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Jun14
  • OBJECTIVE To determine whether physical exercise constitutes a benefit or a risk in the development and progression of knee osteoarthritis
  • QUALITY OF EVIDENCE- For individuals without osteoarthritis, strong level II evidence was found (limited by problems with blinding and randomization); for those with pre-existing knee osteoarthritis, robust level I evidence was available.
  • MAIN MESSAGE Knee osteoarthritis is a major contributor to disability in seniors, and patients have expressed concern that continued exercise might lead to knee symptoms in later years. Studies done on subjects self-selected for exercise and followed for substantial periods of time show no evidence of accelerated development of osteoarthritis, provided injury is avoided. Further, there is good evidence for reduced pain and disability with exercise in this cohort compared with controls. Patients with established osteoarthritis are shown to derive uniform benefit to physical functioning, with reduction of pain and disability, using aerobic, muscle strengthening, aquatic, or physiotherapy-based exercise modalities.
  • CONCLUSION Provided trauma is avoided, moderate exercise does not lead to acceleration of knee osteoarthritis, whether or not there is evidence of pre-existing disease. In either case there appears to be improved physical functioning and reduction of pain and disability in those who exercise. It is likely that exercise interventions are underused in the management of established knee osteoarthritis symptoms.
  • Knee osteoarthritis (OA) is seen radiographically in 33% of the population older than 60 years of age,1 and is responsible for a higher incidence of disability than any other chronic condition. It is as potent a factor as cardiovascular disease in limiting activities of daily living in the elderly.2 At the same time, seniors, because of advances in disease management, are living longer with the potentially increased burden of chronic diseases, which would otherwise limit lifespan. Any intervention that can improve physical function and minimize the limitations imposed by knee OA in seniors will add quality to the years spent in the latter part of life.
  • Predictors of mortality tend to gradually change with age. Factors such as socioeconomic status, smoking, and obesity become progressively less influential at the upper extremes of age when physical performance, level of disability, and cognitive performance emerge as the most important determinants.3 There is evidence that nonagenarians do not live with a higher degree of disability than their younger peers.4 Their illness events are often delayed until shortly before death and often span a shorter period of time.5 The first major illness is usually, then, a terminal one. Therefore, maintenance of physical activity and prevention of premature disability are increasingly important for life satisfaction with longevity. It is important to understand the role of exercise in the etiology and natural history of knee OA, one of the most prevalent conditions leading to disability in old age.  
  • What is the role of exercise in causing knee OA?

  • A 60-year-old man has been running 30 km/wk for 35 years. He has no history of noteworthy illness and has never had a sports- or running-related injury. He has been told that he is wearing out his knees and that he will get arthritis if he continues to run, but he wishes to remain active as he gets older. He asks your advice.

  • Evidence for the influence of exercise on knee OA onset is all level II, owing to problems with compliance and blinding in imposing this type of intervention. Studies are observational and are done on self-selected populations. There is no externally imposed intervention. These studies do, however, provide an opportunity to evaluate quite vigorous levels of exercise, and many of them are of prospective cohorts followed for very long periods of time.
  • While presence of knee OA is often the end point in these studies, there is generally a poor correlation between x-ray findings and symptoms. A diagnosis of knee OA is really only a surrogate for lower extremity pain and disability, which are major components of reduced quality of life in seniors. The process advances with age equally in those who exercise and those who do not.28 The best prospective cohort studies12,2935 show no increase in rate of progression of knee OA in individuals who exercise compared with those who do not. Many of these populations are followed for long periods of time. Only one cohort study17 shows increased OA in individuals who exercise, and only in those with a history of “heavy physical activity.” More important, there is convincing evidence—as well as lack of dissenting opinion—that increased levels of exercise lower the incidence of musculoskeletal disability, reduce pain, and increase functional capacity.28,31,37 In fact, Stanford University’s runners’ study28 shows that after 21 years all-cause morbidity is further delayed toward the end of life and that, so far, mortality is also being delayed in runners compared with controls
  • Studies on exercise as a possible cause of knee OA, in order of quality of evidence
  • Studies of lesser quality, usually case-control studies or cross-sectional surveys, have been conducted, which show similar results with high levels of exercise.36,40,42 Some of these suggest that athletes competing at high levels of activity when they are young are increasingly susceptible to OA later in life.13,44 Elite athletes have shown increased knee OA in some studies.27,39,41,43 Some authors cite trauma as a risk factor.21,22,2735 Genu varum was associated with knee OA in one paper.22 Occupational stresses, such as repetitive kneeling and stair climbing, can increase risk.19 Surprisingly, marathon running does not seem to induce changes in joints or increase the risk of OA in most studies.40,45,46 A large case-control study comparing swimmers with runners was unable to show a difference in lower-extremity pain or arthritis surgery associated with either accumulated mileage or number of years spent running.36 Certain sports, such as soccer and wrestling, increase the risk.
  • To summarize this literature:
  • The best evidence suggests that exercise, at least at moderate levels, does not accelerate development of knee OA. Running seems to be particularly safe.

  • There might be increased risk of OA with competitive sports participation, particularly early in life, and with competition at an elite level; however, the presence of OA does not lead to increased disability.

  • Risk of OA might be increased in the presence of obesity, trauma, occupational stress, and alignment problems of the lower extremities.

  • There is evidence for reduction in lower-extremity disability and all-cause disability in self-selected runners compared with controls.

  • There is some evidence for prolongation of lifespan in self-selected runners.

  • Case resolution

  • This man can be reassured that, as a self-selected runner, he will not develop accelerated knee OA as a result of his activity, and that his risk of disability might even be minimized as he ages because of his level of exercise. Although there is no evidence that a physician-imposed recommendation for the same level of activity in a sedentary person would be risk free, it is reassuring to note that activity at a moderate level with avoidance of extreme sports and trauma does not seem to increase the risk of knee OA. Knee x-ray scans would not be helpful for this man, as changes do not predict future appearance of clinical symptoms.
  • In the presence of knee OA, what is the effect of exercise on physical function, pain, and disability?

  • A 55-year-old woman has been experiencing increasing knee pain with physical activity for the past several years. She has been told by her physician that she presents early stages of knee arthritis on x-ray scans, and she occasionally uses over-the-counter anti-inflammatory medications for relief. She is slightly overweight and finds that she cannot lose weight by dieting. She is sedentary and is afraid to start exercising as an aid to weight loss because she is afraid that this will make her knee arthritis worse as she becomes older. She asks your advice.

  • Review of the literature addressing the effects of exercise on established symptomatic knee OA yields numerous good-quality level I studies in the form of Cochrane reviews and systematic reviews. There is, in fact, a systematic review evaluating available systematic reviews.50 Blinding is still a problem in some of the more vigorous interventions. There are also small problems with randomization, intention-to-treat analysis, compliance, and heterogeneity in the evaluation of these studies; however, all included studies are randomized controlled trials.
  • Studies of exercise in patients with known knee OA
  • Interventions examined include progressive resistance training,4952 aquatic exercise,47 land-based exercise,4853 intensity of life activities,51 aerobic training,52 and all physical modalities.50 Long-term effects of exercise interventions have been evaluated.54 Factors influencing prognosis for OA progression have also been identified.55 The following conclusions can be drawn from this literature: quadriceps strengthening, walking,
  • These studies pertain only to the effects of interventions on symptoms and degree of disability in patients previously diagnosed with knee OA. No clinical or x-ray evaluations were done.
  • The levels of exercise intervention were generally low or moderate.
  • There is demonstrated benefit for sedentary people, provided progressive structured activity is provided.51
  • There is little correlation between severity of OA symptoms at onset of activity and degree of benefit.55 here is probably an advantage of dynamic over static activity.51
  • Obesity is a prevalent comorbidity. Studies varied as to whether obese subjects benefited from exercise interventions,55 but the most inclusive study suggested benefit.50 Body fat reduction by exercise and diet, rather than weight reduction alone, was effective in reducing OA symptoms in a small controlled study.56 Therefore, it is suggested that weight loss need not be a prerequisite for OA improvement in overweight individuals. None of the exercise modalities demonstrated any harm in obese subjects.
  • Most of the benefits of exercise were measured for a short term.47,48,53 Long-term benefit was not demonstrated unless repeated “booster sessions” were provided.54
  • Exercise interventions all had small to moderate beneficial effects on pain. There were no dissenting studies.
  • All exercise interventions, with the exception of progressive resistance training, had a small to moderate beneficial effect on disability.
  • The benefits of land-based exercises can be similar to the relief obtained from nonsteroidal anti-inflammatory drugs.48 Generally, nonpharmacologic approaches to OA treatment are as effective as pharmacologic approaches.57
  • There is no indication that low to moderate exercise intervention causes increased pain or disability in knee OA.
  • Guidelines from the American College of Rheumatology58 and the European League Against Rheumatism,59 although generated in 2000, are consistent in recommending aerobic exercise, muscle strengthening, and preservation of joint mobility as central components of the nonpharmacologic approach to the treatment of knee OA. The 2007 recommendations of the Osteoarthritis Research Society International57 are more inclusive of the current literature and again stress the value of exercise, whether water-based, aerobic, muscle strengthening, or physiotherapy-based. Further, these guidelines stress that there are no statistical differences in the benefits derived from pharmacologic and nonpharmacologic modalities in the treatment of knee OA.57 Despite these findings, DeHaan et al,60 in a Canadian study at a teaching clinic, were rarely able to find documentation of the use of nonpharmacologic therapy. However, based on the evidence, judicious use of exercise is a compelling modality in the treatment of knee OA, and this intervention incurs little risk.
  • Case resolution

  • This woman can be reassured that gradually increasing exercise to a moderate level as a means of losing weight is unlikely to make her knee symptoms worse. She can also be told that there is a possibility that exercise can improve her knee symptoms as well. A plan for continuing long-term exercise will be important to both facilitate and maintain her weight loss and possibly reduce her knee symptoms. It is reasonable to suggest that, even if she achieves minimal weight loss, continued exercise will minimize both pain and disability. If she chooses land-based exercise, she might expect improvement in symptoms and disability similar to benefits obtained from nonsteroidal anti-inflammatory drugs, without the side effects. She might consider stopping the medication or switching to acetaminophen.
  • Conclusion

  • Individuals without knee OA who opt to exercise will not have increased progression of joint degeneration as a result of their increased physical activity; indeed, they can expect reductions in knee pain and all-cause disability as the years progress. Vigorous sports and activity leading to trauma should be avoided. Externally imposed recommendations for exercise will not necessarily produce the same results, as these studies have not yet been done.
  • Persons with knee OA who exercise to a moderate level can expect reduction in both knee pain and disability for the duration of their intervention. A long-term exercise program is unlikely to be harmful, but interventions of a longer duration have not been adequately studied. There is outstanding evidence for the benefit of exercise therapy in knee OA and some indication that it is underused as a treatment modality.
  • Levels of evidence

  • Level I: At least one properly conducted randomized controlled trial, systematic review, or meta-analysis
  • Level II: Other comparison trials, non-randomized, cohort, case-control, or epidemiologic studies, and preferably more than one study
  • Level III: Expert opinion or consensus statements

  • Notes

  • With more people living longer, maintenance of physical activity and prevention of premature disability are increasingly important for quality of life with longevity. It is important to understand the role of exercise in the etiology and natural history of knee osteoarthritis (OA), one of the most prevalent conditions leading to disability in old age.
  • Studies show that individuals without knee OA who opt to exercise will not have increased progression of joint degeneration as a result of the excercise; indeed, they can expect reductions in knee pain and all-cause disability as the years progress. Vigorous sports and activity leading to trauma should be avoided.
  • There is outstanding evidence for the benefit of exercise therapy in knee OA. Those with knee OA who do moderate exercise can expect reduction in knee pain and disability for the duration of their intervention. A long-term exercise program is unlikely to be harmful, but interventions of a longer duration have not been adequately studied.


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