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
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

Related Posts:

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