The correlation between preoperative patellar tilt and clinical outcomes following unicompartmental knee arthroplasty

To investigate the association between preoperative patellar tilt angle and clinical outcomes following unicompartmental knee arthroplasty (UKA).

In this retrospective study, 148 UKA patients were stratified into normal (patellar tilt < 10°, n = 99) and abnormal (≥ 10°, n = 49) groups. Radiographic alignment -including the hip-knee-ankle angle (HKA), mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA), and posterior tibial slope were compared. Clinical outcomes were assessed using the Visual Analog Scale (VAS) for pain, the Hospital for Special Surgery (HSS) score, the Feller patellar score, and the incidence of anterior knee pain (AKP). Additional patellofemoral parameters (patellar shift, Caton-Deschamps index, Iwano classification) were also analyzed.

Postoperative mechanical alignment (HKA, mLDFA, MPTA) was successfully corrected to the ideal range (approximately 3° of physiological varus) in both groups, with no significant differences. However, clinical outcomes were significantly worse in the abnormal group compared to the normal group: higher postoperative VAS scores (median 1 vs. 0, p = 0.010), lower HSS scores (median 83 vs. 85, p = 0.000), lower Feller scores (median 19 vs. 20, p = 0.000), and a higher incidence of AKP (12.24% vs. 3.03%, p = 0.027). No significant intergroup differences were found in the additional patellofemoral parameters.

A preoperative patellar tilt angle ≥ 10° is significantly associated with inferior early clinical outcomes and a markedly increased risk of AKP after UKA, despite successful mechanical alignment correction. Preoperative assessment of patellar tilt may provides valuable prognostic information and may help identify patients requiring heightened intraoperative attention to patellofemoral kinematics or tailored rehabilitation.