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.