Objectives-To compare objectively the shape of the intercondylar notch in human osteoarthritic and non-osteoarthritic femora. Methods-A sample of 96 human femora from a large skeletal population were selected for study. These femora included subjects with evidence of late stage osteoarthritis (that is, with eburnation present) and subjects with no such evidence. The distal end of the femur, viewed axially, was recorded with a video camera, and digitised computer images were produced. The outline of the intercondylar notch was extracted and represented mathematically as two functions. A functional principal components analysis was used to identify important modes of shape variation. These variations in shape were compared between eburnated and noneburnated femora. Results-A statistically significant diVerence in the shape of the intercondylar notch was found between the two groups. The diVerence related mostly to the shape of the edge of the medial condyle: in the non-osteoarthritic group this tended to exhibit a concavity; in the osteoarthritic group it tended to be straight. Conclusions-This observed diVerence may be a predisposing factor to the development of osteoarthritis. The morphology of the intercondylar notch is related to the functioning of and possible damage to the cruciate ligaments, and damage to the cruciate ligaments is a known risk factor for osteoarthritis. Alternatively, this difference may be due to bony remodelling secondary to the onset of osteoarthritis, perhaps in response to altered biomechanics. (Ann Rheum Dis 2001;60:968-973) Osteoarthritis (OA) of the knee is a common, painful, and debilitating condition. It aVects up to 30% of Western populations over the age of 65, 1 presenting a large burden for healthcare services.