Bearing dislocation is a unique complication of mobile-bearing unicompartmental knee arthroplasty (UKA), with diverse underlying mechanisms. This article reports a rare mechanism of bearing dislocation following mobile-bearing UKA, which was probably associated with the new-onset rheumatoid arthritis (RA) leading to anterior cruciate ligament (ACL) insufficiency—aiming to highlight this uncommon etiology and its implications for clinical practice. A 53-year-old woman presented with acute right knee pain and restricted mobility one day prior to admission, who was treated by mobile-bearing UKA for anteromedial osteoarthritis two years ago. Radiographs revealed bearing dislocation in this patient. Laboratory evaluation revealed elevated inflammatory markers (CRP 71.59 mg/L, ESR 74 mm/h) and positive RA serology(anti-CCP 39.09 U/mL, RF 32.4 IU/mL). Periprosthetic joint infection was rigorously excluded through multiple methods. The patient responded well to short-term corticosteroids and underwent one-stage revision total knee arthroplasty. Intraoperatively, extensive chronic synovitis, bearing dislocation, and severe ACL erosion/laxity due to synovial proliferation were observed. Histopathology confirmed synovial hyperplasia with dense lymphoplasmacytic infiltration and lymphoid follicle formation. Following standardized anti-rheumatic therapy, the patient regained satisfactory knee function with normalized inflammatory markers at 12-month follow-up. This case highlights that in patients who was present with delayed pain and elevated inflammatory markers after UKA. Inflammatory joint diseases such as RA should be included in the differential diagnosis alongside infection. Appropriate serological screening and multidisciplinary collaboration with rheumatology are essential for optimal management. As a single case report, these findings are hypothesis-generating and warrant confirmation in larger studies.
Liu et al. (Mon,) studied this question.