Knee cartilage morphologic characteristics and muscle status of professional weight lifters and sprinters: a magnetic resonance imaging study.

BACKGROUND

Whereas muscle and bone mass have been shown to strongly depend on mechanical stimulation (loading history), this relationship has not been established for articular cartilage.

HYPOTHESIS

Subjects with high muscle strength display thicker knee cartilage and larger joint surface areas than nonathletic volunteers, and knee cartilage morphologic characteristics correlate more strongly with muscle force than with muscle cross-sectional areas.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Fourteen young, healthy adult professional athletes (7 weight lifters and 7 bobsled sprinters) were examined and compared with 14 adult nonathletic volunteers who had never performed strength training. Muscle moments were measured with a dynamometer and muscle cross-sectional areas and knee cartilage morphologic characteristics with magnetic resonance imaging.

RESULTS

Weight lifters and sprinters displayed significantly (P < .001) larger extensor muscle moments and cross-sectional areas. They showed significantly greater (P < .01) patellar cartilage thickness than nonathletic volunteers (+14% [95% confidence interval, 6% to 22%] and +17% [95% confidence interval, 9% to 26%], respectively) but no significant differences in the cartilage thickness of the other knee joint cartilage plates or joint surface areas. Muscle moments did not correlate more strongly with knee cartilage volume or thickness than muscle cross-sectional areas of the thigh.

CONCLUSIONS

Direct measurements of muscle forces do not predict cartilage thickness more accurately than muscle cross-sectional areas. These findings suggest that cartilage thickness has much less ability, if any, to adapt to mechanical loading than muscle. Large cohorts of athletes will need to be studied to detect potentially significant differences in cartilage versus nonathletic controls.