Effect of Long-Term Vigorous Physical Activity on Healthy Adult Knee Cartilage
Teichtahl AJ, et al. Med Sci Sports Exerc. 2012 44:6, 985-992.
Effect of Leisure Time Physical Activity on Severe Knee or Hip Osteoarthritis Leading to Total Joint Replacement: a Population-Based Prospective Cohort Study
Ageberg E, et al. BMC Muscoloskeletal Disorders. 2012, 13:73.
Osteoarthritis has often been described as “wear and tear” on the joint. However, previous research has shown that the pathogenesis is not this clear cut. Several studies demonstrate that increased physical activity can actually prevent osteoarthritis; however, other studies have shown just the opposite. These two papers by Teichtahl and Ageberg look to further characterize the effects of physical activity on osteoarthritis incidence. The Ageberg et al. study quantified leisure time physical activity in 28,320 participants with a mean age of 59 years using a questionnaire to determine duration and intensity of activities. The outcome in this study was the incidence of hip or knee replacement over the study period of 11 years. The study showed no significant association between knee or hip replacement surgery and higher leisure time activity levels. Among women, there was a significant reduction in the incidence of hip replacement with increased activity. For women in the fourth quartile (the most physically active), the relative risk of hip replacement was 0.66 (confidence interval: 0.48-0.89). The Teichtahl et al. article examined knee structural changes on magnetic resonance (MR) images among 297 adults aged 50-79 years at baseline and 10 years later. The authors characterized vigorous physical activity levels using a questionnaire asking about frequency/duration of activities leading to sweating or shortness of breath (their definition of vigorous). This study found that in knees with pre-existing bone marrow lesions (a bone lesion associated with decreased knee joint health, n = 37), continued participation in vigorous physical activity was associated with an increase in cartilage defects in the medial tibiofemoral compartment. However, in this group, there was no significant relationship between persistence of vigorous physical activity and change in cartilage volume (i.e. the thickness of the cartilage pad). Furthermore, in the group without bone marrow lesions at baseline, there was no association between the persistence of vigorous physical activity over 10 years and changes in cartilage defects or volume; or between the persistence of vigorous physical and presence of bone marrow lesions.
It is difficult to study the effect of physical activity on joint health. Using questionnaires to determine activity often cannot differentiate specific activities such as repetitive high-impact exercises and deep squats that may impact joint health and questionnaires rely on the truthfulness of the participants. Determining the severity of arthritis is also tricky. Using joint replacement as a surrogate for arthritis as in the Ageberg paper is useful because it avoids the pitfalls of using radiographic or self-reported symptoms to determine disease severity; however, one can make conclusions only about severe, end-stage osteoarthritis and various factors can influence who chooses or is able to have a total knee replacement. Using imaging to characterize arthritis as in the Teichtahl paper is also potentially misleading because MR imaging findings do not always correlate with clinically symptomatic disease. Interestingly, in the Teichtahl paper, over the course of the 10 year study period, 26 subjects were lost to follow-up for various reasons; however none were lost to follow up because of knee joint replacement. This may indicate that despite having MR imaging findings of cartilage defects in patients with persistent vigorous physical activity, these patients may not be particularly symptomatic. This paper found that persistent vigorous physical activity is detrimental to MR imaging measurements of knee osteoarthritis in a subgroup population (those with bone marrow lesions); whereas, the Ageberg paper found that increased physical activity is protective against hip replacement in a subgroup population (women). How do you advise your patients with osteoarthritis? Do you think more activity is better, or less? Does timing of activity in relation to disease onset matter? If someone has structural changes on imaging indicating poor joint health, would you advise them to cut back on physical activity?
Written by: Hallie Labrador, MD MS and Marc I. Harwood, MD
Reviewed by: Jeffrey Driban
Ageberg E, Engström G, Gerhardsson de Verdier M, Rollof J, Roos EM, & Lohmander S (2012). Effect of leisure time physical activity on severe knee or hip osteoarthritis leading to total joint replacement: a population-based prospective cohort study. BMC musculoskeletal disorders, 13 (1) PMID: 22595023
Teichtahl AJ, Wluka AE, Wang Y, Forbes A, Davies-Tuck ML, English DR, Giles GG, & Cicuttini FM (2012). Effect of long-term vigorous physical activity on healthy adult knee cartilage. Medicine and science in sports and exercise, 44 (6), 985-92 PMID: 22215179