The femoral intercondylar notch width was measured in 93 patients with chronic anterior cruciate ligament (ACL) insufficiency (Group 1), in 62 patients with an acute tear of the ACL (Group 2), and in 38 fresh anatomic specimen knees (Group 3). In six of the specimen knees, further anatomic studies of the intercondylar notch were performed after tissue removal. The average intercondylar distance was 16.1 mm in Group 1, 18.1 mm in Group 2, and 20.4 mm in Group 3. All differences were highly significant. The intercondylar notch was wider in the posterior part and had no crossing bony ridges but had generally concave walls, which provided a functional shelf for the ACL to insert on the lateral side. Significant osteophyte formation and stenosis of the anterior outlet of the intercondylar notch occur early in the ACL-deficient knee. A narrow anterior outlet of the intercondylar notch without osteophytes was also found in knees with an acute ACL rupture. At reconstruction of the ACL, notchplasty should be performed concomitantly.