Q: I’ve seen several people lately who are bowlegged—or bandy-legged as my father called it. What could be causing that besides rickets, which I thought wasn’t an issue anymore in the U.S.?
A: Medically called genu varum, bowlegs are characterized by legs that curve outward, leaving a space between the knees. It can occur in one or both legs. But aside from rickets (typically the result of a vitamin D deficiency, which is rare in developed countries today because of fortification of baby formula and other foods), there are many other possible causes for bowlegs. These include a bone fracture of the leg that didn’t heal properly, a bone tumor or bone infection, or various disorders that affect bone metabolism (Paget’s disease, brittle bone disease, and achondroplasia). But a very common cause of bowlegs is Blount’s disease, a genetic abnormality of bone growth. Leg-length differences or obesity can also contribute to bowlegs over time.
It’s normal to see bowlegs in newborn babies, after which the angle of the legs straightens out, typically within the first two years or so of life—though some people are born with bowlegs that remain that way.
Interestingly, several papers have reported an increased risk of bowlegs in young soccer players and have found that the extent of the deformity increases the longer they engage in the sport. It’s thought that bowlegs could be related to muscle imbalances that occur with frequent soccer playing during youth, such that the muscles of the inner thigh shorten and become stronger than those on the outer thigh. The teen years—when long bones rapidly increase in length as part of growth spurts—are a particularly vulnerable time for developing leg-related problems such as bowlegs. An older study in Medicine & Science in Sports & Exercise reported that 73 percent of veteran soccer players had X-ray evidence of bowlegs.
Bowleggedness is not simply an aesthetic issue. Bowing of the legs puts strain on the knees, which, in turn, increases damage to the cartilage and other connective tissues there, thus increasing the risk of knee osteoarthritis or accelerating progression of the condition. And in what is a vicious circle, knee osteoarthritis (especially if severe) is believed over time to increase bowleggedness.
This article first appeared in the UC Berkeley Wellness Letter.
Also see Knock Knees: Causes and Treatments.