Body weight and the knee joint

The IntroductionKnee Joint

Obesity and overweightness have long been known as risk factors for knee osteoarthritis and knee pain in general. Sadly as we age, even in masters athletes, the amount of body fat increases. The aim of this study was to examine the relationship between body composition (e.g. fat mass, muscle mass) and knee structure, including knee cartilage volume, cartilage defects and bone marrow damage. This study showed that fat mass was associated with increased cartilage defects and bone marrow lesions which are features of early knee osteoarthritis. In contrast, skeletal muscle mass was positively associated with cartilage volume, a great thing for healthy knees.

 

The Research

153 healthy subjects aged 25-60 years, 81% females, were recruited across a wide range of body mass indexes for a study examining the relationship between obesity and musculoskeletal disease. Magnetic Resonance Imaging (MRI) was performed on the dominant knee of each person. Cartilage volume, cartilage defects and bone marrow lesions were measured. Body composition was measured using dual X-ray absorptiometry to determine fast and muscle mass in each person.

The Results

There was an 81 mm3 increase in cartilage volume for every 1 kg increase in skeletal muscle mass. Fat mass was not significantly associated with cartilage volume. Fat mass, but not skeletal muscle mass, was a risk factor for cartilage defects and bone marrow lesions. For every 1 kg increase in total body fat there was a 131% increased risk of cartilage defects and 109% increased risk of bone marrow lesions.

The So What?

In a healthy population, fat mass was associated with increased cartilage defects and bone marrow lesions which are features of early knee osteoarthritis. In contrast, skeletal muscle mass was positively associated with cartilage volume, which may be due to coinheritance, environmental factors associated with cartilage accrual or a protective effect of increased muscle. The good news is that weight-bearing exercise and weight training of the legs help maintain or increase muscle mass into older age.

 Berry, P.A. and others (2010) The relationship between body composition and structural changes at the knee. Rheumatology (Oxford). Aug 18. [Published electronically ahead of print]

Photo from: http://www.flickr.com/photos/17657816@N05/1972120746/