May 2010

Yoga practice enhances management of knee OA

Figure 1. Poses like Virabhadrasana (Reverse Warrior) and Virabhadrasana 2 (Warrior 2) help strengthen the quadriceps. (Photos courtesy of Breathe Joy Yoga Photos by Cindy Greenstein.)

Research suggests that a tailored yoga practice can help reduce pain and improve function in patients with knee osteoarthritis. Potential mechanisms include strengthening, improving flexibility, and altering gait biomechanics.

by Richa Mishra, MD, and Sharon L. Kolasinski, MD

Osteoarthritis (OA) is a chronic disease of cartilage and surrounding tissues characterized by biochemical and morphologic alterations in the synovial membrane and joint capsule, erosion of the articular cartilage, bony hypertrophy, and subchondral sclerosis. It is the most common form of arthritis, affecting more than half of adults over the age of 651,2 and resulting in well over a half-million total joint replacement surgeries annually.3

OA is a leading cause of physical disability, increasing healthcare utilization, and impaired quality of life in developed nations.4 Women are twice as likely as men to develop symptomatic OA. Although women have a lower prevalence of OA than men before age 50, there is a marked increase in prevalence among women over 50, particularly in the hands and knees.5

Studies have shown that mechanical actions in the joint have physiologic effects at the cellular level.6-8 Chondrocytes, cells within the cartilage that produce components of the extracellular matrix but fail to function properly during the pathogenesis of OA, can sense and respond to mechanical and physiochemical stimuli via several regulatory pathways. It is well known that exercise can have a positive impact on osteoarthritis symptoms and associated disability.9,10 However, it can be difficult for these patients to begin and continue exercise programs. Yoga offers an additional approach to the incorporation of exercise into the management strategy for patients with osteoarthritis, and a number of studies have begun to provide evidence to support its use.

What is yoga?

Yoga is an ancient practice that aims to create a harmonious balance between mind and body. The Sanskrit word from which the term “yoga” is derived is “yuj,” meaning to yoke or unite. Yoga is thought to permit a union of mind, body, and spirit. By combining mental and physical fitness, yoga may reduce stress, strengthen the body, and increase flexibility. The holistic perspective from which yoga derives seeks to develop self-awareness, emotional stability, and peace of mind.

The practice of yoga was initially developed around 150 BC by Patanjali in ancient India, and it has evolved over time. Yoga has six traditional branches of which hatha yoga, or “the yoga of posture,” is the most well known in Western nations. This branch of yoga uses physical poses, or asanas; breathing techniques, or pranayama; and meditation to achieve improved health and spirituality. There are many styles within this path of which Iyengar yoga has become particularly popular in the U.S. Iyengar yoga is characterized by its precise focus on body alignment. It uses aids like cushions, benches, blocks, and straps to help practitioners achieve asanas more easily, more fully, and with less muscular effort than might otherwise be possible if unaided. Standing poses emphasized in Iyengar yoga are said to build strong legs; increase general vitality; and improve circulation, coordination, and balance.11

Potential mechanisms of action

Figure 1. Poses like Virabhadrasana (Reverse Warrior) and Virabhadrasana 2 (Warrior 2) help strengthen the quadriceps. (Photos courtesy of Breathe Joy Yoga Photos by Cindy Greenstein.)

Although yoga was introduced in the U.S. in the late 1800s, medical literature about the physiologic effects of yoga remains relatively scarce. Yoga to reduce symptoms in the knee may include specific asanas that strengthen the quadriceps and other muscles that can help relieve physical stress on the knee joint. The statics and movements of yoga could theoretically have a positive effect in those with OA via this strengthening. Postures that might achieve this include Virabhadrasana (Figure 1) and Supta Tadasana (Figure 2).

Different postures might focus on flexibility and increased blood flow, presumably by aligning joints, including the ankles, knees, and hips. Standing postures could strengthen and align bones and muscles, particularly of the lower extremities. Stretching can be achieved by bending and twisting. Traction and active alignment from the use of one’s own muscles, if tolerated, might be preferable to passive traction by the use of external postures. Inverted postures may rest the legs and could help nervous system function.12

Further, the cellular effects of mechanical and fluid pressure on structures such as cartilage suggest that yoga postures might alter joint function. Low levels of intermittent fluid pressure, as occur during joint distraction, have been shown in vitro to decrease production of catabolic cytokines, such as interleukin-1 and tumor necrosis factor-α.7 In experimental settings, joint motion preserves cartilage that can be lost by immobilization.8 Correctly supervised yoga may be one way to provide the motion and forces on joints needed to preserve integrity.

Indirect evidence for these hypotheses comes from studies regarding the effects of active and passive exercise in a supervised or home setting. Deyle et al found that a combination of manual physical therapy and supervised exercise yielded superior functional benefits for patients with osteoarthritis of the knee compared to placebo and could delay or prevent surgical intervention.13 In this randomized, controlled clinical trial, 83 subjects with osteoarthritis of the knee were included. The treatment group received manual therapy applied to the knee, as well as to the lumbar spine, hip, and ankle as required, and performed a standardized knee exercise program in the clinic and at home. Exercises were taught by experienced physical therapists with formal training in manual therapy. The placebo group had subtherapeutic ultrasound to the knee. Both groups were treated at the clinic twice weekly for four weeks.

Clinically and statistically significant improvements in six-minute walk distance and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score (primary endpoints) were noted at four weeks and eight weeks in the treatment group but not the placebo group. By eight weeks, average six-minute walk distances had improved by 13.1% and WOMAC scores had improved by 55.8% over baseline values in the treatment group (p = 0.05). At one year, 20% of patients in the placebo group and 5% of patients in the treatment group had undergone knee arthroplasty.

Deyle and colleagues went on to study the effectiveness of manual physical therapy and exercise in OA of the knee compared to a home exercise program alone.14 They found that the home exercise program not only reduced symptoms after eight weeks, but that those benefits could be sustained by continued exercise at one year. Furthermore, the addition of manual therapy enhanced the symptom relief. The implication for interventions such as yoga could be that additional supervision and attention to alignment and stretching might enhance the therapeutic results of exercise alone.

Yoga may also benefit those with knee OA via quadriceps strengthening and general stretching. Quadriceps strengthening has long been noted to be of importance in the development of knee osteoarthritis, and there is ample evidence that muscle-strengthening exercises improve pain reduction, physical function, and quality of life in people who have knee OA.15-18 Several yoga asanas used in the treatment of OA of the knee, such as Uttitha Trikonasana (Figure 3) and Dandasana (Figure 4), which emphasize fully extending the knee, can strengthen the quadriceps. Similarly, other work has suggested that when stretching is added to isokinetic exercise, not only can pain and disability be reduced, but muscle strength and range of motion can be improved.19 Asanas using straps, such as Supta Padangustasana (Figure 5), emphasize stretching and, thus, may be of particular benefit in treating OA.

Clinical trials

Figure 2. Poses like Supta Tadasana (Reclined Mountain Pose) take stress off the knee. (Photo courtesy of Elsie's Yoga Kula

One of the earliest studies to suggest that yoga might be a useful intervention for those with osteoarthritis evaluated the effectiveness of a regimen for hand OA.20 In this small trial, 24 patients with OA of the hands were randomly assigned to a yoga program or no therapy. Yoga techniques were supervised by one instructor once a week for eight weeks. The yoga treatment group improved significantly more than the control group with regard to pain during activity, tenderness, and finger range of motion.

Subsequently, several studies suggested that yoga might be helpful for those with osteoarthritis in the lower extremities. A pilot study by Kolasinski and colleagues concluded that Iyengar yoga may offer a feasible treatment option for previously yoga-naive, obese patients and can reduce pain and disability caused by knee OA.21 In this trial, 11 subjects meeting American College of Rheumatology criteria for knee OA were enrolled. Subjects were instructed in modified Iyengar yoga postures during 90-minute classes once weekly for eight weeks. No home exercise program was required. Nine people completed at least one session, the average number of sessions completed was five, and seven (six of whom were obese) had data from pre- and postcourse time points available for analysis. At the end of the study, statistically significant reductions in WOMAC Pain, WOMAC Physical Function, and Arthritis Impact Measurement Scale 2 (AIMS 2) scores compared to their pre-intervention status were seen. Physician Global Assessment (MDGA) and Patient Global Assessment (PGA) also showed trends in improvement. No adverse events from treatment were reported.

Figure 3. Standing poses like Utthita Trikonasana (Extended Triangle) emphasize fully extending the knee. (Photo courtesy of Breathe Joy Yoga Photo by Cindy Greenstein.)

A study by Bukowski and colleagues also looked at the effect of Iyengar yoga and strengthening exercises in subjects with knee OA.22 Fifteen participants were assigned to a traditional stretching and strengthening regimen, Iyengar yoga, or no exercise. Low back and hamstring flexibility and quadriceps strength and function were monitored before and after the program. The WOMAC Osteoarthritis Index and a global assessment questionnaire were also used to assess improvement. After the six-week intervention period, functional changes and improvement in quality of life were noted in the traditional exercise and yoga groups compared to the controls. Those with the greatest improvements in flexibility and quadriceps strength had the greatest improvement in WOMAC scores.

Two subsequent studies have suggested that at least part of the effect of yoga on subjects with knee OA involves alteration of gait. Evangelisto and colleagues looked at biomechanical changes following an eight-week yoga intervention in the knee as assessed by formal gait laboratory analysis.23 WOMAC pain, stiffness, and disability and visual analog scale (VAS) scores were used to assess the improvement. All subjects met ACR criteria for knee OA. They participated in eight weekly 90-minute Iyengar yoga classes. Three-D motion analysis revealed a statistically significant reduction in ankle dorsiflexion, an increase in plantar flexion, and an increase in the total range of motion for pelvic tilt between baseline and follow-up evaluations. Analysis of footfall parameters from baseline to follow-up revealed significant increases in walking speed as well as maximum moments during hip rotation, hip flexion/extension, and knee varus. Three of four subjects who completed seven of eight yoga classes had reductions in WOMAC pain, stiffness, and disability. The increased walking speed and modified ankle motion during gait may underlie the improvements in WOMAC scores. Thus, improved biomechanics may lead to a reduction in symptoms.

A second study used gait analysis to elucidate the potential role of Iyengar yoga in treating elderly patients with impairments in ambulation.24 Participants were nonobese, yoga-naive subjects older than age 62 who did not require assistive devices. Nineteen individuals completed the eight-week study, which included two 90-minute Iyengar hatha yoga classes each week, as well as a minimum of 20 minutes of home yoga practice five times a week. Relative to baseline values, both peak hip extension and stride length at comfortable walking speed demonstrated significant increases after the intervention. The researchers also observed a trend toward a decline in average pelvic tilt from baseline to eight weeks. Change in peak hip extension was strongly and positively related to change in ankle plantar flexion and ankle joint power. Stride length was strongly and positively related to all three secondary outcome measures, including walking speed.

Figure 4. Dandasana (Staff Pose) is another pose that emphasizes fully extending the knee. ( #8016322)

Importantly, the frequency of yoga practice at home (measured in total days and mean days per week) and the duration of practice (measured as mean minutes per day) showed a strong linear dose-response relationship to change in hip extension and average pelvic tilt. The authors noted that loss of hip extension and the compensatory increase in pelvic tilt and reduction in stride length is associated with aging, the risk of recurrent falls, and increased morbidity and mortality. Both of the studies using gait analysis to evaluate patients with knee OA who did yoga suggest that altering gait biomechanics is not only possible via yoga but that it can be associated with improvements in pain and other outcomes as well.

Another study has also suggested that yoga might be used to prevent falls in the elderly.25 A total of 27 subjects over age 65 participated in a program of weekly 45-minute yoga sessions without the aid of props or assistive devices and excluding floor exercises. At three-month follow-up, beneficial effects on balance were demonstrated using a number of outcome measures. The authors suggested that future studies of fall prevention using a yoga intervention would be appropriate. Osteoarthritis is among the factors that may contribute to an unsteady gait in the elderly, and improvement in symptoms due to OA may account for some of the improvement noted in this trial.

A final recent trial looked at the effectiveness of Iyengar yoga for chronic low back pain.26 In this study, 90 patients receiving standard medical therapy were randomized to a yoga group (n = 43) or a control group (n = 47). Yoga subjects participated in 24 weeks of biweekly yoga classes designed for chronic lower back pain. Outcomes were assessed using the Oswestry Disability Questionnaire, a VAS, the Beck Depression Inventory, and a pain medication-usage questionnaire.

There were significant reductions in functional disability and pain intensity in the yoga group compared to the control group at 24 weeks. A significantly greater proportion of yoga subjects also reported clinical improvements at both 12 and 24 weeks. In addition, the mean depression score on the Beck Inventory was significantly lower (indicating less severity) in yoga subjects at both 12 and 24 weeks. When results were analyzed using per-protocol analysis, improvements were observed for all outcomes in the yoga group, including a greater trend for reduced pain medication usage. The yoga group had statistically significant reductions in functional disability, pain intensity, and depression compared to standard medical care at six months postintervention. This study concluded that yoga improves functional disability, pain intensity, and depression in adults with chronic lower back pain. A clinically important trend for the yoga group to reduce their pain medication usage compared to the control group was also reported. These observations have potentially important implications for any patient with a source of pain that requires treatment with medication, characteristics shared by those with back pain as well as knee osteoarthritis. Furthermore, depression is known to affect symptoms of OA.27,28

Potential adverse effects

Figure 5. Beginners may not be able to perform Utthita Hasta Padangusthasana (Standing Extended-leg Stretch, shown), but a supine version (Supta Padangusthasana) can be performed using a strap if needed. (Photo courtesy of Breathe Joy Yoga Photo by Robyn Parets.)

Studies involving yoga have included protocols that were specifically designed by experienced practitioners to address particular health issues and performed under close supervision. They have generally excluded subjects with significant inflammatory arthritis or previous joint replacements, as well as those with a significant history of nonmusculoskeletal medical problems. Thus, conclusions about the use of yoga as an intervention for specific diseases remain limited.

In making recommendations for patients about the appropriateness of yoga as a therapeutic option, healthcare providers should be aware of the limitations of current data. Furthermore, it is reasonable to advise patients to discuss their medical limitations with a yoga instructor before embarking on a yoga exercise regimen. However, virtually no adverse effects have been reported to results during yoga clinical trials, and there have been only rare reports of adverse events associated with the practice of yoga.

A 34-year-old man was found to have rupture of the lateral collateral ligament after presenting with acute knee pain following yoga practice.29 During his practice, the patient had performed a posture that required flexion and varus movement of the left knee while putting the left foot over and behind the head. He felt discomfort and minor swelling around the lateral aspect of his knee after hearing a “pop” during the posture. He was subsequently able to bear weight and participate in activities of daily living, but varus strain produced localized knee discomfort. Physical examination showed normal gait, normal alignment, and no effusion but mild focal tenderness over the fibular collateral ligament near the insertion of the fibula and grade II laxity of the lateral collateral ligament with varus force in 30° of flexion. Plain radiographs were normal, but an MRI revealed a bruise of the medial tibial plateau and an avulsion of the fibular collateral ligament at its distal attachment. The patient recovered functionally with no intervention, though at one-year follow-up, he had grade I residual laxity.

Another case report documented bilateral sciatic nerve palsy, confirmed electrodiagnostically, in a 42-year-old woman who fell asleep for four hours in a seated posture with her torso bent forward and legs fully extended.30 The therapeutic use of oxycodone and amitriptyline contributed to her somnolence. Two additional case reports discussed ophthalmologic complications of yoga practice. A 46-year-old woman with a 20-year history of open-angle glaucoma developed a partially reversible visual field defect after she began a headstand position during her yoga practice.31 A 62-year-old yoga instructor was reported to develop intermittent painless proptosis without associated visual change with forward bending. MRI showed that this was related to enlargement of an orbital varix in a forward bent position.32


Yoga is an ancient and complex practice, one aspect of which involves physical exercise that is believed to have a variety of benefits. The demonstrated benefits of yoga include pain reduction and improvements in joint range of motion and function. Should yoga be suggested for symptom control in patients with osteoarthritis or other musculoskeletal concerns, the goals of therapy should be made clear to the patient. Yoga practice as a therapeutic intervention should be medically supervised in the same manner as any other exercise program.

Common sense precautions for those with musculoskeletal complaints include not performing postures beyond the limits of comfort and avoiding excessive repetitions. Patients should be encouraged to inform their yoga instructors of their medical history prior to the start of the class and to point out any difficulty they may have in assuming asanas during class. Based on the currently available evidence, yoga can provide an appropriate exercise option for those suffering from aches and pains due to osteoarthritis.

Richa Mishra, MD, is a rheumatology fellow at the University of Pennsylvania. Sharon Kolasinski, MD, is professor of clinical medicine at the University of Pennsylvania School of Medicine, interim director of the division of rheumatology, and rheumatology fellowship program director.


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