Forgetting the knee after high tibial osteotomy versus unicompartmental knee arthroplasty

Background: High tibial osteotomy (HTO) and unicompartmental knee arthroplasty (UKA) are widely used surgical options for the treatment of medial compartment knee osteoarthritis. While conventional outcome measures primarily focus on pain relief and functional improvement, joint awareness–based patient-reported outcome measures may provide a more comprehensive assessment of surgical success. The Forgotten Joint Score (FJS) evaluates the extent to which patients are able to “forget” their operated joint during daily activities and has been rarely used in direct comparisons between HTO and UKA. The aim of this study was to compare clinical and functional outcomes, including joint awareness, between patients treated with HTO and UKA. Methods: This retrospective study included patients who underwent open-wedge HTO or mobile-bearing UKA for anteromedial knee osteoarthritis between February 2011 and August 2022. Patients with complete clinical and radiological data and a minimum follow-up of one year were included. Clinical outcomes were assessed using the Oxford Knee Score (OKS), Visual Analog Scale (VAS), Knee Society Score (KSS), Knee Society Functional Score (KSS-Function), and Forgotten Joint Score (FJS). Preoperative radiographic severity was evaluated using the Kellgren–Lawrence classification. Statistical comparisons between groups were performed using appropriate parametric and non-parametric tests. Results: A total of 83 patients were included (52 HTO, 31 UKA). Patients in the UKA group were significantly older and had higher preoperative Kellgren–Lawrence grades than those in the HTO group (p < 0.05). Postoperatively, there was no significant difference between groups in OKS or VAS scores (p > 0.05). However, both the KSS knee score and KSS functional score were significantly higher in the UKA group (p = 0.013 and p = 0.020, respectively). The FJS was also significantly higher in patients treated with UKA compared with HTO (p = 0.006), indicating lower joint awareness. Conclusions: Despite being performed in an older patient population with more advanced radiographic osteoarthritis, UKA demonstrated superior functional and patient-centered outcomes compared with HTO. The significantly higher FJS scores suggest that UKA may provide a more “natural” joint perception during daily activities when appropriate patient selection is applied. Incorporating joint awareness–based measures such as the FJS may enhance the evaluation of surgical success beyond conventional clinical scores.