Articular cartilage surfaces of 49 human patellae and 24 distal femora were characterized by identifying distinctive features using surface curvature analysis. Paired specimens from the same donor generally exhibited natural symmetry, so only results from non- paired specimens were considered (39 patellae, 19 femora). In 23 of 39 patellae, proximal median and lateral transverse ridges extended to form an "oblique" ridge resembling a skewed "lambda" (l). Most patellae (37 of 39) exhibited only a single lateral transverse ridge. Most (32 of 39) had an "odd" facet. All but one patella exhibited a concave depression in the lateral and medial facets, and a sellar area in the proximal region. All distal femoral surfaces exhibited a sellar trochlea. The concavity of the trochlea was greatest in the posterior aspect near the inter-condylar notch.