Patella position is not a determinant for anterior knee pain 10 years after balanced gap total knee arthroplasty.

PURPOSE: Incidence of anterior knee pain after total knee arthroplasty (TKA) is reported to be between 4 and 49 %. The incidence of AKP at long-term follow-up and possible determinants after cruciate cruciate-retaining TKA were investigated.
METHODS: A 10-year follow-up of a cohort of 55 patients (63 TKAs), who received the balanSys™ cruciate-retaining total knee system (Mathys Ltd, Bettlach, Switzerland) between 1999 and 2002, was performed. Patients had undergone the balanced gap technique, with either a fixed bearing or an AP-glide bearing. Standardised diagnostic questions regarding AKP were collected and categorised into two groups: those with and without AKP. The lateral patellar tilt, patellar displacement measurement and modified Insall-Salvati ratio were used for patella position evaluation on skyline radiographs. The Knee Society Score (KSS), the Knee Osteoarthritis Outcome Score (KOOS) and Numerical Rating Scales (NRS) for pain and satisfaction were obtained at follow-up.
RESULTS: Sixteen patients in the study population experienced AKP. Incidence of AKP (fixed bearing 13/44; AP-glide bearing baring 3/17) was not dependent on type of insert (n.s.). There were no statistical differences in patella position and tibiofemoral contact point between the AKP group and the no AKP group (n.s.). KSS, KOOS, NRS-pain and NRS-satisfaction were significantly lower for the patients with AKP (all p < 0.05).
CONCLUSION: Twenty-six percentage of the patients experienced AKP 10 years after balanced gap TKA. Postoperative patella positioning was not found to be a determinant for anterior knee pain after TKA. However, patellar displacement does not seem completely favourable. Moreover, type of bearing was not found a determinant for AKP at long-term follow-up. LEVEL OF EVIDENCE: Lower quality prospective cohort study (<80 % follow-up, patients enrolled at different time points in disease), Level II.