Although the medical literature has not yet provided definitive evidence of effectiveness, a number of existing studies suggest that yoga interventions are associated with improved physical and mental health outcomes among adults with knee osteoarthritis.
By Monica R. Maly, PT, PhD
One in every six Canadians will experience arthritis—nearly six million by 2026.1 By 2031, more than two million Canadians aged 45 to 64 years will have arthritis, and of these, one in three will be out of work.2 Even more concerning is the chronic pain caused by arthritis, which results in immobility and dependence on others.2
The most frequent form of arthritis is osteoarthritis (OA), a complex chronic condition that degrades all tissues inside and around a synovial joint. The number of Canadians with OA will nearly double between 2010 and 2031; as a result, the total Canadian healthcare costs associated with treating these individuals will rise from CA$1.8 billion to CA$8.1 billion.3 It most commonly affects weightbearing joints, such as the knee, which endure large loads associated with daily activity. Knee OA is the single greatest cause of chronic disability among community-dwelling older adults.4
Knee OA compromises quality of life by challenging both physical and mental health. It causes chronic pain and limits performance of tasks such as walking, stair climbing, and rising from a chair. Although these physical consequences of knee OA are well known, this disease also has a tremendous impact on mental health. The mobility limitations associated with knee OA foster social isolation.5 It is not surprising, then, that people with knee OA are more likely than their healthy counterparts to experience depression, anxiety, insomnia, helplessness, and poor self-efficacy (confidence in the ability to complete a task).2,6 Depression is strongly associated with poor perceptions of physical function,7-11 and low self-efficacy12,13 negatively influences mobility.14-16 Importantly, these psychosocial issues are also associated with elevated pain and worsening knee OA over time.6 Clearly, mental health must become an overt target in the management of knee OA.
Knee OA management
Currently, clinical practice guidelines for knee OA largely ignore the strong influence of mental health comorbidities on quality of life. Mainstay treatments for knee OA include pharmacology for pain relief and, ultimately, a surgical intervention such as total joint replacement. Clinical practice guidelines also highlight exercise as fundamental in the care pathway for knee OA.17-19 Strengthening exercise in particular is a cornerstone of conservative knee OA treatment.20-24
A 2015 Cochrane review emphasized that high-quality evidence supports the use of land-based exercise to reduce pain, and moderate-quality evidence supports the use of exercise to improve physical function.25 In fact, high-quality evidence showed that strengthening, even at a low intensity, improves knee extensor and flexor strength in patients with knee OA.26 The standardized effect sizes associated with the use of exercise to improve pain and physical function were .40 and .37, respectively—equivalent to improvements associated with pain medications.22
Little is known about how to effectively improve mental health in patients with knee OA.18 It is likely that exercise has a positive impact on mental health conditions such as depression and self-efficacy in people with knee OA, but relatively few studies demonstrate this effect. Some evidence points to exercise as useful in improving psychological outcomes. For example, in 199 participants with hip or knee OA, a nine-week web-based intervention that aimed to gradually increase physical activity improved tiredness and anxiety, even at the 12-month follow-up.27 Interestingly, pain coping also improved, suggesting one mechanism by which exercise can improve mental health in people with knee OA. This ability to boost self-care is at the core of self-management programs that integrate education about arthritis, exercise, and pain management for people with knee OA.28-31
Recently, self-care for knee OA has been enhanced further with cognitive-behavioral techniques (CBT). CBT for chronic pain includes three components: education about pain and the role of pain-coping skills, training in coping skills, and applying coping skills to real-life situations. In a feasibility randomized controlled trial, 20 participants with knee OA were randomized to receive either exercise and pain-coping skills training or exercise and nondirective counseling for 10 weeks.32 Both groups reported improvement in pain; however, no differences in this pain outcome existed between groups at follow-up. This trial was too small to form conclusions about effectiveness; it is possible that combining exercise with CBT will improve quality of life to a greater extent than exercise alone for people with knee OA. However, the CBT approach requires access to two professionals (or one professional with additional specialized training), increasing the burden of time and resources, at least in the short term, to improve health.
Yoga: a mind-body intervention
From a Western perspective, yoga is a complementary alternative medicine that directly addresses physical and mental health. However, a traditional view shows that yoga is one component of a holistic lifestyle—yoga means “union” and suggests a lifelong practice devoted to achieving harmony with self, society, and nature. It includes practices of self-restraint, physical exercise, breathing, deep relaxation, and meditation.33 No mainstream research has investigated the impact of this holistic yogic lifestyle on quality of life, or health outcomes, in people with OA. It is exciting to note that the results of a clinical trial tackling the challenges of studying this traditional approach to yoga should soon be available at clinicaltrials.gov.34
Meanwhile, studies that focus on the physical exercise, meditation, and breathing elements of yoga—a Westernized approach—are available. These studies show that yoga has promise as a management strategy: It improves strength, balance, flexibility, pain, and disability in older adults.35-40 The evidence supporting the effectiveness of yoga in people with knee OA, however, is less certain.
Several small studies show yoga improves both physical and mental health outcomes in patients with knee OA. For example, a pilot study enrolled seven women older than 50 years with symptomatic knee OA in an eight-week program of modified yoga postures.39 Each week, participants attended one 90-minute class. Participants reported improvements in knee pain, self-reported physical function, and affect (expressed emotional responses); however, walking performance remained unchanged.39 In a different study, after seven yoga classes, the number of nights with insomnia (self-reported) was significantly improved in 13 women with OA in any joint.41 A case series of 14 people with symptomatic knee OA also showed yoga was associated with improved quality of life.35
Although these early studies point to the potential for improvement in physical and mental health after yoga, it is important to note that the improvements were limited to self-reported measures, and the exposure to yoga was relatively short and infrequent.
Because self-reported function and actual performance are not well-correlated,42 it is important for research to include both types of measurements. Recently, we conducted a simple yoga trial in 38 women with symptomatic knee OA who completed 12 weeks of supervised yoga-based strengthening exercise three times a week.43 A unique element of our yoga program is that we selected yoga postures (eg, lunges, squats, stretches) that would minimize patients’ exposures to knee joint loads known to worsen structural disease in the knee.43 Our “biomechanical” yoga program (see Figure 1, below) improved pain, self-reported physical function, objective measures of mobility performance (eg, walking speed), and knee extensor and flexor strength. However, we observed no changes in physical fitness or knee mechanics during walking and yoga postures or in muscle activation after the yoga intervention.44
These findings show yoga can improve muscle strength in women with knee OA, which translates to improved mobility. Nonetheless, it is important to note that, in all of these early studies, including ours, the small samples and lack of comparison with a control group means we cannot be sure if enrollment in the study itself (that is, the attention and the researchers’ intention to address each patient’s chronic knee problems) is responsible for the improvements, rather than the yoga intervention.
A handful of studies have compared outcomes after a yoga intervention with those of a control group. For example, an eight-week randomized controlled trial of sedentary people with both rheumatoid arthritis and OA showed that yoga was associated with more improvement in walking performance, depressive symptoms, and perceived physical health compared with a waitlist control group.45 Although this trial had greater-than-ideal losses to follow-up (24%), no adverse events were related to yoga. Similar findings were reported for a sample of women with knee OA.46
Older adults living in a senior center had greater improvement in depressive symptoms and life satisfaction after a sitting yoga program (n = 23) compared with a control group who received education but no exercise (n = 11).47 However, pain, walking performance, and balance performance were unchanged, suggesting this intervention improved psychological but not physical status.
It is important to note that, while the study design called for concealed allocation, the nature of this trial required that we exclude 26% (n = 9) of individuals from randomization because of limited cognition, placing them into the siting yoga group. Nevertheless, though not a true randomized controlled trial, this study showed that older adults who cannot participate in standing exercise due to weakness, balance impairment, or pain could benefit from a sitting yoga class.47
Two studies have investigated whether adding yoga to traditional treatment for people with knee OA provides greater benefit than traditional treatment alone. In a nonrandomized trial of patients who had undergone knee replacement (n = 51), a combined program of yoga and physical therapy was associated with greater improvement in WOMAC (Western Ontario and McMasters Universities Osteoarthritis Index) pain and stiffness scores than physical therapy alone.48 However, adherence to the home-based exercise in either group was not reported, making it unclear if the participants actually completed the requested exercises once home from the hospital.48
A large randomized controlled trial of 250 men and women aged between 35 and 80 years with knee OA implemented two study arms: traditional physical therapy for two weeks (exercise, transcutaneous muscle stimulation, and ultrasound) versus traditional physical therapy and yoga for two weeks. Adding yoga to supervised physiotherapy improved overall health-related quality of life, anxiety, morning stiffness, blood pressure, and pulse rate more than physiotherapy alone.49-51 No information was given, however, about adverse events, or the number of participants who completed the study.
It is possible that the patients who received yoga in addition to standard care showed greater improvement simply because they received more treatment. It is also worth noting these randomized controlled trials involved relatively small volumes of yoga, below the typical standard of exercise (three times per week for 12 weeks)52 considered necessary to induce changes in the musculoskeletal system.
Only one study has compared the impact of yoga-based exercise with another treatment regime.53 A three-armed pilot study randomized participants to a chair yoga program and a Reiki program and included a control (education) group. Results showed improvements in self-reported physical function in older adults with OA are greater after a chair yoga program (45 minutes twice a week for eight weeks) than after a Reiki program (30 minutes once a week for eight weeks). Although this comparison is interesting and encouraging, the comparison of yoga to a treatment (Reiki) that is not established in Western literature as effective limits the strength of the findings. A comparison of yoga to a traditional treatment that has been clearly demonstrated to be effective in patients with knee OA, such as strengthening exercise,25 is warranted.
Limitations of the literature
Ultimately, while existing studies provide some encouragement that yoga has promise as a mind-body approach to knee OA, there are not enough high-quality data to prove effectiveness. Several limitations of the existing work mean we cannot be sure that yoga is an ideal, or effective, approach to treating the physical and mental health problems created by knee OA.
First, the majority of the available studies are limited by small samples, uncontrolled designs, and limitations in reporting important details, such as how many participants completed the intervention. These limitations result in bias toward favorable results; any improvements may have more to do with the attention participants receive than the intervention itself.
Second, existing studies of yoga for knee OA have focused on self-reported measures. These measures are essential for providing an individual’s perspective on mental health, pain, and quality of life. However, objective measures (for example, mobility performance or blood pressure) are necessary to capture the extent to which physical and mental health improvements can be observed. Further, a focus on mental health measures directly relevant to issues in knee OA, such as depressive symptoms and anxiety, would be of great benefit.
Third, there is little consistency between studies with regard to the yoga protocols used, making it challenging to develop recommendations for people with knee OA.54 The frequency, duration, supervision, and type of yoga must be clearly defined and should be consistent with recommendations for any exercise intervention for knee OA.52
Adverse events have been reported rarely in trials exploring the efficacy of yoga exercise in people with knee OA. As a result, the safety of yoga as an intervention for knee OA may be unclear, particularly with respect to concerns that the intervention’s emphasis on range of motion may exceed the tolerance of tissues inside an osteoarthritic joint.45 With this reporting limitation in mind, serious adverse events (that is, events that require hospitalization) were not noted in any study.
Some evidence suggests that musculoskeletal pain associated with sprains and strains in the low back, wrist, ankle, knee, or Achilles tendon may occur as a result of a yoga intervention.44,55 In the interest of safety, extreme ranges of motion that may be practiced in advanced or specialized yoga approaches are unlikely to be appropriate for older adults. Further, specific comorbidities in older adults require attention; for example, postures challenging single-leg standing balance that could result in a fall likely have significant potential for harm in those with osteoporosis.
The bottom line
Individuals with musculoskeletal problems, such as those with knee OA, are frequent users of complementary therapies and alternative medicine.56 The popularity of yoga as an exercise intervention provides an additional venue through which we as clinicians can promote physical activity among people with knee OA. Although the existing data do not provide definitive evidence of effectiveness, the studies are reasonably consistent in demonstrating improvement in physical and mental health outcomes among adults with knee OA. Providing more choices for physical activity, such as yoga, will hopefully improve exposure and adherence.
The Westernized approach to yoga, focusing on physical exercise, breathing, and meditation, appears reasonably safe; no serious adverse events have been reported in the literature to date. The main risk associated with engaging in yoga would be that future trials could reveal yoga is ineffective. However, while we wait for randomized controlled trials to provide higher-quality evidence, it appears likely that yoga is an excellent addition to a conservative treatment program for older adults with knee OA.
It makes sense to ensure that people with knee OA are completing time-tested interventions, such as traditional strengthening exercise. The addition of yoga is likely to be useful in further boosting physical and mental health in people with knee OA.
Monica Maly, PT, PhD, is associate professor in the School of Rehabilitation Science at McMaster University in Hamilton, Ontario, Canada. She is a physiotherapist and biomechanist who holds a New Investigator Award from the Canadian Institutes of Health Research.
Disclosure: The author gratefully acknowledges funding support from the Natural Sciences and Engineering Research Council of Canada and the Labarge Optimal Aging Initiative.
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