We studied the results of bone scans in 50 consecutive patients with symptomatic, unilateral, chronic anterior cruciate ligament (ACL) tears. All patients had failed conservative therapy and underwent radionuclide imaging of the knee prior to arthroscopic ACL reconstruction. The scintigraphic activity in each of the three knee compartments was quantitatively scaled from 1 (normal scintigraphic activity) to 4 (marked activity). Quantitative activity in each of the three compartments was correlated with plain radiographic, arthroscopic, and clinical findings. All but four of the scans (92%) showed abnormal scintigraphic activity. The quantitative activity was highest overall in the medial compartment (2.9), followed by the lateral (2.4) and patellofemoral compartments (1.9). In the subgroup of patients with normal menisci (10 patients), most of the abnormal activity was in the lateral compartment (2.9), implying that when the medial meniscus remains competent in the presence of a torn ACL, there is increased stress on the lateral compartment. There was little correlation with scintigraphy and roentgenographic changes, except in the presence of moderate or severe radiographic degenerative arthritis. Similarly, there was little correlation between increased scintigraphic activity and chondromalacia. These results provide a baseline for future studies that use scintigraphic imaging in monitoring restoration of bone homeostasis following ACL reconstruction.