In the assessment of acute knee pain following recent trauma frequently related to sporting activities, bone scintigraphy was performed on 52 patients; in 40 of these patients, scintigraphy immediately preceded arthroscopy. SPECT was critical in providing delineation and siting of the abnormalities; this would not have been feasible with conventional planar imaging in 45 of the patients. Multiple sites of focal uptake were frequently visualized at ligamentous insertions or in intra-articular areas of cartilaginous erosion. Damaged anterior cruciate ligaments were only identified in 5 out of 10 patients, occurring when there was avulsion of the tibial attachment, but changes resulting from patellar injury were demonstrated in all 8 patients. The most characteristic scintigraphic change resulted from meniscal tears, which was diagnosed in 31 out of 35 patients in whom the lesion had been suspected clincally. In the identification of this common injury, SPECT had a sensitivity of 88%, specificity of 87%, and diagnostic accuracy of 88%. Thus, although trauma readily induces scintigraphic abnormalities in and around the knee, the patterns of alteration associated with particular lesions can be identified by SPECT and can provide considerable assistance in management, particularly in determining the need for arthroscopy.