Influence of magnetic resonance imaging on a knee arthroscopy waiting list.

Magnetic resonance imaging (MRI) scans were performed on 155 patients who had been placed on a diagnostic knee arthroscopy waiting list 4 to 18 months previously. In all, 32 per cent were removed from the waiting list following this investigation. A total of 24 patients on the waiting list improved spontaneously, including 13 per cent of those with MRI-demonstrable meniscal tears. MRI had an accuracy of 93 per cent, a sensitivity of 100 per cent and a specificity of 67 per cent using arthroscopy as a standard; the false-positive rate was 7 per cent and the false-negative rate 1 per cent. It is concluded that the use of MRI can reduce the requirements for diagnostic arthroscopy, but that the ideal time for MRI is not clear.