Pain distribution and functional outcomes after lateral unicompartmental versus total knee arthroplasty for isolated lateral compartment osteoarthritis with anterior knee pain.

Background: Isolated lateral compartment osteoarthritis (LCOA) with anterior knee pain (AKP) represents a lateral tibiofemoral-patellofemoral phenotype. Evidence comparing lateral unicompartmental knee arthroplasty (LUKA) and total knee arthroplasty (TKA) in this subgroup is limited for compartment-specific pain. This study compared pain distribution and function when both procedures were performed within a lateral parapatellar pathway. Methods: This retrospective cohort included 115 patients with isolated LCOA and AKP who underwent LUKA ( Results: Baseline characteristics and preoperative scores were comparable. LUKA was associated with shorter operative time, less blood loss, and shorter hospital stay. At 3 months, KSS was higher and WOMAC lower after LUKA, with lower LC-VAS and similar PFC-VAS. At 24 months, no statistically significant between-group differences were detected in KSS, WOMAC, LC-VAS, and PFC-VAS. Regression estimates were small (KSS adjusted mean difference 0.51, 95% confidence interval (CI) -0.58 to 1.60, and WOMAC -0.62, 95% CI -1.85 to 0.62). Propensity score-weighted estimates were consistent, and 95% CIs remained within published minimal clinically important difference (MCID) thresholds for KSS (5 points) and WOMAC total (10 points). No revisions occurred after LUKA. One infection treated with debridement, antibiotics, and implant retention occurred after TKA. Conclusion: Within this standardised pathway, LUKA enabled faster early recovery and lower lateral pain with less surgical burden, while no statistically significant between-group differences were detected in 24-month pain distribution or function. The data primarily describe early recovery trajectories and pain distribution in this phenotype and warrant multicentre confirmation.