Does tibia vara increase medial knee pain following cemented mobile-bearing unicompartmental knee arthroplasty? a prospective comparative study.

PURPOSE: To determine whether preoperative tibia vara increases medial knee pain (MKP) following cemented mobile-bearing unicompartmental knee arthroplasty (UKA). METHODS: This prospective study included 150 knees with anteromedial osteoarthritis undergoing cemented mobile-bearing UKA (Group I: 39 tibia vara; Group II: 111 normal tibia). Primary outcome was VAS for MKP, analysed by generalized estimating equations to account for bilateral cases. Secondary outcomes included Knee Society Score, Oxford Knee Score, Knee injury and Osteoarthritis Outcome Score, Forgotten Joint Score, Kujala Score, and anterior knee pain, assessed at six weeks to 24 months. RESULTS: VAS for MKP was never higher in Group I and did not differ at two years (0.2 ± 0.5 vs. 0.3 ± 0.7; p = 0.25); it was significantly lower in Group I at six months (0.2 ± 0.6 vs. 0.6 ± 1.3; p = 0.01), by margins below the minimal clinically important difference. Postoperative aTFA was lower in Group I (0.0° ± 2.5 vs. 3.4° ± 2.9; p < 0.001). No complications occurred in either group. CONCLUSION: Tibia vara does not increase MKP or adversely affect short-term clinical outcomes following cemented mobile-bearing UKA.