[Knee pain of unknown origin after total knee prosthesis in a patient with chronic polyarthritis]

Persisting pain after TKA is a frequent problem. The most frequent differential diagnoses are aseptic loosening, malpositioning or a prosthetic joint infection. Retropatellar pain, functional or psychosomatic cause should be taken into account, too. An acute episode in patients with a rheumatoid arthritis should be ruled out. Insufficiency fractures, which can also be found in the presented case, are more often in patients with rheumatoid arthritis. The insufficiency fracture was detectable in the MRI and shows an uncommon, non-described localization. To prevent a loss of mobility of fractures close to the joint a surgical stabilizing is recommended, leading to quick healing.