The effect of low-load exercise on joint pain, function, and activities of daily living in patients with knee osteoarthritis

THEKNE-02560; No of Pages 11 The Knee xxx (2017) xxx–xxx

Contents lists available at ScienceDirect

The Knee

The effect of low-load exercise on joint pain, function, and activities of daily living in patients with knee osteoarthritis☆,☆☆ Jason Peeler a,b,⁎, Jacquie Ripat c a b c

Max Rady College of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada Pan Am Clinic, Winnipeg, Manitoba, Canada College of Rehabilitation Sciences, University of Manitoba, Winnipeg, Manitoba, Canada

a r t i c l e

i n f o

Article history: Received 29 May 2017 Received in revised form 17 November 2017 Accepted 9 December 2017 Available online xxxx Keywords: Exercise Lower body positive pressure (LBPP) Activities of daily living Pain Knee osteoarthritis

a b s t r a c t Background: Knee osteoarthritis has a lifetime risk of nearly one in two, with obese individuals being most susceptible. While exercise is universally recognized as a critical component for management, unsafe or ineffective exercise frequently leads to exacerbation of joint symptoms. Aim: Evaluate the effect of a 12 week lower body positive pressure (LBPP) supported low-load treadmill walking program on knee pain, joint function, and performance of daily activities in patients with knee osteoarthritis (OA). Design: Prospective, observational, repeated measures investigation. Setting: Community based, multidisciplinary musculoskeletal medicine clinic. Patients: Thirty-one patients, aged 50–75, with a BMI ≥25 kg/m2 and radiographic confirmed mild to moderate knee OA. Intervention: Twelve week LBPP treadmill walking exercise regimen. Outcome measures: The Knee Injury and Osteoarthritis Outcome Score (KOOS) and the Canadian Occupational Performance Measure (COPM) were used to quantify joint symptoms and patient function; isokinetic thigh muscle strength was evaluated; and a 10-point VAS was used to quantify acute knee pain while walking. Baseline and follow-up data were compared in order to examine the effect of the 12 week exercise intervention. Results: There was a significant difference between baseline and follow-up data: KOOS and COPM scores both improved; thigh muscle strength increased; and acute knee pain during full weight bearing walking diminished significantly. Conclusions: Participation in a 12 week LBPP supported treadmill walking exercise regimen significantly enhanced patient function and quality of life, as well as the ability to perform activities of daily living that patient's self-identified as being important, yet difficult to perform. © 2017 Elsevier B.V. All rights reserved.

1. Introduction Knee osteoarthritis (OA) is the most common form of arthritis in the world [1]. The World Health Organization (1997) reports it as the fourth and eighth most common cause of disability in women and men, respectively [2]. At present, the rate of knee OA is as high as that of cardiac disease, and it is the most prevalent medical condition in individuals over the age of 65 [3]. Disease progression is characterized by the gradual and debilitating onset of joint pain and stiffness. Patients experience progressive loss

☆ Ethics approvalThis investigation received university ethics board approval and was authorized by the local regional health authority. ☆☆ Financial disclosureThe authors have no conflict of interest to report, and received no financial aid from the equipment manufacturer. We certify that no party having a direct interest in the results of this investigation has or will confer a benefit on us or on any organization with which we are associated. ⁎ Corresponding author at: Max Rady College of Medicine, University of Manitoba, 102-745 Bannatyne Ave., Winnipeg, Manitoba, Canada. E-mail address: [email protected] (J. Peeler).

https://doi.org/10.1016/j.knee.2017.12.003 0968-0160/© 2017 Elsevier B.V. All rights reserved.

Please cite this article as: Peeler J, Ripat J, The effect of low-load exercise on joint pain, function, and activities of daily living in patients with knee osteoarthritis, Knee (2017), https://doi.org/10.1016/j.knee.2017.12.003

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of joint function that makes it difficult to perform essential activities of daily living such as walking, squatting, and going up and down stairs [4]. Research indicates that exercise can play an important role in the management of symptoms associated with knee OA progression, as well as enhance a patient's functional capacity during normal activities of daily living [5]. Unfortunately, unsafe or ineffective exercise frequently leads to exacerbation of joint symptoms, results in poor adherence and high drop-out rates. This leads to an increased reliance on pharmacological regimes that can place the patient at significant risk for the development of other co-morbidities [6]. The emergence of a new exercise treadmill which utilizes a technology called lower body positive-pressure (LBPP) now permits patients suffering from lower extremity pathologies to perform low-load exercise without risk of exacerbation of symptoms [7]. The treadmill uses a waist-high air chamber filled with positive air-pressure (i.e. LBPP) to accurately and reliably diminish body weight during exercise (Figure 1) [8–10]. Thus far, LBPP exercise interventions have been used to successfully accelerate the rehabilitation of patients following meniscectomy and anterior cruciate ligament reconstruction [7], as well as lower extremity trauma [11]. Our research group has previously investigated the feasibility of using the LBPP technology as a means to remediate weight-bearing exercise for overweight patients with knee OA at significant risk for exacerbation of joint symptoms following exercise [12]. Data from this investigation suggested that LBPP supported low-load walking could be used to facilitate safe, user-friendly treadmill walking by knee OA patients without risk of exacerbation of joint symptoms, and facilitated the development of a precise LBPP supported exercise methodology that is appropriate for at-risk patient populations. These results also laid the foundation for our research group to begin safe exploration of the long-term impact of exercise on knee OA progression and pathogeneses. This data should help to guide the development and refinement of evidence based exercise strategies that can be used to more effectively manage day-to-day joint symptoms, delay disease progression, and lead to an improvement in the overall physical health, quality of life and social well-being of North America's aging population. 2. Purpose of the investigation The purpose of this study was to examine the effect of a 12 week LBPP supported low-load walking exercise regime on knee pain, joint function, thigh strength and ability to perform normal activities of daily living in both male and female patients with knee OA. 3. Methods 3.1. Setting and participants Following ethics review and approval by the local regional health authority, 31 overweight participants between the ages of 50 and 75, with symptomatic mild–moderate knee OA were recruited to participate in the study from the patient population of the local Regional Health Authority's Centre of Excellence for Musculoskeletal Care. Inclusion criteria were: (1) body mass index (BMI)

Figure 1. Subject walking on the G-trainer treadmill.

Please cite this article as: Peeler J, Ripat J, The effect of low-load exercise on joint pain, function, and activities of daily living in patients with knee osteoarthritis, Knee (2017), https://doi.org/10.1016/j.knee.2017.12.003

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≥25 kg/m2; (2) knee pain when performing normal activities of daily living (such as walking, squatting, or kneeling); and (3) radiographic evidence of mild to moderate (Kellgren & Lawrence grades II or III) knee OA in one or both knees. Knee OA severity was confirmed via antero-posterior radiographs taken for all subjects in a weight-bearing position with both knees in five degrees of flexion, and scored by the same senior musculoskeletal radiologist using the Kellgren–Lawrence scale [13]. Radiographic evaluation was used to determine patient knee joint alignment, and to categorize patients anthropometrically into three groups (normal/varus/valgus) [14]. In the cases of bilateral knee OA, the more symptomatic knee (as determined from scoring on a baseline Knee Injury and Osteoarthritis Outcome Score questionnaire) was designated as the affected knee. For the purpose of all pre- and post-assessments, the participant was instructed to base their responses on only the affected knee [15]. Exclusion criteria included: (1) Kellgren & Lawrence grade III+ radiographic evidence of severe knee OA; (2) history (within the last year) of traumatic hip, knee, or ankle injury or surgery; (3) history (within the last year) of treatment on the affected knee that involved joint injection or physiotherapy; (4) use of crutches or a walking aid during ambulation; (5) history of medical conditions that would prevent physical activity; and (6) history of cardiovascular disease, or screen positive for ankylosing spondylitis, psoriatic arthritis, chronic reactive arthritis, or renal problems requiring peritoneal dialysis or hemodialysis. Prior to initiation of participation in the study, each participant was assigned an identification (I.D.) number, and required to complete informed consent and knee demographic forms which provided a detailed history of the participant's knee OA (including any past or current medications). For patients currently on medication, they were asked to report any changes which occurred over the course of the 12 week intervention.

3.2. Pre- and post-assessment of knee joint function The investigation utilized a prospective, observational, repeated measures design. Testing was completed immediately before and following participant's completion of a 12 week LBPP supported treadmill walking program [12]. All testing was carried out in the same research facility and under similar environment conditions, and according to previously described methodologies [12,16–18]. Scoring from the baseline Knee Injury and Osteoarthritis Outcome Score questionnaire was used to determine each participant's affected knee for the study. All participants were instructed to wear shorts and t-shirts, as well as the same athletic footwear for all testing and exercise sessions. Pre- and post-testing consisted of five components: 1. anthropometric evaluation; 2. evaluation of quadriceps muscle strength; 3. evaluation of acute knee pain during full weight bearing walking; 4. subjective evaluation of knee joint pain and function using a Knee Injury and Osteoarthritis Outcome Score questionnaire and 5. evaluation of performance and satisfaction of performance in self-identified functional activities using the Canadian Occupational Performance Measure. The same evaluator/occupational therapist completed each participant's pre- and post-testing sessions during the study, as well as directly supervised the 12 week low-load exercise regime. This individual was also blinded to all patient test scores, as well as to which knee the participant had designated as their affected knee for the study. All anthropometric measurements were collected in the same orthopedic clinic (using the same equipment). Patient height (meters) and body mass (kilograms) were measured using a Seca 700 Beam Scale (Seca, Birmingham, UK) equipped with a stadiometer. Measurements were taken with shoes off and participant height was measured at the peak of inhalation. Height and body mass measurements were used to calculate BMI (body mass (kg/height squared (m2)). Quadriceps muscle strength was measured using the Biodex System 3 isokinetic system (Biodex Corporation, Shirley, NY, USA). The strength testing protocol was based on previously described methodologies [19,20], with the order of testing (left vs. right limb) being randomized. Participants were tested in a seated position and instructed to perform four repetitions of knee extension at three increasing speeds (60, 180, and 240°/s). Participants began by performing a 50% effort warm-up at each speed, and then were required to perform the bilateral testing protocol using maximal exertion. The peak torque (measured in Newton-meters (N-m) achieved over the four repetitions was the recorded score. In order to obtain a relative strength score for comparison between subjects, peak torque (N-m) was divided by body weight (kg) to obtain a strength ratio (N-m/kg). A 10-point Visual Analog Scale (VAS) was used to measure the acute knee pain of a participant's affected knee while performing a 30 minute full weight bearing (FWB) treadmill walking session at a walking speed of 3.1 mph and 0° incline. Following a five minute warm-up period, VAS measures (to the nearest whole number) were recorded at five minute intervals (at minutes 10, 15, 20, 25, & 30) during each walking session, and later averaged in order to obtain a session specific acute knee pain score for each participant's affected knee. A Knee Injury and Osteoarthritis Outcome Score (KOOS) questionnaire was administered according to previously described methodologies [16]. The KOOS is a patient-reported outcome measurement instrument that is commonly used by researchers and clinicians for evaluating changes after different exercise interventions [21,22]. It is a self-administered and standardized questionnaire that provides a valid and highly reliable assessment of a patient's knee joint function and associated problems [16,22]. Scoring on the KOOS can range from 0 (complete disability) to 100 (no disability) and is evaluated using five categories: (1). Pain; (2). Symptoms; (3). Activities of Daily Living; (4). Function, Sports and Recreational Activities; and (5). Quality of Life [16,22]. The Canadian Occupational Performance Measure (COPM) is an individualized, client-centered outcome measure designed to detect changes in occupational performance over time in activities that the individual has self-identified as being important and difficult to perform [17]. The COPM has well-established psychometric properties including validity, reliability, and responsiveness to change [23], and is widely used in occupational therapy practice to detect changes in the degree of satisfaction and performance due to treatment [17]. Each participant's assessment took between 30 and 60 min to complete, and was conducted according to the standardized protocol outlined in the COPM manual by the same licensed occupational therapist [23]. Scoring was Please cite this article as: Peeler J, Ripat J, The effect of low-load exercise on joint pain, function, and activities of daily living in patients with knee osteoarthritis, Knee (2017), https://doi.org/10.1016/j.knee.2017.12.003

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calculated as per the administration instructions, and a frequency count of the occupational performance issues identified on the COPMs was organized into the three categories: (1) leisure; (2) self-care; and (3) productivity. 3.3. Exercise regime Following completion of the baseline evaluation, participants completed a 12 week LBPP supported treadmill walking regimen according to previously described methodologies [12]. Briefly, participants exercised two times per week for 30 min on a GTrainer treadmill (Alter G Inc.) at a set speed of 3.1 mph at 0° incline (Figure 1). For each exercise session, LBPP support was added in five percent increments each minute until one of the following criteria were met: (1) acute knee pain levels reached 0/10 on the VAS; (2) no further decreases in pain were achieved; and (3) LBPP support was restricted to a maximum of 40% body weight. Visual Analog Scale scoring of acute knee pain was monitored at five minute intervals over the duration of each low-load treadmill walking session, with the LBPP pressure being constantly monitored and adjusted in one percent increments in order to maintain a comfortable walking experience. Participants were blinded to the percentage of LBPP used to un-weight them during each low-load walking session. The treadmill's LBPP blower and air chamber were on and pressurized even when participants were performing walking sessions with 0% LBPP support. Post-exercise testing was completed in the week which immediately followed completion of each participant's walking exercise regime, and at a time which corresponded to the participant's regular exercise time (i.e. if a patient's regular exercise time was scheduled for Tuesday and Thursday mornings over the 12 week intervention, then their follow-up testing session was also scheduled in this time slot). The post-exercise testing session was completed in a manner that was consistent with pre-testing protocols, and all subjects were required to complete post-testing within seven days of completing the 12 week exercise intervention (or their data would be disqualified from inclusion in the study). 3.4. Statistical analysis Microsoft Office Excel 2007 with the Analysis ToolPak add-in, StatPlus:Mac 2009, and SPSS v.20 were used for data analysis. Paired t-tests were used to compare pre- and post-test results for anthropometry, and quadriceps strength. Wilcoxon signedrank tests were used to compare VAS scores from FWB walking, KOOS and COPM scoring. Differences were considered statistically significant if p b 0.05. Pearson product correlations were used to determine the relationship between performance and satisfaction with performance on COPM measures from baseline and follow-up assessments, with r values below 0.60 indicative of a low level of correlation, values between 0.60 and 0.80 suggesting a moderate level of correlation, and values above 0.80 considered a high level of correlation [24]. The changes in COPM performance scores between baseline and follow-up testing were also correlated with the changes in scoring on each KOOS subscale. 4. Results Descriptive data for study participants are summarized in Table 1. Mean (±SD) age of the 31 participants (22 female/nine male) was 64.2 (±6.2) years. Knee demographic data illustrated that all but three participants demonstrated radiographically confirmed OA bilaterally. With one exception, all of the participants were right-leg dominant. For 17 of the participants, their dominant leg was their affected knee, and for the remaining 14, their non-dominant leg was their affected knee. With regard to previous treatment strategies, 71% of participants reported having physiotherapy, 42% used knee bracing, 32% used anti-inflammatory medication, and 12% had previously received intra-articular injections for the management of symptoms. At the time of the study, no participants had received physiotherapy treatment or intra-articular injections within the past year. Anthropometric measurements taken at baseline indicated that participants had an average height of 1.66 m, weight of 90.4 kg, and BMI of 32.8 kg/m2. Comparisons of pre- vs. post-testing anthropometry are presented in Table 2. Data illustrated that both male and female participants experienced no significant changes in body anthropometry over the course of the investigation. Isokinetic quadriceps strength data expressed as a ratio of peak torque in Newton-meters to body weight in kilograms (N-m/ kg) are presented in Table 3. No significant differences were observed between the affected and non-affected limbs. Significant increases in strength were observed between baseline and follow-up testing at all three isokinetic testing speeds for female

Table 1 Demographic information for study participants. Demographic

Male

Female

Total

Number of subjects Age (years) Duration of symptoms (months) Affected knee (uni/bilateral) OA severity (mild/moderate)

9 67.1 ± 6.4 (59–75) 65.0 ± 54.0 (9–156) 0/9 2/7

22 63.1 ± 5.9 (53–72) 68.0 ± 78.0 (4–372) 3/19 10/12

31 64.2 ± 6.2 (53.0–75.0) 66.0 ± 70.0 (4–372) 3/28 12/19

Mean ± SD (range).

Please cite this article as: Peeler J, Ripat J, The effect of low-load exercise on joint pain, function, and activities of daily living in patients with knee osteoarthritis, Knee (2017), https://doi.org/10.1016/j.knee.2017.12.003

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Table 2 Anthropometric measurements from baseline and follow-up assessment. Anthropometry

Baseline

Height (m) Weight (kg) BMI (kg/m2) Leg alignment Varus/valgus/normal

Follow-up

Male

Female

Total

Male

Female

Total

1.74 ± 0.08 91.2 ± 16.6 29.9 ± 4.3 8/1/0

1.63 ± 0.06 90.0 ± 17.8 34.0 ± 7.0 11/8/3

1.66 ± 0.08 90.4 ± 17.2 32.8 ± 6.5 19/9/3

1.74 ± 0.08 90.5 ± 17.3 29.8 ± 4.5 8/1/0

1.63 ± 0.06 89.4 ± 18.0 33.8 ± 7.1 11/8/3

1.66 ± 0.08 89.7 ± 17.5 32.6 ± 6.6 19/9/3

Mean ± SD.

subjects. While an upward trend in the quadriceps strength of male participants was observed when comparing pre- and postexercise data, the amount of change was not statistically significant. Data for the total group were consistent with results organized by sex, and indicated that there were significant differences between baseline and follow-up strength scores at all testing speeds. Visual Analog Scoring of acute knee pain during the baseline and follow-up FWB treadmill walking sessions is depicted in Table 4. Data indicate that acute knee pain levels for the total group (mean ± SD) significantly decreased (p = 0.0001) as a result of the 12 week LBPP intervention. Data indicated that both genders experienced significantly less knee pain during the follow-up FWB testing session, with the female group demonstrating the largest change (seven of the eight participants who were able to walk pain-free on follow-up evaluation were female). Table 4 also depicts Visual Analog Scoring of acute knee pain during the 1st and last (24th) 30 min LBPP supported treadmill exercise sessions. Data suggest that both males and females experienced significantly less acute knee pain when exercising during the last exercise session of the 12 week intervention (as compared to the 1st session). Data indicate that the amount of LBPP support required to eliminate knee pain over the 12 week intervention also significantly decreased (p N 0.002) from 17.9% (±9.4) during the first treadmill walking session to 8.5% (±8.3) during the last treadmill walking session, with eight participants (26% of the sample) able to walk pain-free (with no LBPP support what-so-ever) by the end of the 12 week intervention. The KOOS scores from baseline and follow-up evaluation are presented in Table 5. Following the completion of the 12 week walking regimen, improvements in KOOS follow-up testing scores were noted for all subjects, but these changes were significant for males on only two subscales (Sport/Rec and QOL), while the female group experienced significant changes in follow-up test scores across all five sub-scales. It is important to note that the Sport/Rec subscale evaluated activities such as running, jumping, squatting, pivoting, and kneeling. In this study, many of the Sport/Rec questions were not answered because participants felt that a question was not applicable to their lifestyle. In instances where more than two questions in the Sport/Rec subscale had missing data, the subscale score was not calculated [25]. As a result, only 19 subjects provided usable data for statistical analysis of Sport/ Rec subscale. COPM data from baseline and follow-up evaluation are presented in Table 6. Overall, COPM scoring for self-identified activities suggested that participants experienced a significant change in both performance, and satisfaction with performance, following completion of the 12 week walking regimen. Data also illustrated that a moderate level of correlation (r = 0.70) existed between patient performance, and satisfaction with performance at baseline evaluation. Following completion of the 12 week walking regimen, the strength of this relationship increased to a high level of correlation (r = 0.83). In total, 149 activities were identified by participants during the baseline COPM interview as posing difficulty. Forty percent of the identified issues were categorized as leisure; 38% of identified activities were categorized as related to self-care; and 22% of the activities posed difficulty in the area of productivity. Figure 2a, b and c provides a visual illustration of the activities that were most commonly identified by participants. Within the leisure category (Figure 2a), 25% of participants identified walking as the #1 activity that posed the greatest difficulty. This was followed by other leisure activities such as traveling — 15%; gardening and playing with grandchildren — 12% each; golf — nine percent; lower body activities such as jogging, dancing, skiing or Table 3 Quadriceps muscle strength for the affected knee (expressed in N-m/kg) from baseline and follow-up assessment. Baseline

Male (N = 9) Female (N = 22) Total (N = 31)

Follow-up

60°

180°

240°

60°

180°

240°

0.99 ± 0.42

0.64 ± 0.24

0.56 ± 0.26

0.63 ± 0.26

0.36 ± 0.20

0.33 ± 0.20

0.74 ± 0.35

0.45 ± 0.24

0.40 ± 0.24

1.11 ± 0.28 (p = 0.2391) 0.74 ± 0.22⁎⁎ (p = 0.0051) 0.86 ± 0.29⁎⁎

0.74 ± 0.17 (p = 0.0751) 0.51 ± 0.16⁎⁎ (p = 0.0006) 0.58 ± 0.19⁎⁎

0.64 ± 0.19 (p = 0.0913) 0.44 ± 0.14⁎⁎ (p = 0.0032) 0.50 ± 0.18⁎⁎

(p = 0.0024)

(p = 0.0001)

(p = 0.0001)

Mean ± SD. ⁎⁎ p b 0.01, (p-value).

Please cite this article as: Peeler J, Ripat J, The effect of low-load exercise on joint pain, function, and activities of daily living in patients with knee osteoarthritis, Knee (2017), https://doi.org/10.1016/j.knee.2017.12.003

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Table 4 Pain in the affected knee during treadmill walking sessions.

Male (N = 9) Female (N = 22) Total

Baseline FWB walking

Follow-up FWB walking

1st LBPP Walking session

24th LBPP Walking session

4.0 ± 2.0

2.8 ± 2.1⁎ (p = 0.0490) 1.0 ± 1.3⁎⁎ (p = 0.0002) 1.6 ± 1.8⁎⁎

3.7 ± 1.9

2.2 ± 1.9⁎ (p = 0.0464) 1.6 ± 2.0⁎⁎ (p = 0.0098) 1.8 ± 2.0⁎

2.9 ± 2.2 3.2 ± 2.1

2.3 ± 1.7 2.6 ± 1.8

(p = 0.0001)

(p = 0.0344)

Comparison of participant knee pain as measured by the Visual Analog Scale (mm) for 30 min of treadmill walking under FWB walking and LBPP supported walking conditions. Mean ± SD. ⁎⁎ p b 0.01, (p-value). ⁎ p b 0.05, (p-value).

baseball — eight percent; exercise classes — seven percent; canoeing/outdoor activities — five percent, volunteering in community — three percent, and sitting to sing in choir, or to play bridge — two percent each. Within the self-care category (Figure 2b), 35% of participants identified going up and down stairs as the activity which posed the greatest dilemma. Other activities which posed a significant challenge were bathtub transfers — 18%; car transfers — 14%; sit to stand actions — 14%; lower body dressing (i.e. putting on socks or shoes) — 10%; and kneeling or squatting — nine percent. In terms of productivity (Figure 2c), the completion of routine household duties such as cooking, cleaning and laundry was identified by participants as posing the greatest challenges — 28%. Other activities related to daily productivity included cooking meals — 25%, shopping — 22%, yard work — 13%; taking care of grandchildren — six percent; and office work or prolonged sitting at a job (three percent each). Finally, Figure 3 provides a visual depiction of the relationship between changes in KOOS scoring and changes in COPM performance scores observed between baseline and follow-up testing. Pearson correlation testing revealed that the change in the COPM performance score was moderately correlated with a change in the KOOS subscales of Pain (r = 0.65), and Activities of Daily Living (r = 0.65). Additionally, while there was a positive trend in the relationship between the COPM performance score and other KOOS subscales such as Quality of Life (QOL), Joint Symptoms, and Sport/Rec activities, statistically these relationships illustrated only a low level of correlation (QOL: r = 0.39; Joint Symptoms: r = 0.35; Sport/Rec: r = 0.39) between KOOS and COPM measures.

Table 5 KOOS scoring for the affected knee from baseline and follow-up assessment. Baseline

Follow-up

KOOS

Male

Female

Total

Male

Female

Total

Pain N = 31 Symptoms N = 31 ADL N = 31 Sport/Rec N = 19 QOL N = 31

50 ± 13

55 ± 11

54 ± 12

56 ± 16

54 ± 12

54 ± 13

58 ± 10

58 ± 15

58 ± 14

38 ± 18

20 ± 14

27 ± 19

35 ± 11

31 ± 13

32 ± 13

54 ± 17 (p = 0.2846) 60 ± 16 (p = 0.1930) 63 ± 21 (p = 0.2528) 51 ± 16⁎ (p = 0.0235) 47 ± 11⁎ (p = 0.0116)

62 ± 14⁎⁎ (p = 0.0050) 64 ± 18⁎⁎ (p = 0.0013) 67 ± 15⁎⁎ (p = 0.0016) 42 ± 21⁎⁎ (p = 0.0001) 45 ± 15⁎⁎ (p = 0.0016)

60 ± 15⁎ (p = 0.0200) 63 ± 17⁎⁎ (p = 0.0019) 66 ± 17⁎⁎ (p = 0.0076) 45 ± 24⁎⁎ (p = 0.0033) 46 ± 14⁎⁎ (p = 0.0002)

Mean ± SD. ⁎⁎ p b 0.01, (p-value). ⁎ p b 0.05, (p-value).

Table 6 COPM scores for the affected knee from baseline and follow-up assessment. Baseline Subscale

Male

Follow-up Female

Total

Male

Female

Total

6.2 ± 2.5⁎ (p = 0.0415) 6.2 ± 2.8⁎ (p = 0.0205)

5.3 ± 1.6⁎⁎ (p = 0.0003) 4.5 ± 1.6⁎⁎ (p = 0.0003)

5.5 ± 1.9⁎⁎ (p = 0.0001) 5.0 ± 2.2⁎⁎ (p = 0.0001)

Performance

5.0 ± 1.6

4.3 ± 1.5

4.5 ± 1.5

Satisfaction with performance

4.3 ± 1.8

3.0 ± 1.3

3.4 ± 1.6

Mean ± SD. ⁎⁎ p b 0.01, (p-value). ⁎ p b 0.05, (p-value).

Please cite this article as: Peeler J, Ripat J, The effect of low-load exercise on joint pain, function, and activities of daily living in patients with knee osteoarthritis, Knee (2017), https://doi.org/10.1016/j.knee.2017.12.003

Figure 2. a, b, c. Leisure, self care and productivity activities identified by participants during COPM interviews.

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a

c

b

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Please cite this article as: Peeler J, Ripat J, The effect of low-load exercise on joint pain, function, and activities of daily living in patients with knee osteoarthritis, Knee (2017), https://doi.org/10.1016/j.knee.2017.12.003

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Figure 3. Relationship between COPM and KOOS scoring.

5. Discussion The purpose of this investigation was to evaluate the effect of a 12 week LBPP supported low-load exercise program on knee pain, joint function, and performance of daily activities in over-weight patients with knee OA. Data suggest that the exercise regimen helped to enhanced patient function, diminished acute knee pain during full-weight bearing walking, increased thigh muscle Please cite this article as: Peeler J, Ripat J, The effect of low-load exercise on joint pain, function, and activities of daily living in patients with knee osteoarthritis, Knee (2017), https://doi.org/10.1016/j.knee.2017.12.003

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strength, and most importantly, improved the ability of participants to perform activities of daily living that they had self-identified as being important, yet difficult to perform. These findings have important implications for the development and refinement of exercise strategies and interventions used to manage symptoms and improve joint function in over-weight patients diagnosed with knee OA. Patient demographics for the current investigation are similar to those previously reported in the knee OA literature [26,27]. The majority of participants were female, and representative of an aging, sedentary patient population who experienced significant pain and impairment during normal activities of daily living. A large percentage of the participants reported avoiding activities such as running, jumping, and kneeling, as well as walking up and down stairs. Anthropometric data illustrated that study participants were representative of an obese patient population (mean BMI of 32.8 kg/m2), the majority of which (28 of 31 participants) had some form of abnormal leg alignment on their affected side. As such, the study sample was believed to be representative of a typical knee OA patient population experiencing progressively debilitating joint pain and functional impairment associated with disease progression. That fact that our comparison of baseline and follow-up anthropometric data revealed little change in participant's physical stature was not surprising, as the 12 week exercise regime accounted for only 12 h of exercise over a 12 week period. This level of physical activity is well below exercise recommendations for weight loss. Knee extensor muscle weakness is one of the earliest and most common features associated with OA progression [19,28]. Baseline evaluation of quadriceps muscle strength indicated that scoring was comparable to values previously reported for knee OA patients [15], but also suggested that the thigh muscle strength of our female group was well below normal (it should be noted that the baseline values for the male group were in line with normative values reported in the literature). Follow-up testing indicated that thigh strength improved for all participants, but was only statistically significant for the female group. To our knowledge, this is the first report in which an aerobic activity (in this case — walking) has been successfully used to enhance quadriceps strength in knee OA patients [29,30] (previous reports of strength gains for a knee OA population have primarily involved resistance training programs). This would suggest that the LBPP supported walking exercise intervention had less of an effect on male quadriceps strength as compared to females. Interestingly, the male participants demonstrated greater initial thigh strength, and while they did increase their overall strength, when compared to the female group their strength gains were modest. It is possible that the functional nature of weight bearing exercise supported only small gains in thigh strength, with the law of diminishing returns helping to determine the extent to which a walking program could be used to increase thigh muscle strength (i.e. weaker quads of female participants experienced larger gains in strength as a result of walking). Data regarding acute knee pain during FWB treadmill walking suggest that the LBPP technology warrants much further investigation as a tool that can be used to safely and effectively promote long term exercise adherence in OA patients at significant risk for exacerbation of joint symptoms [5]. Baseline testing revealed that participants experienced substantial acute knee pain during the initial FWB walking session. Following completion of the 12 week walking regime, acute knee pain during the follow-up FWB walking session was significantly reduced, with eight of 31 (or 26%) participants able to walk pain free. Beyond this, a comparison of VAS and LBPP data between the first and last (24th) LBPP supported low-load walking sessions suggested that participants experienced significantly less knee pain while walking during their final LBPP, despite the use of significantly less LBPP support during the walking session. The KOOS questionnaire is widely recognized within the orthopedic literature as being the gold-standard method for assessing short and long-term patient-relevant outcomes associated with OA progression [23]. Baseline KOOS scoring for OA patients recruited to the present study was low (female range 20.0–58.0, male range 35.0–58.0 across all subscales), and well below normal values (ranging from 61.0 to 88.4 across all subscales) previously reported within the literature [31,32]. This is important to note because it places in context the degree of knee pain and level of functional impairment experienced by our participants relative to what would typically be considered normal for a knee OA patient population. Data suggested that our participants experienced significant joint pain and symptoms, as well as great deal of difficulty when performing common activities of daily living (ADLs) such as running, jumping, squatting or going up/down stairs, and were representative of a patient population at significant risk for exacerbation of joint symptoms following regular exercise. Following completion of the 12 week exercise regime, KOOS scoring improved for all participants, and in the case of the female participants, scoring moved more in line with normative values reported in the knee OA literature for three of the five subscales. Interestingly, significant changes in male KOOS scoring were only observed for the Sport/Rec and QOL subscales. This may be reflective of the fact that a greater percentage of the male participants (seven of 9 = 78%) demonstrated a larger amount of articular cartilage degradation (i.e. Kellgren & Lawrence grade III) as compared to the female group, and hence were more susceptible to exacerbation of joint pain and symptoms during normal ADLs. Perhaps the findings of greatest importance to the participants in the study were the COPM results. To our knowledge, this investigation is the first to use the COPM to assess for change in functional performance (and satisfaction with performance) in patients with knee OA. We believe that the COPM data provided a realistic, meaningful, and ecologically valid estimate of each participant's overall functional capacity during activities of daily living that each individual had self-identified as being important and difficult to perform. As such, it provided a patient specific measure of performance and satisfaction with performance when performing self-identified activities of daily living. COPM results from baseline and post-intervention echo the KOOS results, and also provide additional (or supplemental) information on the extent to which participant's normal ADLs were impacted. COPM baseline data suggest that participants felt that their knee OA significantly impaired their ability to perform common leisure activities (such as walking, traveling, gardening, and playing with their grandchildren); adversely impacted their ability to perform activities associated with self-care and independent living (such as going up/down stairs, and getting in/out of the car or tub); as well as diminished their overall work productivity (for example house cleaning, laundry, cooking, and shopping). Beyond this, results indicated that participants were generally dissatisfied with the manner in which their ADLs were affected by their OA knee, Please cite this article as: Peeler J, Ripat J, The effect of low-load exercise on joint pain, function, and activities of daily living in patients with knee osteoarthritis, Knee (2017), https://doi.org/10.1016/j.knee.2017.12.003

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and felt that the disease dramatically limited their ability to perform many common, simple, yet personally meaningful activities of daily living. Following completion of the 12 week exercise regime, COPM data indicated that participants felt that the 12 week exercise intervention enhanced their overall functional capacity, as well as increased their level of satisfaction with how they were able to perform everyday activities that they had self-identified during baseline interviews as being important to them. A strong relationship was also observed between scoring on the performance component of the COPM and the change in scoring observed for the KOOS subscales of pain and joint function. These findings serve to highlight and reinforce participant's perception regarding the effectiveness of the 12 week LBPP supported walking intervention. The KOOS provided a standardized data set that could be used to quantify knee pain and joint function, and facilitated comparison across research settings and populations. The COPM data placed in context the type of activity, and the expectations that participants had during these activities. This data helped to provide relevance, and a deeper understanding of how the 12 week LBPP supported intervention directly affected the lives of each individual participant. It is important to acknowledge that the present study also had several limitations. First, the study design did not utilize a control group. Second, the methodological approach excluded direct examination of knee joint articular cartilage, or pathological biomarkers associated with articular cartilage health. Third, concerns about how a patient's physical perception of LBPP support (i.e., the air pressure) may confound subjective scoring of the pain and function are valid. Forth, because the sample was predominantly female (and large differences in muscle strength were observed between sexes), the results are most generalizable to a female OA patient population. Finally, the question of whether this type of exercise intervention is cost-effective, or superior to other methods of low impact, non-weight bearing exercise warrants further investigation. To our knowledge, there is currently no evidence to suggest that the cost effectiveness of any one form of exercise (i.e., aquatic, cycling, resistance training) is superior to another for the management of symptoms associated with knee OA [2,33–35]. 6. Conclusion The results of this investigation suggest that a 12 week LBPP supported treadmill walking program can be used to help safely and effectively manage joint pain and symptoms associated with normal activities of daily living in patients diagnosed with mild– moderate knee OA. The LBPP walking regimen allowed participants to regularly participate in exercise without exacerbation of joint symptoms. The exercise allowed participants to enhance their strength/weight ratio and diminish their knee pain during activity. KOOS and COPM data both indicated that joint function significantly improved over the duration of the investigation. Further, the COPM data also provided a patient specific measure of performance, and satisfaction with performance, and these scores positively correlated with scoring from pain and activities of daily living subscales on the KOOS questionnaire. Data from this investigation should assist researchers and clinicians to design and implement individualized exercise programs which can be used to safely and effectively manage joint pain and symptoms, as well as optimize the work and leisure productivity of individuals diagnosed with progressive knee OA. Acknowledgments Support for this research was provided by the Manitoba Centre on Aging, the Pan Am Clinic Foundation, and the College of Medicine at the University of Manitoba (125474-340700). The author wishes to acknowledge contributions made to the study design and data collection by Dr. Judit Takacs, Mr. Mathew Christian, and Mr. Steven Piotrowski. Competing interests The author of this manuscript does not have any competing interests with the work described, and thus has no conflict of interest to declare. References [1] Felson DT. Weight and osteoarthritis. Am J Clin Nutr Mar 1996;63(3 Suppl):430S-2S. [2] Jordan KM, Arden NK, Doherty M, Bannwarth B, Bijlsma JW, Dieppe P, et al. EULAR Recommendations 2003: an evidence based approach to the management of knee osteoarthritis: report of a Task Force of the Standing Committee for International Clinical Studies Including Therapeutic Trials (ESCISIT). Ann Rheum Dis Dec 2003;62(12):1145–55. 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Please cite this article as: Peeler J, Ripat J, The effect of low-load exercise on joint pain, function, and activities of daily living in patients with knee osteoarthritis, Knee (2017), https://doi.org/10.1016/j.knee.2017.12.003