However, this effect of weight on the progression was not present in all
knees, but was limited to the knees of moderately malaligned legs. In neutrally
aligned limbs on one end of the spectrum and severely malaligned limbs on the
other, body weight had no effect on progression of knee OA.
Researchers explain that with severe malalignment, the extreme stress already
placed on the cartilage may be the only risk factor required for further
deterioration. With neutral alignment, the increased body weight would be
equally distributed across the knee joint, therefore protecting it against
injury from extra weight.
So, why would knees in moderately malaligned limbs be most susceptible to
injury from increased body weight? The study authors say malalignment increases
stress on the joint, and the additional weight is enough to accentuate the
cartilage injury. Researchers say losing weight may relieve stress and slow
disease progression for this group.
For the study, 228 individuals with knee OA were examined over 30 months. The
body mass index was also computed for each person. Results show for each
two-unit increase in BMI, there was an 8-percent increase in the risk of
progression in moderately malaligned legs.
The researchers say their findings need to be confirmed in other studies, but
they may have broad implications for the effect of body weight and other risk
factors on OA.
SOURCE: Arthritis & Rheumatism, 2004;50:3904-3909
