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Isolated popliteus tendon avulsion in skeletally immature patients
Clinical Radiology (2008) 63, 824e828
PICTORIAL REVIEW
Isolated popliteus tendon avulsion in skeletally immature patients L.D. Wheeler, E.Y.P. Lee, D.C.F. Lloyd* Department of Radiology, University Hospital of Wales, Cardiff, South Glamorgan, Wales, UK Received 21 March 2007; received in revised form 10 August 2007; accepted 22 August 2007
Four cases of isolated popliteus tendon avulsion in skeletally immature patients that presented to our institution over an 11 month period are reviewed. All the cases had characteristic features on the initial knee radiograph and the diagnosis was confirmed using magnetic resonance imaging (MRI). A brief literature review is included. The aim of the present study was to raise awareness of the radiographic findings of isolated popliteus tendon avulsion in adolescent patients. ª 2007 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.
Introduction
Clinical cases
Over an 11-month period, four patients with isolated popliteus tendon avulsion presented to our department with characteristic plain film findings. Other causes of bony fragments around the knee are well documented in standard radiological texts. A fracture of the tibial spine (intercondylar eminence) generally represents an avulsion injury of the anterior cruciate ligament. A bone fragment lying just lateral to the lateral tibial plateau (Segond fracture) represents an avulsion fracture of the lateral tibial plateau by the lateral capsular ligament. This is strongly associated with an anterior cruciate ligament tear and meniscal injuries. A subtle osteochondral fragment that originated from the patello-femoral joint may be the only evidence of a dislocated and relocated patella. Calcification of the medial collateral ligament, which has the eponym PellegrinieStieda, is considered to signify previous trauma to the ligament.1,2 The cases presented here, with bony avulsion of the femoral origin of popliteus, demonstrate consistent radiographic findings that can be readily recognized, but are not described in standard radiology texts.
Four adolescent patients presented to our institution with traumatic knee injuries. Clinically, each patient had a joint effusion and tenderness over the lateral aspect of the knee. All had radiographs that showed a bony fragment at the lateral aspect of the knee and all had MRI confirmation of isolated bony avulsion of the origin of the popliteus tendon (Figs. 1e4). They were all managed conservatively with splinting and physiotherapy and regained full function of the knee. The maximum follow-up was 9 weeks. The clinical details are summarized in Table 1.
* Guarantor and correspondent: D.C.F. Lloyd, Department of Radiology, University Hospital of Wales, Heath Park, Cardiff, South Glamorgan, CF14 4XW, UK. E-mail address: [email protected] (D.C.F. Lloyd).
Discussion The popliteus muscle has a tendinous origin at the anterior end of a groove in the lateral aspect of the lateral femoral condyle inferior to the lateral collateral ligament (Fig. 5). It is a constituent of the posterolateral corner of the knee. The tendon courses infero-medially and the muscle inserts into the postero-medial surface of the proximal tibial metaphysis. The muscle also has origins from the fibular head and the lateral meniscus. The role of the popliteus muscle includes control of lateral meniscal displacement and limiting posterior tibial translation and rotation.3,4
0009-9260/$ - see front matter ª 2007 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.crad.2007.08.014
Figure 1 Case A. (a) Radiograph of the right knee demonstrates avulsed bony fragments (arrow) lateral to the lateral femoral condyle corresponding to the origin of the popliteus tendon.(b-e) Coronal, fat-saturated, fast spin-echo, proton density-weighted images of the right knee, from posterior to anterior, following the popliteus tendon (straight arrow) superiorly and anteriorly along the femoral groove to the site of avulsion (broken arrow) at its origin. The curved arrow indicates the lateral collateral ligament. (f) Sagittal, fast spin-echo proton density weighted image shows the avulsed popliteus tendon (straight arrow) just deep to the lateral collateral ligament (curved arrow), which inserts more superiorly. The broken arrow indicates the fracture site.
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Figure 2 Case B. (a) Left knee radiograph demonstrates an avulsed bony fragment (arrow) lateral to the lateral femoral condyle. (b) Coronal, fat-saturated, fast spin-echo proton density weighted image of the left knee shows the site of bony avulsion at the popliteus tendon origin (broken arrow).
Injury to the popliteus tendon is not uncommon. Brown et al. identified popliteus injury in 1% (24/2412) of consecutive knee MRI examinations in mostly adult patients. However, in only two of
Figure 3 Case C. Radiograph of the left knee demonstrates an avulsed bony fragment (arrow) at the origin of the popliteus tendon.
Figure 4 Case D. Left knee radiograph demonstrates an avulsed bony fragment (arrow) lateral to the lateral femoral condyle.
Isolated popliteus tendon avulsion in skeletally immature patients
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Table 1
Summary of the clinical details of the four adolescent patients
Case
Age
Skeletally Immature
Sex
Knee injured
Circumstance of injury
Mechanism of injury
A B C D
13 14 13 14
Yes Yes Yes Yes
Male Male Male Male
Right Left Left Left
American football injury Football injury Rugby injury Motorcycle accident
Varus rotation Not recorded Tackled Twisting injury
the 24 was popliteus injury an isolated finding, and none of these patients had an avulsion fracture involving the popliteus tendon.5 There are a small number of reported cases of isolated popliteus tendon avulsion as a cause of acute haemarthrosis of the knee. Gruel6 was the
first to identify ‘‘a small fragment in the region of the lateral femoral condyle’’ on plain radiographs in the case of a 15-year-old girl with a twisting injury of the knee. He confirmed an isolated avulsion of the popliteus tendon with an osteochondral fragment on arthroscopy. The present cases were skeletally immature and in their early teens. McConkey postulated that a relative weakness of the bone adjacent to the tendon insertion in children and adolescents (as in the present cases) explains the increased incidence of avulsion injuries in this group.7 Conversely adults are more likely to suffer intrasubstance ruptures.4,5 Radiographs may be normal in cases where the tendon avulsion is not associated with a bony fragment8,9 or there is an intrasubstance tendon rupture.10 The mechanism of injury seems likely to be an anterior translation of the femur on the tibia, with rotation, during knee flexion.7,8 The politeus is a dynamic stabilizer and reflex muscular contraction is likely to contribute to the injury and help explain its isolated nature. Optimal management of these patients has not yet been determined. The present cases were managed conservatively with good outcomes, at least over the limited period of follow-up. Other authors have reported successful results with non-operative management;6,8,10 whereas some argue that operative reattachment of the avulsed tendon is usually straightforward and yields excellent results.7,9 In conclusion, the aim of the present study was to highlight the relatively under-recognized plain film finding of isolated popliteus tendon avulsion. Once this pattern of injury is recognized, it can easily be identified on plain radiographs and MRI can be used to confirm the injury.
References
Figure 5 Illustration of the knee showing the origins of the popliteus muscle (straight arrow) and the lateral collateral ligament (curved arrow).
1. The knee and shafts of the tibia and fibula. In: Rogers LF, editor. Radiology of skeletal trauma. 2nd ed. London: Churchill Livingstone; 1992. p. 1199e317. 2. Skeletal trauma. In: Murray RO, Jacobson HG, Stoker DJ, editors. The Radiology of Skeletal Disorders. 3rd ed. London: Churchill Livingstone; 1990. p. 55e256. 3. Staubli HU, Birrer S. The popliteus tendon and its fascicles at the popliteal hiatus: gross anatomy and functional
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arthroscopic evaluation with and without anterior cruciate ligament deficiency. Arthroscopy 1990;6:209e20. 4. Harner CD, Hoher J, Vogrin TM, et al. The effects of a popliteus muscle load on in situ forces in the posterior cruciate ligament and on knee kinematics. A human cadaveric study. Am J Sports Med 1998;26:669e73. 5. Brown TR, Quinn SF, Wensel JP, et al. Diagnosis of popliteus injuries with MR imaging. Skeletal Radiol 1995;24:511e4. 6. Gruel JB. Isolated avulsion of the popliteus tendon. Arthroscopy 1990;6:94e5.
L.D. Wheeler et al.
7. McConkey JP. Avulsion of the popliteus tendon. J Pediatr Orthop 1991;11:230e3. 8. Naver L, Aalberg JR. Avulsion of the popliteus tendon. A rare cause of chondral fracture and hemarthrosis. Am J Sports Med 1985;13:423e4. 9. Garth Jr WP, Pomphrey Jr MM, Merrill KD. Isolated avulsion of the popliteus tendon: Operative repair. A report of two cases. J Bone Joint Surg Am 1992;74:130e2. 10. Conroy J, King D, Gibbon A. Isolated rupture of the popliteus tendon in a professional soccer player. Knee 2004;11:67e90.
PICTORIAL REVIEW
Isolated popliteus tendon avulsion in skeletally immature patients L.D. Wheeler, E.Y.P. Lee, D.C.F. Lloyd* Department of Radiology, University Hospital of Wales, Cardiff, South Glamorgan, Wales, UK Received 21 March 2007; received in revised form 10 August 2007; accepted 22 August 2007
Four cases of isolated popliteus tendon avulsion in skeletally immature patients that presented to our institution over an 11 month period are reviewed. All the cases had characteristic features on the initial knee radiograph and the diagnosis was confirmed using magnetic resonance imaging (MRI). A brief literature review is included. The aim of the present study was to raise awareness of the radiographic findings of isolated popliteus tendon avulsion in adolescent patients. ª 2007 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.
Introduction
Clinical cases
Over an 11-month period, four patients with isolated popliteus tendon avulsion presented to our department with characteristic plain film findings. Other causes of bony fragments around the knee are well documented in standard radiological texts. A fracture of the tibial spine (intercondylar eminence) generally represents an avulsion injury of the anterior cruciate ligament. A bone fragment lying just lateral to the lateral tibial plateau (Segond fracture) represents an avulsion fracture of the lateral tibial plateau by the lateral capsular ligament. This is strongly associated with an anterior cruciate ligament tear and meniscal injuries. A subtle osteochondral fragment that originated from the patello-femoral joint may be the only evidence of a dislocated and relocated patella. Calcification of the medial collateral ligament, which has the eponym PellegrinieStieda, is considered to signify previous trauma to the ligament.1,2 The cases presented here, with bony avulsion of the femoral origin of popliteus, demonstrate consistent radiographic findings that can be readily recognized, but are not described in standard radiology texts.
Four adolescent patients presented to our institution with traumatic knee injuries. Clinically, each patient had a joint effusion and tenderness over the lateral aspect of the knee. All had radiographs that showed a bony fragment at the lateral aspect of the knee and all had MRI confirmation of isolated bony avulsion of the origin of the popliteus tendon (Figs. 1e4). They were all managed conservatively with splinting and physiotherapy and regained full function of the knee. The maximum follow-up was 9 weeks. The clinical details are summarized in Table 1.
* Guarantor and correspondent: D.C.F. Lloyd, Department of Radiology, University Hospital of Wales, Heath Park, Cardiff, South Glamorgan, CF14 4XW, UK. E-mail address: [email protected] (D.C.F. Lloyd).
Discussion The popliteus muscle has a tendinous origin at the anterior end of a groove in the lateral aspect of the lateral femoral condyle inferior to the lateral collateral ligament (Fig. 5). It is a constituent of the posterolateral corner of the knee. The tendon courses infero-medially and the muscle inserts into the postero-medial surface of the proximal tibial metaphysis. The muscle also has origins from the fibular head and the lateral meniscus. The role of the popliteus muscle includes control of lateral meniscal displacement and limiting posterior tibial translation and rotation.3,4
0009-9260/$ - see front matter ª 2007 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.crad.2007.08.014
Figure 1 Case A. (a) Radiograph of the right knee demonstrates avulsed bony fragments (arrow) lateral to the lateral femoral condyle corresponding to the origin of the popliteus tendon.(b-e) Coronal, fat-saturated, fast spin-echo, proton density-weighted images of the right knee, from posterior to anterior, following the popliteus tendon (straight arrow) superiorly and anteriorly along the femoral groove to the site of avulsion (broken arrow) at its origin. The curved arrow indicates the lateral collateral ligament. (f) Sagittal, fast spin-echo proton density weighted image shows the avulsed popliteus tendon (straight arrow) just deep to the lateral collateral ligament (curved arrow), which inserts more superiorly. The broken arrow indicates the fracture site.
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Figure 2 Case B. (a) Left knee radiograph demonstrates an avulsed bony fragment (arrow) lateral to the lateral femoral condyle. (b) Coronal, fat-saturated, fast spin-echo proton density weighted image of the left knee shows the site of bony avulsion at the popliteus tendon origin (broken arrow).
Injury to the popliteus tendon is not uncommon. Brown et al. identified popliteus injury in 1% (24/2412) of consecutive knee MRI examinations in mostly adult patients. However, in only two of
Figure 3 Case C. Radiograph of the left knee demonstrates an avulsed bony fragment (arrow) at the origin of the popliteus tendon.
Figure 4 Case D. Left knee radiograph demonstrates an avulsed bony fragment (arrow) lateral to the lateral femoral condyle.
Isolated popliteus tendon avulsion in skeletally immature patients
827
Table 1
Summary of the clinical details of the four adolescent patients
Case
Age
Skeletally Immature
Sex
Knee injured
Circumstance of injury
Mechanism of injury
A B C D
13 14 13 14
Yes Yes Yes Yes
Male Male Male Male
Right Left Left Left
American football injury Football injury Rugby injury Motorcycle accident
Varus rotation Not recorded Tackled Twisting injury
the 24 was popliteus injury an isolated finding, and none of these patients had an avulsion fracture involving the popliteus tendon.5 There are a small number of reported cases of isolated popliteus tendon avulsion as a cause of acute haemarthrosis of the knee. Gruel6 was the
first to identify ‘‘a small fragment in the region of the lateral femoral condyle’’ on plain radiographs in the case of a 15-year-old girl with a twisting injury of the knee. He confirmed an isolated avulsion of the popliteus tendon with an osteochondral fragment on arthroscopy. The present cases were skeletally immature and in their early teens. McConkey postulated that a relative weakness of the bone adjacent to the tendon insertion in children and adolescents (as in the present cases) explains the increased incidence of avulsion injuries in this group.7 Conversely adults are more likely to suffer intrasubstance ruptures.4,5 Radiographs may be normal in cases where the tendon avulsion is not associated with a bony fragment8,9 or there is an intrasubstance tendon rupture.10 The mechanism of injury seems likely to be an anterior translation of the femur on the tibia, with rotation, during knee flexion.7,8 The politeus is a dynamic stabilizer and reflex muscular contraction is likely to contribute to the injury and help explain its isolated nature. Optimal management of these patients has not yet been determined. The present cases were managed conservatively with good outcomes, at least over the limited period of follow-up. Other authors have reported successful results with non-operative management;6,8,10 whereas some argue that operative reattachment of the avulsed tendon is usually straightforward and yields excellent results.7,9 In conclusion, the aim of the present study was to highlight the relatively under-recognized plain film finding of isolated popliteus tendon avulsion. Once this pattern of injury is recognized, it can easily be identified on plain radiographs and MRI can be used to confirm the injury.
References
Figure 5 Illustration of the knee showing the origins of the popliteus muscle (straight arrow) and the lateral collateral ligament (curved arrow).
1. The knee and shafts of the tibia and fibula. In: Rogers LF, editor. Radiology of skeletal trauma. 2nd ed. London: Churchill Livingstone; 1992. p. 1199e317. 2. Skeletal trauma. In: Murray RO, Jacobson HG, Stoker DJ, editors. The Radiology of Skeletal Disorders. 3rd ed. London: Churchill Livingstone; 1990. p. 55e256. 3. Staubli HU, Birrer S. The popliteus tendon and its fascicles at the popliteal hiatus: gross anatomy and functional
828
arthroscopic evaluation with and without anterior cruciate ligament deficiency. Arthroscopy 1990;6:209e20. 4. Harner CD, Hoher J, Vogrin TM, et al. The effects of a popliteus muscle load on in situ forces in the posterior cruciate ligament and on knee kinematics. A human cadaveric study. Am J Sports Med 1998;26:669e73. 5. Brown TR, Quinn SF, Wensel JP, et al. Diagnosis of popliteus injuries with MR imaging. Skeletal Radiol 1995;24:511e4. 6. Gruel JB. Isolated avulsion of the popliteus tendon. Arthroscopy 1990;6:94e5.
L.D. Wheeler et al.
7. McConkey JP. Avulsion of the popliteus tendon. J Pediatr Orthop 1991;11:230e3. 8. Naver L, Aalberg JR. Avulsion of the popliteus tendon. A rare cause of chondral fracture and hemarthrosis. Am J Sports Med 1985;13:423e4. 9. Garth Jr WP, Pomphrey Jr MM, Merrill KD. Isolated avulsion of the popliteus tendon: Operative repair. A report of two cases. J Bone Joint Surg Am 1992;74:130e2. 10. Conroy J, King D, Gibbon A. Isolated rupture of the popliteus tendon in a professional soccer player. Knee 2004;11:67e90.