The incidence of pathology detected by magnetic resonance imaging of the knee: differences based on the specialty of the requesting physician.

The usage patterns of magnetic resonance imaging (MRI) by orthopedic and nonorthopedic surgeons were studied. A sample consisting of the radiologist reports from all knee MRIs in a single year at our institution were reviewed. Studies to evaluate tumors or infections were excluded. Reports were classified as normal or demonstrating degenerative joint disease, meniscal tears, cruciate ligament pathology, collateral ligament pathology, focal chondral defects, chondromalacia patella, cysts, extensor mechanism dysfunction, intraosseous edema, or fractures. Six hundred eighteen reports were reviewed. The combined incidence of a normal study or one that found only degenerative joint disease was 45% for nonorthopedic surgeons and 27.6% for orthopedic surgeons (P<.00001). Given the higher incidence of normal findings in studies ordered by nonorthopedic surgeons, these physicians probably use MRI more for screening whereas orthopedic surgeons are more apt to use it for confirmation. Therefore, if clinical guidelines for using MRI are to be established, differences in use as a function of specialty must be acknowledged.