M.R. imaging of the knee: a prospective trial using a low field strength magnet.

A double blind prospective study involving fifty patients was performed to assess the diagnostic accuracy of knee MR Imaging using a 0.3 Tesla low field strength scanner. The study compared MR Imaging with arthroscopy. The overall accuracy found for the detection of meniscal tears was 92% and cruciate ligament tears 95%. These results compare favourably with other diagnostic modalities including knee arthroscopy. MR Imaging is good at showing meniscal lesions, especially cleavage tears, though some bucket-handle tears produced no MR abnormality. MR Imaging is very accurate at demonstrating complete cruciate ligament tears. Partial cruciate ligament tears often produced no positive MR findings and in no patients could any features be found to indicate ligamentous laxity.