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Knee Cartilage Morphologic Characteristics and Muscle Status of Professional Weight Lifters and Sprinters

A Magnetic Resonance Imaging Study

Christian Gratzke, MD^,*, Martin Hudelmaier, MD^,, Wolfgang Hitzl, PhD^||, Christian Glaser, MD^¶ and Felix Eckstein, MD^,

From the Musculoskeletal Research Group, Institute of Anatomy, Ludwig-Maximilians-Universität München, Munich, Germany, the Institute of Anatomy & Musculoskeletal Research, Paracelsus Medical University, Salzburg, Austria, Chondrometrics GmbH, Ainring, Germany, the ^|| Research Office, Paracelsus Medical University, Salzburg, Austria, and the ^¶ Institute for Clinical Radiology, Klinikum Großhadern, Ludwig-Maximilians-Universität München, Munich, Germany

^* Address correspondence to Christian Gratzke, MD, Department of Urology, Klinikum Großhadern, Ludwig-Maximilians-Universität München, Marchioninistr. 15, 81377 Munich, Germany (e-mail: christian.gratzke{at}med.uni-muenchen.de).

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.

Key Words: cartilage • muscle • functional adaptation • magnetic resonance imaging