Acutely injured knee: effect of MR imaging on diagnostic and therapeutic decisions.

PURPOSE: To assess the effect of knee magnetic resonance (MR) imaging on the diagnosis and management of acute knee injury.

MATERIALS AND METHODS: Two orthopedic knee surgeons prospectively completed pre- and post-MR imaging questionnaires on 84 of 91 consecutive patients with acute knee injury. The pre- and post-MR imaging clinical diagnoses, certainty regarding these diagnoses, other diagnostic tests, and subjective impression of the usefulness of MR imaging were determined.

RESULTS: Seven hundred thirty-one of 840 pre- and post-MR imaging diagnoses agreed. Agreement was lowest for medial meniscal injuries (54 of 84). Significantly fewer meniscal injuries were suspected after MR imaging (P < .05). In 60 patients, the orthopedist changed at least one of the 10 potential diagnoses after MR imaging. Clinical diagnostic certainty increased by a mean of 14% for all diagnoses. The increase in diagnostic certainty was greatest for medial meniscal injuries (30%), followed by lateral meniscal injuries (21%). The proposed management changed in 41 patients, resulting in significantly fewer arthroscopic procedures (P < .01). The post-MR imaging management plans included 37% (27 of 73) fewer arthroscopic procedures.

CONCLUSION: MR imaging affects the diagnosis and management of acute knee injury by decreasing the number of arthroscopic procedures, improving clinician diagnostic certainty, and assisting in management decisions.