Exercise Therapy Recommended to Manage Knee Osteoarthritis

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The benefits of exercise therapy for individuals with knee osteoarthritis (OA) are well known. The ACR strongly recommends both aquatic exercise and land-based aerobic and resistance exercise for managing knee OA.¹

A recent Cochrane systematic review and meta-analysis concluded that high-quality evidence supports the use of exercise to reduce pain and improve physical function and quality of life for those with knee OA.² In fact, the effect sizes for exercise calculated in this meta-analysis are similar to published estimates of the effects of non-steroidal anti-inflammatory drugs.

Recent guidelines from the Centers for Disease Control and Prevention support treating chronic pain (including pain due to OA) with exercise therapy.³

Despite the known short-term benefits of exercise therapy for those with knee OA, maintenance of these benefits is challenging. Studies including sustainability data have noted minimal long-term effects.² This is likely related to the small proportion of patients with OA who meet physical activity recommendations. A 2013 meta-analysis found that individuals with knee OA averaged 50 minutes of moderate to vigorous physical activity per week (measured in bouts of at least 10 minutes).⁴ These averages fall far short of the World Health Organization’s recommendation of 150 minutes per week of moderate physical activity or 75 minutes per week of vigorous physical activity.⁵ A study based on National Health Interview Survey data concluded that nearly half of adults with arthritis do not participate in any form of leisure-time physical activity.⁶

The challenge for rheumatology and rehabilitation clinicians and researchers is to discover the optimal combination of nonpharmacological treatments for knee OA. It’s important to determine what delivery system, mode and dosage of exercise therapies provide the greatest effects for those with knee OA, how best to supplement exercise with manual therapy or other techniques to maximize benefit and how to sustain these benefits over a longer period of time.

Exercise Therapy

Supervised vs. unsupervised exercise: A 2005 study concluded that a clinic-based exercise and manual therapy program was superior to a home-based exercise program after four weeks. Although both groups continued to show clinically meaningful changes at one year compared with baseline, the differential effects between the groups were not maintained at one year.⁷ A recent Cochrane review noted considerable heterogeneity in the number of supervised treatment sessions across studies investigating exercise therapy for knee OA, making it difficult to recommend a specific number of visits or weeks over which to provide formal supervised care.² When comparing home-based and group-based exercise programs to individually supervised programs, the effect sizes for pain were quite different: standardized mean difference (SMD) 0.38 for home-based programs; SMD 0.42 for class-based programs; SMD 0.76 for individually supervised programs.²

Although it may be argued that individually supervised exercise programs are preferable to home- or group-based sessions, the most appropriate number of individually supervised sessions to provide is unclear. Fransen and colleagues found a significant difference between studies providing 12 or more sessions compared to those providing fewer than 12 sessions, but this difference was no longer significant after removing extreme outliers.² Another review noted that exercise interventions are more beneficial when provided at least three times per week.⁸

Mode: Prior studies have included a variety of exercise modes, but most employ treatment programs consisting of both aerobic and resistance exercise. Few studies have directly compared aerobic vs. resistance exercise in knee OA.⁹

A recent pilot trial found that a cognitive-behavioral intervention may be superior to traditional exercise therapy in improving physical activity in sedentary individuals with knee OA over one year.

It’s likely that severity of OA symptoms plays a role in tolerance to certain modes of exercise. Although one study noted no significant difference between weight-bearing and non-weight-bearing lower extremity resistance exercise, weight-bearing exercise may not be well tolerated by some with knee OA due to increased joint loads.¹⁰ However, multi-joint weight-bearing aerobic or resistance exercise may be more functional and can assist in maintenance of bone mineral density. Because current evidence has not yet clearly delineated the optimal mode of exercise for patients with knee OA, exercise prescription should be patient specific, considering the patient’s tolerance for pain-free movement and weight bearing.

Dosage: The proper intensity, frequency and duration of exercise for knee OA have not been determined. Very few studies have actually studied different doses of similar exercises in knee OA. One study found no significant differences between high-intensity and low-intensity quadriceps and hamstring strengthening.¹⁰

Two recent Cochrane reviews concluded that “specific recommendations cannot be made regarding optimal dosage” due to “insufficient evidence to determine the effect of different types of intensity of exercise programs.”^2,11

Another recent article noted the dearth of published trials in which varying prescriptions of intensity and frequency are directly compared in individuals with OA.¹² Clearly, additional research is needed on the topic of optimal dosage of exercise in knee OA.

Because current evidence has not yet clearly delineated the optimal mode of exercise for patients with knee OA, exercise prescription should be patient specific, considering the patient’s tolerance for pain-free movement & weight bearing.

Supplementing Exercise Therapy with Manual Therapy

Manual therapy techniques may include stretching the knee and other lower extremity musculature, mobilization of the tibiofemoral and patellofemoral joints, and soft tissue mobilization techniques. Current ACR clinical guidelines conditionally recommend manual therapy as a supplement to supervised exercise therapy.¹ Several studies directly investigating the effects of manual therapy have been published since the release of the most recent ACR guidelines.

More recent literature: Abbott and colleagues concluded that manual therapy alone provided clinically and statistically significant benefits in pain and physical function over one year compared with usual care in participants with hip and/or knee OA.¹³ However, these authors found an antagonistic interaction between exercise and manual therapy—the combination of manual therapy and exercise therapy resulted in a smaller treatment effect than either manual therapy or exercise therapy alone.¹³ In a later study with a sample of individuals with knee OA, Abbott noted clinically important improvement in pain and function across one year when adding manual therapy with 12 sessions of supervised exercise therapy over nine weeks compared with the exercise therapy program alone.¹⁴

Fitzgerald and colleagues employed an intervention strategy very similar to the 2015 study by Abbott in a larger group of individuals with knee OA.¹⁵ They found a statistically significant benefit to manual therapy after nine weeks of exercise and manual therapy compared to exercise alone, but this benefit was no longer significant at one-year follow-up.¹⁵

A recent laboratory study investigated the effects of knee joint mobilization on deep-tissue hyperalgesia, vibration perception threshold and resting pain levels among individuals with knee OA.¹⁶ They found that knee joint mobilization resulted in increased pressure pain threshold along the medial joint line, improved vibration perception and reduced resting pain.¹⁶ However, these effects were measured only immediately following the application of manual therapy and do not provide information regarding the physiological pain-modulating effects of manual therapy over longer periods of time.

Overall, it appears that manual therapy provides at least short-term benefits in pain and physical function for individuals with knee OA. Although these effects may not be maintained over one year, manual therapy is likely a useful supplement to exercise therapy because it may provide the increased range of motion, accessory mobility, and pain relief necessary for a patient to properly perform the prescribed exercise program.

Sustaining Treatment Effects

Evidence supports the use of exercise therapy and perhaps the use of manual therapy to improve pain, function, and quality of life for individuals with knee OA. However, it appears that these benefits diminish over time.^2,17 Strategies to sustain these positive effects are necessary to promote long-term maintenance of clinical improvements. Recent literature has focused on two ways to promote maintenance of benefits—periodically reinforcing exercise principles through face-to-face visits, and promoting independent management through physical activity promotion and lifestyle changes.

Booster sessions: The current delivery system for rehabilitation services may not adequately promote the maintenance of treatment benefits. Typically, supervised rehabilitation is provided over a short period of time (usually four to eight weeks), and then the patient is discharged to an independent home exercise program with no planned follow-up care with the rehabilitation provider. Booster sessions—periodic follow-up appointments occurring several weeks or months following the initial course of supervised therapy—have been suggested as a way to sustain treatment effects.^7,17,18

The use of booster sessions in physical therapy management of individuals with knee OA is an emerging field of research. Bennell and colleagues found that the addition of two booster sessions to a course of physical therapy did not impact pain, function or adherence to a home exercise program at 24 weeks.¹⁹ However, all participants were provided with an exercise log book to motivate them to continue their home exercise program. It’s possible that the provision of the log book served as a type of booster by reminding patients to continue their exercise program. This may have confounded the results, because it may be argued that both groups received some form of booster.

In contrast, the aforementioned 2015 study by Abbott found that exercise therapy with booster sessions over one year provided greater benefits in self-reported pain and physical function (using the WOMAC) compared with exercise therapy alone.¹⁴ In the larger 2016 study by Fitzgerald, the use of booster sessions did not result in additive improvement in WOMAC scores, but secondary analyses showed that use of booster sessions improved knee pain and odds of being a responder at one year (substantial patient-rated improvement using OARSI-OMERACT responder criteria).^15,20 Taken together, these studies suggest using booster sessions may be a promising way to sustain treatment effects over time; however, further research is necessary to clarify the role of booster sessions in sustaining positive effects of exercise and manual therapy for individuals with knee OA.

Physical activity promotion: Optimal self-management of knee OA requires a commitment to regular physical activity. However, the best method for encouraging those with OA to meet physical activity recommendations is not clear. A recent review of physical activity programs for overweight individuals with OA noted that, “evidence for long-term maintenance of physical activity behaviors is limited and needs further investigation.”⁹ Among articles included in that review, most did not find a benefit to various self-management or walking promotion programs.^21-23

Pisters compared a “behavioral graded activity” program with standard physical therapy for individuals with hip or knee OA.²⁴ The behavioral graded activity intervention slowly increases the dose of physical activity over time and uses principles of operant conditioning and self-regulation to promote a more physically active lifestyle. They found that the behavioral graded activity program significantly increased the odds of adhering to the prescribed exercises (OR 3.0, 95% CI 1.5–6.0) and meeting physical activity recommendations (OR 2.9, 95% CI 1.2–6.7) at 65 weeks.²⁴ In this study, only the individuals receiving behavioral graded activity intervention received booster sessions. Therefore, it is not possible to state whether the benefits for the experimental group are due to differences in the components of the two interventions, differences in the time over which the face-to-face interventions were delivered or a combination of both.

A recent pilot trial found that a cognitive-behavioral intervention may be superior to traditional exercise therapy in improving physical activity in sedentary individuals with knee OA over one year.²⁵ The group receiving the cognitive-behavioral intervention participated in sessions over the course of nine months, and the traditional center-based supervised exercise therapy received three visits per week for three months.²⁵ Because of the differences in timing of face-to-face treatment sessions, it’s again difficult to ascertain whether the differences in effects were due to the nature of the intervention itself or the timing of its delivery.

Another recent study employed a novel Internet-based physical activity promotion program for individuals with knee and/or hip OA.²⁶ Self-reported physical activity was higher after 12 months for the intervention group compared with the waiting control group. Such a program is an intriguing option, because it does not require in-person visits to complete and, thus, may be substantially more accessible and less expensive than alternatives. However, the results of this study should be interpreted with caution due to high rates of nonadherence and dropouts.

Conclusion

Although a variety of rehabilitation strategies involving exercise have been effective at improving pain, function and quality of life for individuals with knee OA, further research is necessary to determine the optimal mode, dosage and level of supervision required for exercise therapy.

In addition, manual therapy, booster sessions and physical activity promotion programs should continue to be studied to further illuminate their potential roles in providing and maintaining treatment effects over time.

Allyn M. Bove, PT, DPT, is an assistant professor in the Department of Physical Therapy at the University of Pittsburgh School of Health and Rehabilitation Sciences. She received B.S. degrees in Biology and Health Sciences from Duquesne University in Pittsburgh and a Doctor of Physical Therapy degree from Columbia University in New York, and is currently completing PhD studies at the University of Pittsburgh. Her research interests include racial disparities related to knee OA, total knee arthroplasty and cost effectiveness of non-surgical treatments for knee OA.

G. Kelley Fitzgerald, PT, PhD, FAPTA, is professor and associate dean of graduate studies at the University of Pittsburgh School of Health and Rehabilitation Sciences and serves as director of the Physical Therapy Clinical and Translational Research Center. He has earned degrees from the University of Illinois, Chicago Medical School, Virginia Commonwealth University, and the Medical College of Pennsylvania/Hahnemann University. He has more than 26 years of experience as a physical therapy clinical researcher and focuses his research on knee OA.

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