Dissecting a popliteal cyst after failed unicompartmental knee arthroplasty.

This report documents the first case of a popliteal cyst in a knee with failed unicompartmental knee arthroplasty (UKA). The cyst was treated successfully with the creation of a small communication hole between the posteromedial compartment and the popliteal cyst under direct arthroscopic visualization. This was followed by the replacement of a worn polyethylene insert via a small arthrotomy. Three months later, the popliteal mass had disappeared. This case suggests that a dissecting popliteal cyst may occur after UKA as one of the signs of a malfunction. It also suggests that treatment should be directed toward the joint and not the cyst itself.