Magnetic resonance imaging of the postoperative meniscus.

Imaging of the postoperative meniscus is a challenge. Nevertheless, magnetic resonance imaging (MRI) of the symptomatic knee after meniscal surgery is a valuable diagnostic study of both the menisci and the entire joint. At present, symptomatic patients who have had partial meniscectomy of less than 25% may be evaluated by MRI. For those with partial meniscectomy of greater than 25% or after meniscal repair, direct or indirect magnetic resonance arthrography (MRA) should be considered. Currently, the decision of whether to perform direct (intra-articular) versus indirect (intravenous) MRA must be reviewed on a case-by-case basis considering both the patient's ability to tolerate intra-articular injection and whether a significant effusion already exists, which will imbue the tear with synovial fluid (making intra-articular injection of less importance). In such cases of significant effusion, indirect MRA would be preferred. If MRI or MRA is contraindicated, computed tomography arthrography seems a promising alternative. For a patient who has undergone meniscal allograft transplantation, MRI seems adequate for detecting meniscocapsular healing, allograft extrusion, and allograft tear. Future improvements in MRI sequencing may obviate the need for invasive modalities.