Dissociation of the tibial component in total knee replacements.

Dissociation of the polyethylene component from its metal backing in total knee arthroplasty is a recognized problem regarding the patella. Two cases of dissociation of the metal-backed tibial component from its polyethylene articulating surface presented symptoms of prosthesis failure: persistent pain, swelling, sensations of instability, and gait difficulty. Investigations ruled out prosthesis malalignment, loosening, and sepsis. Precise diagnosis of dissociation of the tibial component was made by diagnostic arthroscopy.