Unicompartmental knee arthroplasty versus total knee arthroplasty: Which type of artificial joint do patients forget?

Purpose: During recent years, there has been an intensive growth of interest in the patient’s perception of functional outcome. The Forgotten Joint Score (FJS) is a recently introduced score that measures joint awareness of patients who have undergone knee arthroplasty and is less limited by ceiling effects. The aim of this study was to compare the FJS between patients who undergo medial unicompartmental knee arthroplasty (UKA) and patients who undergo total knee arthroplasty (TKA) 1 and 2 years post-operatively. Methods: This prospective study compares the FJS at a minimum of one (average 1.5 years, range 1.0–1.9) and a minimum of 2 years (average 2.5 years, range 2.0–3.6) post-operatively between patients who underwent medial UKA and TKA. Results: One-hundred and thirty patients were included. Sixty-five patients underwent medial UKA and 65 patients underwent TKA. At both follow-up points, the FJS was significantly higher in the UKA group (FJS 1 year 73.9 ± 22.8, FJS 2 year 74.3 ± 24.8) in contrast to the TKA group (FJS 1 year 59.3 ± 29.5 (p = 0.002), FJS 2 year 59.8 ± 31.5, (p = 0.004)). No significant improvement in the FJS was observed between 1- and 2-year follow-up of the two cohorts. Conclusion: Patients who undergo UKA are more likely to forget their artificial joint in daily life and consequently may be more satisfied. Level of evidence: II.