Is a long leg a risk for hip or knee osteoarthritis?

Background and purpose - 7% of the asymptomatic population has leg-length inequality (LLI) greater than 12 mm. It has been proposed that LLI of >5 mm can be associated with an increased risk of osteoarthritis (OA) of the knee and hip. We studied a possible association between LLI and OA of the knee and hip joint. Patients and methods - We followed 193 individuals (97 women, 96 men) for 29 years. The initial mean age of the participants was 43 (34-54) years, and they had no clinical histories or signs of leg symptoms. The initial standing radiographs of their hips were re-examined and measured for LLI and signs of OA. None had any signs of OA. At the follow-up, data on performed hip or knee arthroplasties were obtained. Results - 24 (12%) of the subjects had no discernible leg-length difference, 62 (32%), had LLIs of 1-4 mm, 74 (38%) of 5-8 mm, 21 (11%) of 9-12 mm, and 12 (6%) of over 12 mm. 16 (8%) of the subjects had undergone arthroplasty for primary OA during follow-up, and of those, 8 for both hip and knee OA. 10 individuals had undergone an arthroplasty of the longer leg and only 3 of the shorter leg. In the group of equal leg length, 3 had had an arthroplasty of hip or knee. Interpretation - We noted that hip or knee arthroplasty due to primary OA had been done 3 times more often to the longer leg than to the shorter.