 million in the United States [4]. Knee OA places a heavy burden on the individual patient and on society. Risk factors for knee OA include obesity, female, and history of knee injury [5]. In addition, the infrapatellar fat pad (IPFP) can become an inflammatory mediator [6] and may be affected in the progression of knee OA [7]. The IPFP fills the space in the front of the knee surrounded by the femur, tibia, patella and patella tendon (anterior space) [8]. Inflammation of the IPFP may cause edema, proliferation, and contracture, which may restrict knee motion [8] under conditions such as Hoffa's syndrome [9] or IPFP contracture syndrome [10]. The volume of the IPFP was found to be larger in patellofemoral (PF) OA knees than in the ⁎ Corresponding author. E-mail address: [email protected]. (K. Gamada).
https://doi.org/10.1016/j.knee.2019.10.019 0968-0160/© 2019 Elsevier B.V. All rights reserved.
Please cite this article as: Y. Okita, H. Oba, R. Miura, et al., Movement and volume of infrapatellar fat pad and knee kinematics during quasi-static knee extension ..., The Knee, https://doi.org/10.1016/j.knee.2019.10.019
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healthy knees, which correlated with pain around the PF joint [7]. The maximum area of IPFP showed a significant association with knee pain, cartilage defect, cartilage volume, OA progression, and IPFP's proliferation due to inflammation may be related to symptoms of knee OA [7]. Since the shape and volume of the space containing the IPFP may change during knee motion, stiffness and increased volume of the IPFP may reduce its ability to adapt to changes in the anterior space. Despite the body of knowledge regarding the IPFP in OA knees, knowledge of normal IPFP dynamics is lacking. Thus, differences in IPFP dynamics between OA and healthy knees remain unclear. Before performing the compassion between the two populations, a methodology of measuring the volume and shape of the IPFP should be established and the behavior of the IPFP during the quasi-static knee extension in healthy individuals should be understood. Therefore, the purpose of this study was to determine changes in the shape and volume of the IPFP associated with knee flexion angle in young, healthy individuals. Accurate measurement of the IPFP dynamics requires analyses of accurate three-dimensional (3D) morphology of the IPFP in different knee positions. However, there are no studies that have analyzed the true 3D morphology of the IPFP [7,11,12]. One previous study reported the cross-sectional area of the IPFP measured on a single MRI slice, while another study estimated IPFP volume using the cross-sectional area of IPFP. Therefore, these previous studies did not measure the true 3D IPFP volume. Since IPFP contracture syndrome may cause flexion contracture of the knee [10], it would be of interest to determine how the IPFP behaves during terminal knee extension. Terminal knee extension involves superior translation of the patella and anterior translation and extension of the tibia relative to the femur and increased angle of the patellar tendon relative to the tibia [13,14]. Therefore, it has been assumed that the IPFP migrates supero-anteriorly during terminal knee extension. The primary hypothesis of this study was that the shape of IPFP at two knee positions (0 and 30°) changes in young healthy knees. The secondary hypothesis was that the dynamics of the IPFP in these two knee positions would be related to patellar mobility, surface length of the patella tendon, patellar tendon angle, and tibial mobility. This study was designed as a cross-sectional study of healthy subjects. 2. Materials and methods 2.1. Subjects The protocol of this study was approved by the ethics committee of Sadamatsu Hospital. We recruited subjects from the staff in our institution. Inclusion criteria were asymptomatic individuals between 20 and 25 years old. Exclusion criteria were limitation of knee motion, history of surgery or fracture in the lower extremities, difficulty in understanding the research protocol, pregnant women, having communication disorder or medical risks. Limitation of knee motion was identified by a knee range below the “normal” range defined by the Japanese Orthopedic Association and The Japanese Association of Rehabilitation Medicine. Nine subjects (six males and three females, mean age 22 ± 2, height 164.3 ± 7.8, mass 58.4 ± 10.6) agreed to participate in this study after understanding the protocol, risks and benefits in this study.
0 degree
30 degrees
Figure 1. MRI and segmentation. Sagittal MRI was taken at 0 and 30° flexion in the supine position. 3D models using 3D-Doctor software (Able Software) were created. Blue indicates the IPFP, gray the tibia, green the patella, pink the patellar tendon, and orange the femur. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Please cite this article as: Y. Okita, H. Oba, R. Miura, et al., Movement and volume of infrapatellar fat pad and knee kinematics during quasi-static knee extension ..., The Knee, https://doi.org/10.1016/j.knee.2019.10.019
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2.2. Methods 2.2.1. Outcomes This study was a cross-sectional study. Behavior of the IPFP was quantified using 3D models of the patella, patellar tendon, femur, tibia and IPFP from MRI taken at 0 and 30° knee flexion. The outcomes were (1) movement of the IPFP, (2) volume change of the IPFP, (3) mobility of the patella, (4) change in the surface length of the patellar tendon, (5) change in the patellar tendon angle relative to the tibia, and (6) mobility of the tibia, obtained by positional and volume changes of each model at 30° and 0°. 2.2.2. MRI and segmentation (Figure 1) MRI of the knee was taken using 0.3T APERTO (Hitachi Medical Corporation) at 0° and 30° knee flexion while the subjects were in a supine position. The knee was considered 0° when the heel was lifted from the scanner bed so that the knees were fully extended under the gravity. The imaging sequence was 3DT1 sagittal images with a slice pitch of one millimeter spanning 250 mm across the knee (TR:3700 TE:90). The 3D models of each anatomical body were created using 3D-Doctor software (Able Software). The shape of the IPFP was compared between two independent investigators using the best-fit algorism of Geomagic software (Geomagic Corp.) and the measurement error evaluated by the surface difference was within 1.0 mm. 2.2.3. Coordinate systems embedding (Figure 2) The 3D coordinate systems were embedded onto the femur, tibia and patella using commercial 3D-Aligner software (GLAB Corp.). The X axis was directed anteriorly, Y superiorly and Z to the right for each bone. This method had high reproducibility as shown by Ikuta et al. [15]. Analyses were carried out using a total of five 3D models including the femur, tibia, patella, IPFP and patellar tendon. The coordinate systems for the femur and tibia proposed by Yamaguchi et al. [16] were utilized. The coordinate system of the patella was defined by the average point of the four tangents (superior, inferior, medial and lateral) of the patella on the coronal plane. 2.2.4. Movement of the IPFP (Figure 3) Geomagic software was used for the following analyses. The IPFP is not a rigid body whose movement can be measured using a coordinate system. Instead, we investigated the antero-posterior position of the anterior surface of the IPFP by averaging nine points on the anterior surface. We defined a three by three grid with five millimeter separations on the tibial YZ plane, which yielded nine crossing points. These crossing points were projected on the anterior surface of the IPFP without changing the Y and Z coordinates. The coordinates of these nine projected crossing points were averaged to obtain the averaged coordinate representing the antero-posterior position of the IPFP (IPFP position). Then, the anterior movement of the IPFP was defined by the IPFP position at 0° subtracted from the IPFP position at 30°. 2.2.5. Volume change of the IPFP (Figure 4) The IPFP model was divided into eight portions by three planes, specifically the tibial XY plane (or sagittal plane), tibial ZY plane (or horizontal plane) and a coronal plane parallel to the tibial YZ plane through the most anterior surface of the tibial tubercle. Then, the divided IPFP models in each hyperoctant at 0° were subtracted from the divided IPFP models at 30° to determine
Figure 2. Tibial coordinate system. Local coordinate system for the tibia was embedded using commercial 3D-Aligner software (GLAB Corp.). A rectangle was fitted onto the tibial plateau plane in which the tangent of the posterior condyles was defined to be parallel to the Z axis. The X axis was directed anteriorly, Y superiorly and Z to the right.
Please cite this article as: Y. Okita, H. Oba, R. Miura, et al., Movement and volume of infrapatellar fat pad and knee kinematics during quasi-static knee extension ..., The Knee, https://doi.org/10.1016/j.knee.2019.10.019
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Y X
Figure 3. Definition of the nine points at the anterior surface of the infrapatellar fat pad (IPFP). Using the tibial coordinate system, three by three grid with five millimeter separations on the tibial YZ plane was defined and nine crossing points were projected onto the anterior surface of the IPFP. The coordinates of the projected nine crossing points were averaged to obtain the averaged coordinate representing the antero-posterior position of the IPFP (or IPFP position).
the volume changes in each hyperoctant. We assume that the IPFP moved antero-distal-medially if the volume in the anterodistal-medial hyperoctant was increased and the volume in the postero-proximal-lateral hyperoctant was reduced.
2.2.6. Mobility of the Patella (Figure 5) The position and orientation of the patella was defined by the tibial coordinate system. The six degrees-of-freedom positions and orientations of the patella at 0° were subtracted from the positions and orientations of the patella at 30° to determine the mobility of the patella.
Figure 4. Definition of eight hyperoctants using the tibial coordinate system. a. The IPFP model was divided into eight hyperoctants by three planes, specifically tibial XY plane (or sagittal plane), tibial ZX plane (or horizontal plane) and a coronal plane parallel to the tibial YZ plane through the most anterior surface of the tibial tubercle. b. The four hyperoctants on the medial IPFP shown in the sagittal section. c. The four hyperoctants on the lateral IPFP show in the sagittal section.
Please cite this article as: Y. Okita, H. Oba, R. Miura, et al., Movement and volume of infrapatellar fat pad and knee kinematics during quasi-static knee extension ..., The Knee, https://doi.org/10.1016/j.knee.2019.10.019
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Figure 5. Patellar movement during a quasi-static knee extension from 30 (gray) to 0° (green). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
2.2.7. Surface length of the patellar tendon (Figure 6) Using Geomagic, the surface length of the patellar tendon was computed by defining the most proximal and most distal points at the anterior surface of the patellar tendon, then computing the surface length. The surface length at 0° was subtracted from the surface length at 30° to determine the change in the surface length of the patellar tendon. 2.2.8. Patellar tendon angle (Figure 7) The patellar tendon angle for the tibia was calculated using Geomagic and ImageJ. The tibia and patellar tendon models were oriented so that the XY plane is shown on the Geomagic screen. Then, the screenshot of the image was imported to the ImageJ
Figure 6. Definition of length, surface length of the patella tendon. The length of the patella tendon is defined by the straight distance between the attachments. The surface length of the patellar tendon was defined as the total length of the surface of the center of the patellar tendon. Pink represents the patellar tendon at 0°, gray at 30°, white the straight distance between the attachments, and yellow the surface of the patellar tendon. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Please cite this article as: Y. Okita, H. Oba, R. Miura, et al., Movement and volume of infrapatellar fat pad and knee kinematics during quasi-static knee extension ..., The Knee, https://doi.org/10.1016/j.knee.2019.10.019
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Figure 7. Definition of the patellar tendon angle. The cross section image at the XY plane was imported into the ImageJ program. Measured was the angle between the tibial Y axis (yellow) and the orientation of the patellar tendon (blue) defined by connecting the most proximal and most distal points at the anterior surface of the patella tendon. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
program in order to measure the angle between the tibial Y axis and the orientation of the patellar tendon defined by connecting the most proximal and most distal points at the anterior surface of the patella tendon. The patellar tendon angle at 0° was subtracted from the patellar tendon angle at 30° to determine the change in the patellar tendon angle between the two knee positions. 2.2.9. Mobility of the tibia The coordinate of the origin of the tibia in the femoral coordinate system was defined as the position of the tibia. The six degrees-of-freedom positions and orientations of the tibia at 0° was subtracted from the positions and orientations of the tibia at 30° to determine the mobility of the tibia relative to the femur. 2.2.10. Statistics We determined the 95% confidence interval (CI) for each parameter. Paired T-test was used to compare each parameter between 0° and 30°. Pearson's correlation coefficient or Spearman's correlation coefficient was used to determine the association between the movement or volume change of the IPFP and other parameters. The significance level was set at alpha = 0.05. SPSS Ver.14 was used for statistical analysis. 3. Results The absolute values and p values of each parameter are summarized in Table 1. The anterior surface of the IPFP moved anteriorly by 5.23 mm (95% CI [−4.69, −1.11])(p = .003) from 30° to 0° (Figure 8). For the IPFP volume, significant increase in volume from 30° to 0° was observed in the antero-infero-medial hyperoctant by 1558.76 mm3 (95% CI [690.84, 2426.69])(p b .012),
Table 1 Demographic data for all subjects. Subjects (mean ± SD) Male (n) Female (n) Age (years) Height (m) Mass (kg) BMI (kg/m2)
5 3 22 ± 2 164.3 ± 7.8 58.4 ± 10.6 21.5 ± 2.5
BMI: Body Mass Index.
Please cite this article as: Y. Okita, H. Oba, R. Miura, et al., Movement and volume of infrapatellar fat pad and knee kinematics during quasi-static knee extension ..., The Knee, https://doi.org/10.1016/j.knee.2019.10.019
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Figure 8. The anterior movement of the infrapatellar fat pad (IPFP) during the quasi-static knee extension from 30 to 0°. The anterior surface of the IPFP moved anteriorly by 5.23 (95% CI [−4.69, −1.11]) mm (p = .003) from 30 to 0°. Green represents the IPFP at 0°and gray at 30°. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
the postero-infero-medial hyperoctant by 197.76 mm3 (95% CI [− 121.97, 517.49])(p = .187), the antero-infero-lateral hyperoctant by 1147.19 mm3 (95% CI [304.00, 1990.37])(p b .015), the postero-infero-lateral hyperoctant by 367.55 mm3 (95% CI [− 145.78, 880.87])(p = .134), and the antero-supero-medial hyperoctant by 1993.46 mm3 (95% CI [1356.05, 2630.05]) (p b .000). On the other hand, significant decrease in volume from 30° to 0° was observed in the postero-supero-medial hyperoctant by − 1323.91 mm3 (95% CI [− 3237.44, 589.62])(p = .146), the antero-supero-lateral hyperoctant by −1027.32 mm3 (95% CI [−2261.29, 206.65]) (p = .09), and the postero-supero-lateral hyperoctant by −3642.44 mm3 (95% CI [−4643.74, −2641.14])(p b .000). There were significant increases in three of four anterior hyperoctants. A significant decrease from 30° to 0° was observed in the postero-supero-lateral hyperoctant. Based on these findings, the IPFP moved from the posterosupero hyperoctants to the anterior hyperoctants with the change from 30° to 0° flexion (Figure 9). Other outcomes included the patellar tendon angle, surface length of the patellar tendon, and patella movement (Table 2). The patellar tendon angle was significantly increased from 30° to 0° by 3.67° (95% CI [0.75, 6.59])(p b .018). The surface length of the patellar tendon was significantly decreased from 30° to 0° by 4.37 mm (95% CI [−7.74, −1.00])(p b .015). The patella moved anteriorly by 2.71 mm and superiorly by 15.26 mm, and showed medial translation of 1.10 mm with the change from 30° to 0° flexion. Correlation coefficients were observed between the variables. There were significant correlations between the movement or volume change of the IPFP and the other parameters (Table 3). First, there was a significant correlation between the anterior
Decrease
a
b
Figure 9. Representation of increase or decrease of the volume of the eight hyperoctants. a. All cuboids represent the baseline volume of the eight hyperoctants at 30°. b. Each cuboid represents the relative volume of the eight hyperoctants at 0°relative to the volume at 30°. Pink cuboids represent significant increase, blue shows significant decrease, and gray had no statistically significant difference. The IPFP moved from the postero-supero hyperoctants to the anterior hyperoctants from 30 to 0°. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
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Table 2 Comparisons of patellar tendon angle, six degrees-of-freedom position and orientation of the patella and tibia. Subjects
Patellar tendon
Patella displacement from 30 to 0° relative to the tibial local coordinate system Tibial rotation
Width (mm) Length (mm) Angle (°) Surface length (mm) Anterior translation (mm) Superior translation (mm) Lateral translation(mm) Abduction (°) External rotation (°) Extension (°) External rotation (°) Abduction (°) Lateral translation (mm)
Intragroup difference
0°
30°
⊿
p-Value
22.0 ± 6.6 68.1 ± 6.6 35.5 ± 5.8 49.9 ± 4.8 – – – – – – 3.9 ± 5.3 1.0 ± 1.3 2.1 ± 2.2
22.9 ± 7.0 76.3 ± 11.0 30.4 ± 5.6 53.4 ± 6.9 – – – – – – −2.9 ± 4.8 −1.8 ± 1.4 −0.6 ± 1.2
−0.9 −8.2 5.1 −3.5 2.7 15.3 −1.1 0.0 0.0 4.0 6.8 2.7 2.7
– – – – – – – – – – – – –
movement of the IPFP and patellar lateral translation (r = 0.747, p = .033). Second, tibial external rotation correlated with: (1) the IPFP volume change in the postero-supero-medial hyperoctant from 30° to 0° (r = − 0.805, p = .029), IPFP volume change in the antero-infero-medial hyperoctant (r = 0.849 p = .016) and IPFP volume change in the antero-infero-lateral hyperoctant (r = 0.786 p = .036). Tibial lateral translation correlated with the IPFP volume change in the antero-superomedial hyperoctant from 30° to 0° (r = 0.791, p = .034). Accordingly, IPFP volume change was associated with tibial and patellar movement with the change from 30° to 0° flexion.creased after patellar tendinopathy or patients with 4. Discussion The purpose of this study was to determine changes in the shape and volume of the IPFP associated with knee flexion angle in young, healthy individuals using 3D models. We hypothesized that: (1) the shape of the IPFP at two knee positions (0 and 30°) changes in the young healthy knee; and (2) the dynamics of the IPFP at these two knee positions is related to patellar mobility, surface length of the patellar tendon, patellar tendon angle, and tibial mobility. The IPFP moved significantly anteriorly from 30° to 0° knee flexion, which was confirmed by an increase in the patellar tendon angle. Significant correlations were found between various parameters of IPFP movement and IPFP volume change, as well as mobility of the tibia and patella. More specifically, antero-inferior movement of the IPFP was associated with tibial external rotation and patellar lateral translation. This study, to our knowledge, is the first study to measure the 3D movement of the IPFP during quasi-static or dynamic knee extension, and there are no previous studies to compare our data with. Regarding the IPFP volume, the antero-inferior hyperoctants and the antero-supero-medial hyperoctant significantly increased from 30° to 0°, while the postero-superior hyperoctants were significantly decreased. Based on these findings regarding IPFP volume in each of the eight hyperoctants, the IPFP showed the possibility of migrating from postero-superior to anterior from 30° to 0° of knee flexion. This speculation was supported by the greater patellar tendon angle at 0° and shorter length of the patellar tendon suggesting that the patellar tendon was pressed from behind by the IPFP at 0°. Anterior movement of the IPFP may be caused by protrusion of the anterior contour of the femoral condyles in extension as compared with that in flexion. The amount of the IPFP has been shown to be increased after patellar tendinopathy or patients with PF OA [7,17]. In a cadaveric study, the IPFP expanded medially and laterally with knee flexion, and there was adhesion between the IPFP and the tibia, patellar tendon, lateral meniscus, or medial meniscus via the ligament [18]. Therefore, movement of the IPFP may be reduced by knee pathology and/or aging, which may reduce the mobility of the knee. We have limited knowledge of the effect of IPFP stiffness, which will need to be determined in future studies. Table 3 Comparison of excursion of the anterior surface and volume of divided portions of the infrapatellar fat pad. Subjects
Anterior motion of the anterior surface of the IPFP (mm) Antero-supero-medial Divided portions of IPFP Postero-supero medial (mm3) Anterp-supero-latelal Postero-supero-latelal Antero-infero-medial Postero-infero-medial Antero-infero-lateral Postero-infero-lateral
Intragroup difference
0°
30°
44.5 ± 4.4
38.7 ± 3.1
8175.9 ± 2538.4 2021.5 ± 1106.2 6877.2 ± 2267.9 3283.8 ± 1981.8 2161.5 ± 1187.7 910.1 ± 1004.3 2797.8 ± 1126.5 2335.0 ± 1153.1
6182.4 ± 2449.6 3345.4 ± 3011.8 7904.5 ± 2675.4 6926.2 ± 2462.7 602.7 ± 213.3 712.3 ± 1210.2 1650.6 ± 915.8 1967.4 ± 652.6
⊿
p-Value 5.8
1993.5 −1323.9 −1027.3 −3642.4 1558.8 197.8 1147.2 367.6
b.000 .146 .090 b.000 .004 .187 .015 .134
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Antero-inferior movement of the IPFP was associated with tibial external rotation and patellar lateral translation. This suggests that tibial external rotation induces anterior pressure from the femoral condyle onto the IPFP, causing greater anterior movement. In addition, patellar lateral translation should create space in the medial facet of the PF joint, which might induce IPFP movement into the space in the medial PF joint, causing antero-superior migration of the IPFP. Paulos et al. suggested criteria of IPFP contracture such that Stage 1 involves indurated synovial, fat pad and retinacular tissues, with a painful range of motion, restricted patellar mobility, and quadriceps lag, Stage 2 involves presence of the “shelf sign”, continued peripatellar swelling, and induration with severely restricted patellar tendon, restricted super glide of the patella, and Stage 3 involves developmental patella infera [10]. In a paper reporting the results of surgical release in 28 consecutive cases of IPFP contracture syndrome (IPCS) with a follow-up period of three months to four years, there were 12° increases in extension and 35° increases in the flexion range of motion, followed by PF arthrosis in 80% and patella infera in 16%. Ellen et al. reported a patient with IPFP contracture, who presented with worsening pain and rehabilitation delay [19]. Therefore, it can easily be assumed that IPFP contracture syndrome is induced by inflammation of the IPFP and that stiffness and enlargement of the IPFP reduce patellar mobility and limit quadriceps strength. The current study showed the mobility of the IPFP during quasi-static knee extension, and it would be interesting to compare these findings with the findings in pathological knees with OA or after arthroscopy. We are unaware of the exact causes of the IPFP stiffness or adhesion, some of the factors may include aging, fibrosis after inflammation by injury or repetitive mechanical stress such as repetitive kneeling, KOA with continuous inflammation in the knee joint, trauma, and surgery. Synovial fibrosis of IPFP would occur if IPFP would be with inflammation [20]. Murakami et al.[20] reported increased fibrosis in patients who had pain on exertion or stiffness in squatting after the reconstructive surgery. Adhesion may limit its ability to change its shape during knee movements which induce further mechanical stress on the IPFP. We utilized 3D models of the bones and IPFP obtained by manual segmentation of MRI with a slice pitch of one millimeter. We examined healthy young people without knee pain or history of surgery. Therefore, we consider that these results can be generalized to similar populations without knee pain or history of surgery on the knee. The limitation of this research included the small sample size, which may have introduced beta errors in the results. Since the subjects of this study were young healthy individuals, we should generalize these results to healthy young people only. Segmentation of the IPFP using MRI is sometimes difficult to determine especially at the periphery due to the low contrast between fat and other tissues. The joint positions of 30° and 0° were determined using a goniometer, which may also have introduced some errors. However, despite the above limitations, there is no apparent source of significant bias that would prevent the statement of a firm conclusion. To conclude, the IPFP in the healthy knees moves antero-inferiorly during knee extension. Antero-inferior movement of the IPFP is associated with tibial external rotation and patellar lateral translation. Comparisons of IPFP behavior between healthy and pathological knees in future studies may clarify the role of the IPFP and elucidate problems caused by IPFP contracture. 5. Conclusion In the healthy knee, the IPFP moves antero-inferiorly during knee extension. Antero-inferior movement of the IPFP is associated with tibial external rotation and patellar lateral translation. Comparisons of IPFP behavior between healthy and pathological knees in future studies may clarify the role of the IPFP and elucidate problems caused by IPFP contracture. Contribution Yuriko Okita was involved in data analysis and manuscript writing. Hiroyuki Oba recruited subjects and was involved in data management and analysis. Ryohei Miura recruited subjects and was involved in analysis and manuscript writing. Masashi Morimoto recruited subjects and was involved in data acquisition and analysis. Kazuyoshi Gamada was involved in planning, analysis and manuscript writing. Declaration of competing interest Kazuyoshi Gamada is CEO of GLAB Corp. Inc., which had no influence on this study. No other authors have any conflicting interests to disclose. Acknowledgement The authors received no funding for this study. References [1] Bosomworth NJ. Exercise and knee osteoarthritis: benefit or hazard? Can Fam Physician Sep 2009;55(9):871–8. [2] Gupta S, Hawker GA, Laporte A, Croxford R, Coyte PC. The economic burden of disabling hip and knee osteoarthritis (OA) from the perspective of individuals living with this condition. Rheumatology (Oxford) Dec 2005;44(12):1531–7. [3] Lawrence RC, Helmick CG, Arnett FC, Deyo RA, Felson DT, Giannini EH, et al. Estimates of the prevalence of arthritis and selected musculoskeletal disorders in the United States. Arthritis Rheum May 1998;41(5):778–99. [4] Felson DT. An update on the pathogenesis and epidemiology of osteoarthritis. Radiol Clin North Am Jan 2004;42(1):1–9 [v].
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The Knee
Movement and volume of infrapatellar fat pad and knee kinematics during quasi-static knee extension at 30 and 0° flexion in young healthy individuals Yuriko Okita a, Hiroyuki Oba a, Ryohei Miura a, Masashi Morimoto a, Kazuyoshi Gamada b,⁎ a b
Department of Rehabilitation, Sadamatsu Hospital, Higashihonmachi537, Omura, Nagasaki, Japan Department of Rehabilitation, Hiroshima International University, 555-36, Kurosegakuenndai, Higashihiroshimashi, Hiroshima, Japan
a r t i c l e
i n f o
Article history: Received 11 June 2019 Received in revised form 12 September 2019 Accepted 22 October 2019 Available online xxxx Keywords: Infrapatellar fat pad Healthy subjects Quasi-static knee extension 3D models MRI
a b s t r a c t Introduction: The purpose of this study was to determine the changes in the shape and volume of the infrapatellar fat pad (IPFP) associated with knee flexion angle in young healthy individuals. Methods: Young, healthy individuals without a history of knee injuries participated in this cross-sectional study. Behavior of the IPFP was quantified using three-dimensional (3D) models of the IPFP, patella, patellar tendon, femur, and tibia obtained from MRI taken at 0° and 30° flexion. The outcomes were movement and volume change of the IPFP, movement of the patella and the tibia, and change of the patellar tendon angle and length. Results: The anterior surface of the IPFP significantly moved anteriorly by 5.23 mm (p = .003) between 30° and 0°. Change in the volume of the IPFP was significantly increased or decreased in eight hyperoctants defined by the tibial coordinate system. The IPFP moved from the postero-supero hyperoctants to anterior hyperoctants. Significant correlations were observed between the IPFP and mobility of the patella, patellar tendon or tibia. Conclusion: The IPFP moves antero-inferiorly during quasi-static knee extension from 30 to 0° in young healthy individuals. Comparisons of IPFP behavior between the healthy and pathological knees may help us understand the role of IPFP and problems caused by IPFP contracture in future studies. © 2019 Elsevier B.V. All rights reserved.
1. Introduction Knee osteoarthritis (OA) is a common degenerative disease causing pain while walking [1]. Annual medical expenses per knee OA patient ranged from $1750 to $2800, and the average cost for knee replacement surgery in end-stage knee OA was reportedly $20,700 [2]. The prevalence of knee OA is about 13% for elderly people over 65 years old in the United States [3]. Knee OA affects half of the population aged 85 years old, with an estimated prevalence reaching 27 million in the United States [4]. Knee OA places a heavy burden on the individual patient and on society. Risk factors for knee OA include obesity, female, and history of knee injury [5]. In addition, the infrapatellar fat pad (IPFP) can become an inflammatory mediator [6] and may be affected in the progression of knee OA [7]. The IPFP fills the space in the front of the knee surrounded by the femur, tibia, patella and patella tendon (anterior space) [8]. Inflammation of the IPFP may cause edema, proliferation, and contracture, which may restrict knee motion [8] under conditions such as Hoffa's syndrome [9] or IPFP contracture syndrome [10]. The volume of the IPFP was found to be larger in patellofemoral (PF) OA knees than in the ⁎ Corresponding author. E-mail address: [email protected]. (K. Gamada).
https://doi.org/10.1016/j.knee.2019.10.019 0968-0160/© 2019 Elsevier B.V. All rights reserved.
Please cite this article as: Y. Okita, H. Oba, R. Miura, et al., Movement and volume of infrapatellar fat pad and knee kinematics during quasi-static knee extension ..., The Knee, https://doi.org/10.1016/j.knee.2019.10.019
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healthy knees, which correlated with pain around the PF joint [7]. The maximum area of IPFP showed a significant association with knee pain, cartilage defect, cartilage volume, OA progression, and IPFP's proliferation due to inflammation may be related to symptoms of knee OA [7]. Since the shape and volume of the space containing the IPFP may change during knee motion, stiffness and increased volume of the IPFP may reduce its ability to adapt to changes in the anterior space. Despite the body of knowledge regarding the IPFP in OA knees, knowledge of normal IPFP dynamics is lacking. Thus, differences in IPFP dynamics between OA and healthy knees remain unclear. Before performing the compassion between the two populations, a methodology of measuring the volume and shape of the IPFP should be established and the behavior of the IPFP during the quasi-static knee extension in healthy individuals should be understood. Therefore, the purpose of this study was to determine changes in the shape and volume of the IPFP associated with knee flexion angle in young, healthy individuals. Accurate measurement of the IPFP dynamics requires analyses of accurate three-dimensional (3D) morphology of the IPFP in different knee positions. However, there are no studies that have analyzed the true 3D morphology of the IPFP [7,11,12]. One previous study reported the cross-sectional area of the IPFP measured on a single MRI slice, while another study estimated IPFP volume using the cross-sectional area of IPFP. Therefore, these previous studies did not measure the true 3D IPFP volume. Since IPFP contracture syndrome may cause flexion contracture of the knee [10], it would be of interest to determine how the IPFP behaves during terminal knee extension. Terminal knee extension involves superior translation of the patella and anterior translation and extension of the tibia relative to the femur and increased angle of the patellar tendon relative to the tibia [13,14]. Therefore, it has been assumed that the IPFP migrates supero-anteriorly during terminal knee extension. The primary hypothesis of this study was that the shape of IPFP at two knee positions (0 and 30°) changes in young healthy knees. The secondary hypothesis was that the dynamics of the IPFP in these two knee positions would be related to patellar mobility, surface length of the patella tendon, patellar tendon angle, and tibial mobility. This study was designed as a cross-sectional study of healthy subjects. 2. Materials and methods 2.1. Subjects The protocol of this study was approved by the ethics committee of Sadamatsu Hospital. We recruited subjects from the staff in our institution. Inclusion criteria were asymptomatic individuals between 20 and 25 years old. Exclusion criteria were limitation of knee motion, history of surgery or fracture in the lower extremities, difficulty in understanding the research protocol, pregnant women, having communication disorder or medical risks. Limitation of knee motion was identified by a knee range below the “normal” range defined by the Japanese Orthopedic Association and The Japanese Association of Rehabilitation Medicine. Nine subjects (six males and three females, mean age 22 ± 2, height 164.3 ± 7.8, mass 58.4 ± 10.6) agreed to participate in this study after understanding the protocol, risks and benefits in this study.
0 degree
30 degrees
Figure 1. MRI and segmentation. Sagittal MRI was taken at 0 and 30° flexion in the supine position. 3D models using 3D-Doctor software (Able Software) were created. Blue indicates the IPFP, gray the tibia, green the patella, pink the patellar tendon, and orange the femur. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
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2.2. Methods 2.2.1. Outcomes This study was a cross-sectional study. Behavior of the IPFP was quantified using 3D models of the patella, patellar tendon, femur, tibia and IPFP from MRI taken at 0 and 30° knee flexion. The outcomes were (1) movement of the IPFP, (2) volume change of the IPFP, (3) mobility of the patella, (4) change in the surface length of the patellar tendon, (5) change in the patellar tendon angle relative to the tibia, and (6) mobility of the tibia, obtained by positional and volume changes of each model at 30° and 0°. 2.2.2. MRI and segmentation (Figure 1) MRI of the knee was taken using 0.3T APERTO (Hitachi Medical Corporation) at 0° and 30° knee flexion while the subjects were in a supine position. The knee was considered 0° when the heel was lifted from the scanner bed so that the knees were fully extended under the gravity. The imaging sequence was 3DT1 sagittal images with a slice pitch of one millimeter spanning 250 mm across the knee (TR:3700 TE:90). The 3D models of each anatomical body were created using 3D-Doctor software (Able Software). The shape of the IPFP was compared between two independent investigators using the best-fit algorism of Geomagic software (Geomagic Corp.) and the measurement error evaluated by the surface difference was within 1.0 mm. 2.2.3. Coordinate systems embedding (Figure 2) The 3D coordinate systems were embedded onto the femur, tibia and patella using commercial 3D-Aligner software (GLAB Corp.). The X axis was directed anteriorly, Y superiorly and Z to the right for each bone. This method had high reproducibility as shown by Ikuta et al. [15]. Analyses were carried out using a total of five 3D models including the femur, tibia, patella, IPFP and patellar tendon. The coordinate systems for the femur and tibia proposed by Yamaguchi et al. [16] were utilized. The coordinate system of the patella was defined by the average point of the four tangents (superior, inferior, medial and lateral) of the patella on the coronal plane. 2.2.4. Movement of the IPFP (Figure 3) Geomagic software was used for the following analyses. The IPFP is not a rigid body whose movement can be measured using a coordinate system. Instead, we investigated the antero-posterior position of the anterior surface of the IPFP by averaging nine points on the anterior surface. We defined a three by three grid with five millimeter separations on the tibial YZ plane, which yielded nine crossing points. These crossing points were projected on the anterior surface of the IPFP without changing the Y and Z coordinates. The coordinates of these nine projected crossing points were averaged to obtain the averaged coordinate representing the antero-posterior position of the IPFP (IPFP position). Then, the anterior movement of the IPFP was defined by the IPFP position at 0° subtracted from the IPFP position at 30°. 2.2.5. Volume change of the IPFP (Figure 4) The IPFP model was divided into eight portions by three planes, specifically the tibial XY plane (or sagittal plane), tibial ZY plane (or horizontal plane) and a coronal plane parallel to the tibial YZ plane through the most anterior surface of the tibial tubercle. Then, the divided IPFP models in each hyperoctant at 0° were subtracted from the divided IPFP models at 30° to determine
Figure 2. Tibial coordinate system. Local coordinate system for the tibia was embedded using commercial 3D-Aligner software (GLAB Corp.). A rectangle was fitted onto the tibial plateau plane in which the tangent of the posterior condyles was defined to be parallel to the Z axis. The X axis was directed anteriorly, Y superiorly and Z to the right.
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Y X
Figure 3. Definition of the nine points at the anterior surface of the infrapatellar fat pad (IPFP). Using the tibial coordinate system, three by three grid with five millimeter separations on the tibial YZ plane was defined and nine crossing points were projected onto the anterior surface of the IPFP. The coordinates of the projected nine crossing points were averaged to obtain the averaged coordinate representing the antero-posterior position of the IPFP (or IPFP position).
the volume changes in each hyperoctant. We assume that the IPFP moved antero-distal-medially if the volume in the anterodistal-medial hyperoctant was increased and the volume in the postero-proximal-lateral hyperoctant was reduced.
2.2.6. Mobility of the Patella (Figure 5) The position and orientation of the patella was defined by the tibial coordinate system. The six degrees-of-freedom positions and orientations of the patella at 0° were subtracted from the positions and orientations of the patella at 30° to determine the mobility of the patella.
Figure 4. Definition of eight hyperoctants using the tibial coordinate system. a. The IPFP model was divided into eight hyperoctants by three planes, specifically tibial XY plane (or sagittal plane), tibial ZX plane (or horizontal plane) and a coronal plane parallel to the tibial YZ plane through the most anterior surface of the tibial tubercle. b. The four hyperoctants on the medial IPFP shown in the sagittal section. c. The four hyperoctants on the lateral IPFP show in the sagittal section.
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Figure 5. Patellar movement during a quasi-static knee extension from 30 (gray) to 0° (green). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
2.2.7. Surface length of the patellar tendon (Figure 6) Using Geomagic, the surface length of the patellar tendon was computed by defining the most proximal and most distal points at the anterior surface of the patellar tendon, then computing the surface length. The surface length at 0° was subtracted from the surface length at 30° to determine the change in the surface length of the patellar tendon. 2.2.8. Patellar tendon angle (Figure 7) The patellar tendon angle for the tibia was calculated using Geomagic and ImageJ. The tibia and patellar tendon models were oriented so that the XY plane is shown on the Geomagic screen. Then, the screenshot of the image was imported to the ImageJ
Figure 6. Definition of length, surface length of the patella tendon. The length of the patella tendon is defined by the straight distance between the attachments. The surface length of the patellar tendon was defined as the total length of the surface of the center of the patellar tendon. Pink represents the patellar tendon at 0°, gray at 30°, white the straight distance between the attachments, and yellow the surface of the patellar tendon. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Please cite this article as: Y. Okita, H. Oba, R. Miura, et al., Movement and volume of infrapatellar fat pad and knee kinematics during quasi-static knee extension ..., The Knee, https://doi.org/10.1016/j.knee.2019.10.019
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Figure 7. Definition of the patellar tendon angle. The cross section image at the XY plane was imported into the ImageJ program. Measured was the angle between the tibial Y axis (yellow) and the orientation of the patellar tendon (blue) defined by connecting the most proximal and most distal points at the anterior surface of the patella tendon. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
program in order to measure the angle between the tibial Y axis and the orientation of the patellar tendon defined by connecting the most proximal and most distal points at the anterior surface of the patella tendon. The patellar tendon angle at 0° was subtracted from the patellar tendon angle at 30° to determine the change in the patellar tendon angle between the two knee positions. 2.2.9. Mobility of the tibia The coordinate of the origin of the tibia in the femoral coordinate system was defined as the position of the tibia. The six degrees-of-freedom positions and orientations of the tibia at 0° was subtracted from the positions and orientations of the tibia at 30° to determine the mobility of the tibia relative to the femur. 2.2.10. Statistics We determined the 95% confidence interval (CI) for each parameter. Paired T-test was used to compare each parameter between 0° and 30°. Pearson's correlation coefficient or Spearman's correlation coefficient was used to determine the association between the movement or volume change of the IPFP and other parameters. The significance level was set at alpha = 0.05. SPSS Ver.14 was used for statistical analysis. 3. Results The absolute values and p values of each parameter are summarized in Table 1. The anterior surface of the IPFP moved anteriorly by 5.23 mm (95% CI [−4.69, −1.11])(p = .003) from 30° to 0° (Figure 8). For the IPFP volume, significant increase in volume from 30° to 0° was observed in the antero-infero-medial hyperoctant by 1558.76 mm3 (95% CI [690.84, 2426.69])(p b .012),
Table 1 Demographic data for all subjects. Subjects (mean ± SD) Male (n) Female (n) Age (years) Height (m) Mass (kg) BMI (kg/m2)
5 3 22 ± 2 164.3 ± 7.8 58.4 ± 10.6 21.5 ± 2.5
BMI: Body Mass Index.
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Figure 8. The anterior movement of the infrapatellar fat pad (IPFP) during the quasi-static knee extension from 30 to 0°. The anterior surface of the IPFP moved anteriorly by 5.23 (95% CI [−4.69, −1.11]) mm (p = .003) from 30 to 0°. Green represents the IPFP at 0°and gray at 30°. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
the postero-infero-medial hyperoctant by 197.76 mm3 (95% CI [− 121.97, 517.49])(p = .187), the antero-infero-lateral hyperoctant by 1147.19 mm3 (95% CI [304.00, 1990.37])(p b .015), the postero-infero-lateral hyperoctant by 367.55 mm3 (95% CI [− 145.78, 880.87])(p = .134), and the antero-supero-medial hyperoctant by 1993.46 mm3 (95% CI [1356.05, 2630.05]) (p b .000). On the other hand, significant decrease in volume from 30° to 0° was observed in the postero-supero-medial hyperoctant by − 1323.91 mm3 (95% CI [− 3237.44, 589.62])(p = .146), the antero-supero-lateral hyperoctant by −1027.32 mm3 (95% CI [−2261.29, 206.65]) (p = .09), and the postero-supero-lateral hyperoctant by −3642.44 mm3 (95% CI [−4643.74, −2641.14])(p b .000). There were significant increases in three of four anterior hyperoctants. A significant decrease from 30° to 0° was observed in the postero-supero-lateral hyperoctant. Based on these findings, the IPFP moved from the posterosupero hyperoctants to the anterior hyperoctants with the change from 30° to 0° flexion (Figure 9). Other outcomes included the patellar tendon angle, surface length of the patellar tendon, and patella movement (Table 2). The patellar tendon angle was significantly increased from 30° to 0° by 3.67° (95% CI [0.75, 6.59])(p b .018). The surface length of the patellar tendon was significantly decreased from 30° to 0° by 4.37 mm (95% CI [−7.74, −1.00])(p b .015). The patella moved anteriorly by 2.71 mm and superiorly by 15.26 mm, and showed medial translation of 1.10 mm with the change from 30° to 0° flexion. Correlation coefficients were observed between the variables. There were significant correlations between the movement or volume change of the IPFP and the other parameters (Table 3). First, there was a significant correlation between the anterior
Decrease
a
b
Figure 9. Representation of increase or decrease of the volume of the eight hyperoctants. a. All cuboids represent the baseline volume of the eight hyperoctants at 30°. b. Each cuboid represents the relative volume of the eight hyperoctants at 0°relative to the volume at 30°. Pink cuboids represent significant increase, blue shows significant decrease, and gray had no statistically significant difference. The IPFP moved from the postero-supero hyperoctants to the anterior hyperoctants from 30 to 0°. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
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Table 2 Comparisons of patellar tendon angle, six degrees-of-freedom position and orientation of the patella and tibia. Subjects
Patellar tendon
Patella displacement from 30 to 0° relative to the tibial local coordinate system Tibial rotation
Width (mm) Length (mm) Angle (°) Surface length (mm) Anterior translation (mm) Superior translation (mm) Lateral translation(mm) Abduction (°) External rotation (°) Extension (°) External rotation (°) Abduction (°) Lateral translation (mm)
Intragroup difference
0°
30°
⊿
p-Value
22.0 ± 6.6 68.1 ± 6.6 35.5 ± 5.8 49.9 ± 4.8 – – – – – – 3.9 ± 5.3 1.0 ± 1.3 2.1 ± 2.2
22.9 ± 7.0 76.3 ± 11.0 30.4 ± 5.6 53.4 ± 6.9 – – – – – – −2.9 ± 4.8 −1.8 ± 1.4 −0.6 ± 1.2
−0.9 −8.2 5.1 −3.5 2.7 15.3 −1.1 0.0 0.0 4.0 6.8 2.7 2.7
– – – – – – – – – – – – –
movement of the IPFP and patellar lateral translation (r = 0.747, p = .033). Second, tibial external rotation correlated with: (1) the IPFP volume change in the postero-supero-medial hyperoctant from 30° to 0° (r = − 0.805, p = .029), IPFP volume change in the antero-infero-medial hyperoctant (r = 0.849 p = .016) and IPFP volume change in the antero-infero-lateral hyperoctant (r = 0.786 p = .036). Tibial lateral translation correlated with the IPFP volume change in the antero-superomedial hyperoctant from 30° to 0° (r = 0.791, p = .034). Accordingly, IPFP volume change was associated with tibial and patellar movement with the change from 30° to 0° flexion.creased after patellar tendinopathy or patients with 4. Discussion The purpose of this study was to determine changes in the shape and volume of the IPFP associated with knee flexion angle in young, healthy individuals using 3D models. We hypothesized that: (1) the shape of the IPFP at two knee positions (0 and 30°) changes in the young healthy knee; and (2) the dynamics of the IPFP at these two knee positions is related to patellar mobility, surface length of the patellar tendon, patellar tendon angle, and tibial mobility. The IPFP moved significantly anteriorly from 30° to 0° knee flexion, which was confirmed by an increase in the patellar tendon angle. Significant correlations were found between various parameters of IPFP movement and IPFP volume change, as well as mobility of the tibia and patella. More specifically, antero-inferior movement of the IPFP was associated with tibial external rotation and patellar lateral translation. This study, to our knowledge, is the first study to measure the 3D movement of the IPFP during quasi-static or dynamic knee extension, and there are no previous studies to compare our data with. Regarding the IPFP volume, the antero-inferior hyperoctants and the antero-supero-medial hyperoctant significantly increased from 30° to 0°, while the postero-superior hyperoctants were significantly decreased. Based on these findings regarding IPFP volume in each of the eight hyperoctants, the IPFP showed the possibility of migrating from postero-superior to anterior from 30° to 0° of knee flexion. This speculation was supported by the greater patellar tendon angle at 0° and shorter length of the patellar tendon suggesting that the patellar tendon was pressed from behind by the IPFP at 0°. Anterior movement of the IPFP may be caused by protrusion of the anterior contour of the femoral condyles in extension as compared with that in flexion. The amount of the IPFP has been shown to be increased after patellar tendinopathy or patients with PF OA [7,17]. In a cadaveric study, the IPFP expanded medially and laterally with knee flexion, and there was adhesion between the IPFP and the tibia, patellar tendon, lateral meniscus, or medial meniscus via the ligament [18]. Therefore, movement of the IPFP may be reduced by knee pathology and/or aging, which may reduce the mobility of the knee. We have limited knowledge of the effect of IPFP stiffness, which will need to be determined in future studies. Table 3 Comparison of excursion of the anterior surface and volume of divided portions of the infrapatellar fat pad. Subjects
Anterior motion of the anterior surface of the IPFP (mm) Antero-supero-medial Divided portions of IPFP Postero-supero medial (mm3) Anterp-supero-latelal Postero-supero-latelal Antero-infero-medial Postero-infero-medial Antero-infero-lateral Postero-infero-lateral
Intragroup difference
0°
30°
44.5 ± 4.4
38.7 ± 3.1
8175.9 ± 2538.4 2021.5 ± 1106.2 6877.2 ± 2267.9 3283.8 ± 1981.8 2161.5 ± 1187.7 910.1 ± 1004.3 2797.8 ± 1126.5 2335.0 ± 1153.1
6182.4 ± 2449.6 3345.4 ± 3011.8 7904.5 ± 2675.4 6926.2 ± 2462.7 602.7 ± 213.3 712.3 ± 1210.2 1650.6 ± 915.8 1967.4 ± 652.6
⊿
p-Value 5.8
1993.5 −1323.9 −1027.3 −3642.4 1558.8 197.8 1147.2 367.6
b.000 .146 .090 b.000 .004 .187 .015 .134
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Antero-inferior movement of the IPFP was associated with tibial external rotation and patellar lateral translation. This suggests that tibial external rotation induces anterior pressure from the femoral condyle onto the IPFP, causing greater anterior movement. In addition, patellar lateral translation should create space in the medial facet of the PF joint, which might induce IPFP movement into the space in the medial PF joint, causing antero-superior migration of the IPFP. Paulos et al. suggested criteria of IPFP contracture such that Stage 1 involves indurated synovial, fat pad and retinacular tissues, with a painful range of motion, restricted patellar mobility, and quadriceps lag, Stage 2 involves presence of the “shelf sign”, continued peripatellar swelling, and induration with severely restricted patellar tendon, restricted super glide of the patella, and Stage 3 involves developmental patella infera [10]. In a paper reporting the results of surgical release in 28 consecutive cases of IPFP contracture syndrome (IPCS) with a follow-up period of three months to four years, there were 12° increases in extension and 35° increases in the flexion range of motion, followed by PF arthrosis in 80% and patella infera in 16%. Ellen et al. reported a patient with IPFP contracture, who presented with worsening pain and rehabilitation delay [19]. Therefore, it can easily be assumed that IPFP contracture syndrome is induced by inflammation of the IPFP and that stiffness and enlargement of the IPFP reduce patellar mobility and limit quadriceps strength. The current study showed the mobility of the IPFP during quasi-static knee extension, and it would be interesting to compare these findings with the findings in pathological knees with OA or after arthroscopy. We are unaware of the exact causes of the IPFP stiffness or adhesion, some of the factors may include aging, fibrosis after inflammation by injury or repetitive mechanical stress such as repetitive kneeling, KOA with continuous inflammation in the knee joint, trauma, and surgery. Synovial fibrosis of IPFP would occur if IPFP would be with inflammation [20]. Murakami et al.[20] reported increased fibrosis in patients who had pain on exertion or stiffness in squatting after the reconstructive surgery. Adhesion may limit its ability to change its shape during knee movements which induce further mechanical stress on the IPFP. We utilized 3D models of the bones and IPFP obtained by manual segmentation of MRI with a slice pitch of one millimeter. We examined healthy young people without knee pain or history of surgery. Therefore, we consider that these results can be generalized to similar populations without knee pain or history of surgery on the knee. The limitation of this research included the small sample size, which may have introduced beta errors in the results. Since the subjects of this study were young healthy individuals, we should generalize these results to healthy young people only. Segmentation of the IPFP using MRI is sometimes difficult to determine especially at the periphery due to the low contrast between fat and other tissues. The joint positions of 30° and 0° were determined using a goniometer, which may also have introduced some errors. However, despite the above limitations, there is no apparent source of significant bias that would prevent the statement of a firm conclusion. To conclude, the IPFP in the healthy knees moves antero-inferiorly during knee extension. Antero-inferior movement of the IPFP is associated with tibial external rotation and patellar lateral translation. Comparisons of IPFP behavior between healthy and pathological knees in future studies may clarify the role of the IPFP and elucidate problems caused by IPFP contracture. 5. Conclusion In the healthy knee, the IPFP moves antero-inferiorly during knee extension. Antero-inferior movement of the IPFP is associated with tibial external rotation and patellar lateral translation. Comparisons of IPFP behavior between healthy and pathological knees in future studies may clarify the role of the IPFP and elucidate problems caused by IPFP contracture. Contribution Yuriko Okita was involved in data analysis and manuscript writing. Hiroyuki Oba recruited subjects and was involved in data management and analysis. Ryohei Miura recruited subjects and was involved in analysis and manuscript writing. Masashi Morimoto recruited subjects and was involved in data acquisition and analysis. Kazuyoshi Gamada was involved in planning, analysis and manuscript writing. Declaration of competing interest Kazuyoshi Gamada is CEO of GLAB Corp. Inc., which had no influence on this study. No other authors have any conflicting interests to disclose. Acknowledgement The authors received no funding for this study. References [1] Bosomworth NJ. Exercise and knee osteoarthritis: benefit or hazard? Can Fam Physician Sep 2009;55(9):871–8. [2] Gupta S, Hawker GA, Laporte A, Croxford R, Coyte PC. The economic burden of disabling hip and knee osteoarthritis (OA) from the perspective of individuals living with this condition. Rheumatology (Oxford) Dec 2005;44(12):1531–7. [3] Lawrence RC, Helmick CG, Arnett FC, Deyo RA, Felson DT, Giannini EH, et al. Estimates of the prevalence of arthritis and selected musculoskeletal disorders in the United States. Arthritis Rheum May 1998;41(5):778–99. [4] Felson DT. An update on the pathogenesis and epidemiology of osteoarthritis. Radiol Clin North Am Jan 2004;42(1):1–9 [v].
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Please cite this article as: Y. Okita, H. Oba, R. Miura, et al., Movement and volume of infrapatellar fat pad and knee kinematics during quasi-static knee extension ..., The Knee, https://doi.org/10.1016/j.knee.2019.10.019