Patellofemoral Joint Replacement for Isolated Patellofemoral Osteoarthritis: Mid- to Long-Term Survivorship and Functional Outcomes

Background/Objectives: Patellofemoral joint (PFJ) replacement is a bone-preserving option for isolated patellofemoral osteoarthritis; however, reported survivorship and failure patterns remain variable. This study evaluated implant survivorship, functional outcomes, reoperations, and failure mechanisms following PFJ replacement using standard second-generation implant systems, with or without patellar resurfacing. Methods: We retrospectively reviewed a consecutive cohort of 39 patients (48 knees) who underwent PFJ replacement for isolated patellofemoral osteoarthritis between 2011 and 2021. Median age at surgery was 59 years, and median body mass index (BMI) was 31 kg/m2. Median follow-up for clinical and revision surveillance was 9 years (IQR 8–10). Functional outcomes were assessed using the Oxford Knee Score (OKS) and SF-12 Physical and Mental Component Scores (PCS and MCS). Implant survivorship was analyzed using Kaplan–Meier methodology, with conversion to total knee arthroplasty (TKA) as the endpoint. Statistical analyses were primarily descriptive and exploratory because only five TKA revisions occurred. Results: Median OKS improved from 19 (IQR 16–24) preoperatively to 36 (IQR 24–42) at the latest follow-up, with a median paired improvement of 17 points. SF-12 PCS improved from 25 to 47, and SF-12 MCS from 36 to 55. Eight knees (16.7%) underwent non-revision reoperation, and five knees (10.4%) underwent conversion to TKA. All TKA revisions were performed for the progression of tibiofemoral osteoarthritis. Kaplan–Meier survivorship free from TKA revision was 89.6% at 9 years (95% CI 76.8–95.5). No clear difference in TKA-free survivorship was detected between resurfaced and non-resurfaced knees. Conclusions: PFJ replacement demonstrated substantial functional improvement and mid- to long-term survivorship comparable to published registry ranges in a selected cohort with isolated patellofemoral osteoarthritis. TKA revision was uncommon and was attributable to the progression of tibiofemoral osteoarthritis. Because of the retrospective design, small cohort size, bilateral cases, and limited number of revision events, subgroup and risk-factor analyses should be interpreted as exploratory.