High tibial osteotomy for grey zone osteoarthritis: Anatomical correction or psychological challenge in return to sport?

We congratulate Pineda et al. [6] on their insightful study titled ‘Reliable pain and function outcomes but limited sport performance after high tibial osteotomy (HTO) for medial knee osteoarthritis (OA) in the grey zone between osteotomy and unicompartmental replacement’. The investigation focused on the ‘Grey Zone’ within the Alignment, Knee, Unicompartmental, Medial, and Arthroplasty (AKUMA) framework—a conceptual tool used to characterise deformity distribution and OA severity [5]. The ‘Grey Zone’ specifically refers to a clinically challenging demographic of patients with overlapping features of both intraarticular and extra-articular deformities, where either HTO or unicompartmental knee arthroplasty (UKA) could be considered appropriate [5]. This retrospective multicenter study evaluated 84 patients (aged 20–60 years) who underwent HTO between 2005 and 2015. With a mean follow-up of 8 years, the primary aim was to identify clinical and radiographic factors associated with success in pain, function and sport. The authors demonstrated that HTO provided reliable pain relief (72.0% WOMAC success) but revealed significant limitations in restoring high-level sports participation (6.8% Tegner success) [6]. As peers dedicated to knee preservation, we highly appreciate the authors' efforts in delineating the boundaries of surgical indications. Upon careful review, we believe several key factors warrant further discussion to understand why anatomical success did not translate into functional sports recovery. First, although Pineda et al. [6] evaluated the ‘perceived importance of sport’ as a motivational factor, it is essential to distinguish this from ‘psychological readiness’. While a patient may rate sport as ‘very important’, they may still experience significant psychological barriers. A systematic review indicated that despite physical recovery, ‘fear of reinjury’ and lack of psychological readiness remained primary barriers to returning to sport [2]. In the study by Pineda et al. [6], the mean age was 52.3 years, a demographic often characterised by avoidance behaviours established through chronic preoperative pain. To better elucidate why radiographic correction (improved medial proximal tibial angle) failed to enhance subjective outcomes, we recommend incorporating specific validated psychological scoring systems, such as the ACL-return to sport after injury (ACL-RSI) scale [7] or the psychological readiness to return to sport scale [1], both of which have shown utility in assessing the emotional transition back to athletic activity. Second, the body mass index (BMI) as a confounding factor may have been underestimated. The study reported a mean BMI of 28.9 ± 4.8 kg/m², approaching the threshold for obesity. A long-term follow-up study explicitly identified high BMI as an independent predictor of decreased long-term survival and conversion to arthroplasty following HTO [4]. For patients in the ‘Grey Zone’, where cartilage wear lies between indications for HTO and UKA, the mechanical stress of body weight on residual cartilage is likely more critical. Although OA grade was included in the multivariable regression, defining specific BMI ‘cut-offs’ for the Grey Zone may hold greater public health significance than radiographic grading alone for future patient selection. Furthermore, the criteria for ‘success’ merit reconsideration. Pineda et al. [6] defined success as a Tegner score ≥ 5, while acknowledging that this threshold was somewhat arbitrary. However, in previous literature, the strongest predictor for returning to sport was typically the preoperative sports level. Research by Faschingbauer et al. [3] demonstrated that preoperative activity level was the decisive factor in predicting postoperative return to sport; most patients recovered to or slightly below their preoperative level, but rarely exceeded it. If the median preoperative Tegner score in this cohort was inherently low, expecting a postoperative score ≥ 5 was unrealistic. Given the cohort's mean age, providing the rate of ‘return to pre-injury level’ would likely reflect the true efficacy of HTO in this subgroup more objectively than an absolute threshold. In conclusion, the study by Pineda et al. [6] suggests that for AKUMA Grey Zone patients, HTO currently functions more as a ‘pain-relieving’ procedure rather than a fully ‘sport-restoring’ one. Future research should shift from a purely biomechanical focus toward a biopsychosocial model. It is suggested that clinical practice incorporate preoperative psychological screening and rehabilitation plans that include psychological intervention for Grey Zone patients. We thank the authors again for their inspiring work, which provides valuable evidence-based medicine to refine the stepped-care strategy for knee preservation. Guanghao Chen: Conceptualisation; writing—original draft; supervision; writing—review and editing. Kunpeng Yang: Conceptualisation; writing—review and editing. ChatGPT (developed by OpenAI) was used solely to improve the language clarity and fluency of the manuscript. The tool was not involved in the study design, data analysis, or interpretation. The authors take full responsibility for the content and integrity of the work. The authors have no funding to report. The authors declare no conflicts of interest. The authors have nothing to report.