Posterior tibial tendon dysfunction: Imperfect specificity of magnetic resonance imaging.

MRI is frequently used in the evaluationand treatment of tibialis posterior tendon (PTT) dysfunction. MRI is reported to have sensitivity up to 95%, with 100% specificity, in the detection of rupture of the PTT. We present three cases where MRI demonstrated complete or partial rupture of the PTT, where subsequent surgery showed an intact PTT with tenosynovitis. In all cases, there was a source of inflammation external to the tendon. It is hypothesized that this exogenous origin of inflammation caused changes in the MRI signal in the PTT that resemble that seen in ruptures. These cases show that in the presence of inflammation near the tibialis posterior tendon, the MRI may falsely indicate a high-grade rupture of the tendon. Recommendations for treatment of suspected PTT rupture in the presence of significant other sources of inflammation are proposed.