Abstract
Objectives
Medial opening-wedge high tibial osteotomy (MOWHTO) is a joint-preserving procedure designed to correct varus malalignment and reduce medial compartment overload in knee osteoarthritis (OA). Although historically reserved for early-stage disease, recent evidence suggests that patients with more advanced radiographic degeneration may still benefit from the procedure. However, the relationship between Kellgren–Lawrence (KL) grade and postoperative clinical outcomes remains controversial. This study aimed to evaluate early-term pain reduction and functional improvement following MOWHTO by comparing patients with low-grade OA (KL1–2) and moderate OA (KL3).
Methods
This retrospective observational study analyzed 73 consecutive adults who underwent standardized biplanar MOWHTO between May 2020 and May 2023 at a single tertiary center. Patients were stratified into KL1–2 (n=58) and KL3 (n=15) groups. Pain and function were assessed preoperatively and at 6, 12, and 24 months using the Visual Analog Scale (VAS), KOOS, and WOMAC index. Radiographic alignment parameters and complications were recorded.
Results
Preoperative VAS scores were high in both groups (KL1–2: 7.79±0.89; KL3: 8.27±0.70; p=0.066). At 24 months, VAS scores decreased significantly (KL1–2: 3.33±1.15; KL3: 1.87±0.74), with KL3 patients exhibiting greater pain reduction (ΔVAS: 6.40±1.06 vs. 4.47±1.52; p<0.001). KOOS scores improved substantially in both groups (KL1–2: 53.1±8.2 to 85.4±5.8; KL3: 43.9±7.6 to 76.7±6.3), with similar functional gains (ΔKOOS: 32.3±6.0 vs. 32.8±8.9; p=0.85). WOMAC scores improved significantly (KL1–2: 51.9±3.6 to 30.8±7.1; KL3: 61.4±4.3 to 34.9±5.6), with greater improvement in KL3 (ΔWOMAC: 26.5±8.2 vs. 21.2±7.4; p=0.034). The overall complication rate requiring surgery was 12.3%, and 24-month arthroplasty-free survival was 96.0%.
Conclusion
MOWHTO provides meaningful early-term improvements in pain and function across all KL grades. Despite worse baseline status, KL3 patients achieved comparable or greater symptomatic relief. These findings support MOWHTO as a viable option for carefully selected patients with moderate OA seeking to delay arthroplasty.
Keywords: High Tibial Osteotomy, osteoarthritis knee, pain measurement, treatment outcome
Osteoarthritis (OA) is the most common degenerative joint disorder, characterized by progressive loss of articular cartilage, osteophyte formation, and synovial proliferation, ultimately leading to pain and functional limitation.[1-3] In the knee, varus malalignment frequently increases medial compartment loading, thereby accelerating degenerative processes.[4-6] While total knee arthroplasty (TKA) remains the standard surgical treatment for advanced OA, it is less suitable for younger and more active individuals. Medial opening-wedge high tibial osteotomy (MOWHTO) is a joint-preserving procedure that corrects varus malalignment and redistributes mechanical load toward the lateral compartment, thereby improving pain and function.[4,5,7]
Recent literature has expanded the indications for MOWHTO to include patients with more advanced OA. Multiple studies have reported favorable outcomes in terms of pain relief, functional recovery, and survivorship, even in cases with severe radiographic degeneration.[8-13] Despite these encouraging findings, controversy persists regarding prognostic factors that influence postoperative outcomes, particularly in patients with higher Kellgren–Lawrence (KL) grades. Understanding the relationship between radiographic OA severity and postoperative clinical outcomes is critical for surgical decision-making.
Therefore, this study aimed to evaluate the early-term clinical outcomes of patients undergoing MOWHTO, stratified according to the Kellgren–Lawrence classification. Special emphasis was placed on patients with KL grade 3 to determine the extent of postoperative pain reduction and functional improvement. Our research question was as follows: among adult patients with varus knee deformity and medial compartment osteoarthritis undergoing medial opening-wedge high tibial osteotomy, do those with KL-3 disease achieve comparable two-year improvements in patient-reported outcomes, including pain and functional scores, compared with patients classified as KL-1 or KL-2? Based on the existing literature, we hypothesized that MOWHTO is an effective treatment even for patients with KL-3 disease, providing meaningful early clinical improvement.
Methods
This retrospective observational study was approved by the University of Health Sciences, Şişli Hamidiye Etfal Training and Research Hospital ethics committee (decision number: 3028; approval date: May 30, 2025) and conducted in accordance with the principles of the Declaration of Helsinki. Prospectively collected clinical data from patients who underwent medial opening-wedge high tibial osteotomy (MOWHTO) were analyzed retrospectively. Patients were stratified into two groups based on radiographic OA severity: low-grade OA, KL 1+KL 2, versus moderate OA, KL 3. This classification enabled evaluation of the influence of OA severity on postoperative functional recovery following MOWHTO.
Between May 2020 and May 2023, 73 consecutive adult patients who underwent medial MOWHTO for symptomatic medial compartment osteoarthritis at a single tertiary orthopedic center were included. The inclusion criteria were medial compartment osteoarthritis with varus malalignment, mechanical axis deviation (MAD)>20%, availability of functional outcome assessments at predefined time points (preoperatively and at 6, 12, and 24 months), a minimum 24-month clinical follow-up, undergoing medial opening-wedge HTO, and radiographic Kellgren–Lawrence (KL) grade 1–3 recorded on preoperative standing radiographs. The exclusion criteria were preoperative coronal plane deformity>15°, prior ipsilateral knee surgery or major concomitant deformity of the same extremity, missing clinical data or incomplete follow-up, need for double-level osteotomy or external fixation, and preoperative knee flexion<90° or extension lag>5°. All consecutive patients meeting the criteria were included, with no exclusions applied, thereby minimizing selection bias.
Preoperative evaluation included standing anteroposterior and lateral knee radiographs and full-length weight-bearing orthoroentgenograms. KL grading was independently performed by two orthopedic surgeons blinded to clinical outcomes. Interobserver reliability analysis using Cohen’s kappa demonstrated good agreement (κ=0.87). Postoperative radiological measurements included MAD, medial proximal tibial angle (MPTA), and mechanical MPTA (mMPTA). These parameters were recorded on standardized full-length radiographs to verify correction magnitude and implant positioning. Lateral hinge fractures were retrospectively classified according to the Takeuchi classification using immediate postoperative radiographs.
All operations were performed by the same orthopedic team using a standardized biplanar medial opening-wedge HTO technique with preservation of the lateral cortex. Surgical planning employed the Miniaci method targeting the Fujisawa point. Fixation was achieved with a TRUE LOCK Proximal Tibia High Osteotomy Plate (TRUEMED, Istanbul, Türkiye). No allograft or bone substitute was used in any patient. Toe-touch weight-bearing was permitted immediately, followed by progressive weight-bearing after 6 weeks upon radiographic confirmation of early healing. Range-of-motion exercises began postoperatively, and supervised physiotherapy was provided as needed.
Functional status was evaluated using validated patient-reported outcome measures (PROMs), including the Visual Analog Scale (VAS) for pain, Knee Injury and Osteoarthritis Outcome Score (KOOS) (symptoms, daily activities, and quality of life), and WOMAC index. Assessments were conducted preoperatively and at 6, 12, and 24 months postoperatively during routine outpatient visits.
Statistical Analysis
All statistical analyses were performed using standard statistical software. Continuous variables were tested for normality using the Shapiro–Wilk test. Descriptive statistics were reported as mean±standard deviation (SD) or median with interquartile range (IQR), depending on data distribution. Categorical variables were summarized as frequencies and percentages. Between-group comparisons (KL 1–2 vs. KL 3) were performed using the independent-samples t-test or Mann–Whitney U test for continuous variables and the chi-square or Fisher’s exact test for categorical variables. Repeated measures of functional scores (VAS, KOOS, and WOMAC) across follow-up intervals (preoperative and 6, 12, and 24 months) were analyzed using repeated-measures ANOVA or the Friedman test with Bonferroni-adjusted post hoc comparisons. Effect sizes (Cohen’s d or η2) were calculated to evaluate clinical relevance. A p-value<0.05 was considered statistically significant. Missing data were handled using complete-case analysis, as missingness was minimal and random. Survival analyses were performed using the Kaplan–Meier method to estimate arthroplasty-free and reoperation-free survival. Time zero was defined as the date of the index surgery. Events were defined as conversion to arthroplasty for arthroplasty-free survival and any subsequent ipsilateral reoperation for reoperation-free survival. Patients without an event were censored at the date of last clinical follow-up. Survival curves were compared between groups using the log-rank test.
Results
A total of 73 knees in 73 patients were included in the final analysis. The distribution of radiographic severity according to the KL classification was as follows: KL 1, 24 (32.9%); KL 2, 34 (46.6%); and KL 3, 15 (20.5%). Accordingly, 58 patients (79.5%) were classified as the low-grade OA group (KL 1–2), and 15 patients (20.5%) were classified as the moderate OA group (KL 3). The mean age was 47.2±9.6 years in the KL 1–2 group and 57.9±3.7 years in the KL 3 group, indicating that patients with KL 3 osteoarthritis were older on average. The sex distribution and side of surgery were comparable between the groups (Table 1).
Table 1.
Baseline Demographic and Clinical Characteristics of the Study Population Stratified by KL Grade
| Characteristic | Total n=73 | Group 1(KL1-2) n=58 | Group 2(KL3) n=15 | p |
|---|---|---|---|---|
| Age (years), Mean±SD | 49.43±9.72 | 47.24±9.6 | 57.9±3.67 | 0.001b |
| BMI (kg/m2), Mean±SD | 27.4±2.1 | 27.38±2.01 | 27.95±2.19 | 0.372b |
| Follow-up duration (month), Mean±SD | 28.10±3.12 | 27.95±3.27 | 27.40±2.66 | 0.503 |
| Gender, n (%) | ||||
| Female | 34 (47) | 28 (48) | 6 (40) | 0.567a |
| Male | 39 (53) | 30 (52) | 9 (60) | |
| Side, n (%) | ||||
| Left (L) | 36 (49) | 27 (47) | 9 (60) | 0.523a |
| Right (R) | 37 (51) | 31 (53) | 6 (40) | |
| Smoking, n (%) | ||||
| Yes | 44 (60) | 35 (60) | 10 (66) | 0.936a |
| No | 29 (40) | 23 (40) | 5 (34) |
a = Pearson chi-square test, b = independent-samples t-test. This table presents the baseline demographic and clinical characteristics of the 73 patients included in the study, divided into two groups according to the Kellgren–Lawrence (KL) grading system. Continuous variables are expressed as mean±standard deviation, while categorical variables are presented as numbers and percentages. Group comparisons were performed using the independent samples t-test (b) for continuous variables and the Pearson Chi-square test (a) for categorical variables. A p-value <0.05 was considered statistically significant.
Preoperatively, mean VAS scores were high in both groups, at 7.79±0.89 in the KL 1–2 group and 8.27±0.70 in the KL 3 group, with no statistically significant difference between the groups (Mann–Whitney U, p≈0.066). At 24 months, VAS scores decreased significantly in both groups (KL 1–2: 3.33±1.15 vs. KL 3: 1.87±0.74). Within-group analysis showed a significant reduction in pain from baseline to 24 months in both KL 1–2 (Wilcoxon, p<0.001) and KL 3 patients (Wilcoxon, p<0.001). The mean pain reduction (ΔVAS=preoperative−24 months) was 4.47±1.52 in the KL 1–2 group and 6.40±1.06 in the KL 3 group. This difference in ΔVAS between the groups was statistically significant, indicating greater pain reduction in KL 3 patients (Mann–Whitney U, p<0.001) (Table 2, 3 and 4).
Table 2.
Comparison of KOOS, WOMAC, and VAS scores between KL grade groups at baseline and postoperative follow-ups
| Clinical score name / follow ups (months) | Group1 (KL1-2) n=58 Mean±SD | Group 2 (KL 3) n=15 Mean±SD | p |
|---|---|---|---|
| KOOS-BT | 53.09±8.23 | 43.93±7.63 | p=0.005 t |
| KOOS-6. | 53.84±8.14 | 44.00±7.56 | p=0.03 t |
| KOOS-12. | 85.00±6.70 | 76.73±6.26 | p=0.03 t |
| KOOS-24. | 85.4±5.8 | 76.7±6.3 | p=0.19t |
| ΔKOOS (KOOS 24.-KOOS BT) | 32.3±6.0 | 32.8±8.9 | p=0,85t |
| WOMAC-BT | 51.95±3.64 | 61.40± 4.25 | p=0.01 t |
| WOMAC-6. | 51.62±4.42 | 61.20±3.91 | p=0.01 t |
| WOMAC-12 | 31.50±5.84 | 35.40±5.84 | p=0.01 t |
| WOMAC-24 | 30.78±7.05 | 34.93±3.63 | p=0.038 t |
| ΔWOMAC(WOMAC 24.-WOMAC BT) | 21.2±7.4 | 26.5±8.2 | p=0,034 t |
| VAS-BT | 7.79±0.89 | 8.27±0.70 | p=0.061MWU |
| VAS-6. | 7.48±0.96 | 8.53±0.64 | p=0. 001 MWU |
| VAS-12. | 3.50±0.82 | 2.20±0.56 | p=0. 001 MWU |
| VAS-24. | 3.33±1.15 | 1.87±0.74 | p=0.001 MWU |
| ΔVAS (VAS 24.-VAS BT) | 4.47±1.5 | 6.40±1.0 | p< 0.001MWU |
t: Independent samples t-test , MWU: Mann–Whitney U, SD: Standart Deviation; Values are presented as mean±standard deviation. Between-group comparisons (KL 1–2 vs. KL 3) were performed using the Mann–Whitney U test for non-parametric variables and the independent samples t-test for normally distributed variables. A p-value <0.05 was considered statistically significant.
Table 3.
Within-group comparison of pre-treatment and postoperative WOMAC, KOOS, and VAS scores in patients with KL 1–2 osteoarthritis
| Group 1 | p | ||
|---|---|---|---|
| BT n=58 Mean±SD | 6. months n=58 Mean±SD | ||
| WOMAC | 51.95±3.64 | 51.62±4.42 | 0.350pt |
| KOOS | 53.09±8.23 | 53.84±8.14 | 0.116pt |
| VAS | 7.79±0.89 | 7.48±0.96 | 0.019W |
| BT n=58 Mean±SD | 12. months n=58 Mean±SD | ||
| WOMAC | 51.95±3.64 | 31.50±5.84 | 0.001pt |
| KOOS | 53.09±8.23 | 85.00±6.70 | 0.001pt |
| VAS | 7.79±0.89 | 3.50±0.82 | 0.001w |
| BT n=58 Mean±SD | 24. months n=58 Mean±SD | ||
| WOMAC | 51.95±3.64 | 30.78±7.05 | 0.001pt |
| KOOS | 53.09±8.23 | 85.4±5.8 | 0.001pt |
| VAS | 7.79±0.89 | 3.33±1.15 | 0.001w |
| 6.ay n=58 Mean±SD | 12. months n=58 Mean±SD | ||
| WOMAC | 51.62±4.42 | 31.50±5.84 | 0.001pt |
| KOOS | 53.84±8.14 | 85.00±6.70 | 0.001pt |
| VAS | 7.48±0.96 | 3.50±0.82 | 0.001w |
| 6.ay n=58 Mean±SD | 24. months n=58 Mean±SD | ||
| WOMAC | 51.62±4.42 | 30.78±7.05 | 0.001pt |
| KOOS | 53.84±8.14 | 85.4±5.8 | 0.001pt |
| VAS | 7.48±0.96 | 3.33±1.15 | 0.001w |
| 12.ay n=58 Mean±SD | 24. months n=58 Mean±SD | ||
| WOMAC | 31.50±5.84 | 30.78±7.05 | 0.086pt |
| KOOS | 85.00±6.70 | 85.4±5.8 | 0.260pt |
| VAS | 3.50±0.82 | 3.33±1.15 | 0.255w |
Values are presented as mean±standard deviation. Within-group changes between time points were analyzed using paired t-tests (PT) for normally distributed variables and the Wilcoxon signed-rank test (W) for non-parametric variables. BT: Baseline. A p-value <0.05 was considered statistically significant.
Table 4.
Within-group comparison of pre-treatment and postoperative WOMAC, KOOS, and VAS scores in patients with KL 3 osteoarthritis
| Group 2 | p | ||
|---|---|---|---|
| BT n=15 Mean±SD | 6. months n=15 Mean±SD | ||
| WOMAC | 61.40±4.25 | 61.20±3.91 | 0.458pt |
| KOOS | 43.93±7.63 | 44.00±7.56 | 0.334pt |
| VAS | 8.27±0.70 | 8.53±0.64 | 0.041w |
| BT n=15 Mean±SD | 12. months n=15 Mean±SD | ||
| WOMAC | 61.40±4.25 | 35.40±5.84 | 0.001pt |
| KOOS | 43.93±7.63 | 76.73±6.26 | 0.001pt |
| VAS | 8.27±0.70 | 2.20±0.56 | 0.001w |
| BT n=15 Mean±SD | 24. months n=78 Mean±SD | ||
| WOMAC | 61.40±4.25 | 34.93±3.63 | 0.001pt |
| KOOS | 43.93±7.63 | 76.7±6.3 | 0.001pt |
| VAS | 8.27±0.70 | 1.87±0.74 | 0.001w |
| 6. months n=15 Mean±SD | 12. months n=15 Mean±SD | ||
| WOMAC | 61.20±3.91 | 35.40±5.84 | 0.001pt |
| KOOS | 44.00±7.56 | 76.73±6.26 | 0.001pt |
| VAS | 8.53±0.64 | 2.20±0.56 | 0.001w |
| 6. months n=15 Mean±SD | 24. month n=15 Mean ± SD | ||
| WOMAC | 61.20±3.91 | 34.93±3.63 | 0.001pt |
| KOOS | 44.00±7.56 | 76.7±6.3 | 0.001pt |
| VAS | 8.53±0.64 | 1.87±0.74 | 0.001w |
| 12. months n=15 Mean±SD | 24. months n=15 Mean±SD | ||
| WOMAC | 35.40±5.84 | 34.93±3.63 | 0.388pt |
| KOOS | 76.73±6.26 | 76.7±6.3 | 0.165pt |
| VAS | 2.20±0.56 | 1.87±0.74 | 0.173w |
Values are presented as mean±standard deviation. Within-group changes across follow-up periods were analyzed using paired t-tests for normally distributed variables and the Wilcoxon signed-rank test for non-parametric variables. BT: Baseline. A p-value <0.05 was considered statistically significant.
Preoperative KOOS scores were substantially lower in the KL 3 group than in the KL 1–2 group (43.9±7.6 vs. 53.1±8.2), reflecting poorer baseline functional status in patients with more advanced osteoarthritis. At 24 months, KOOS scores improved markedly in both groups, reaching 85.4±5.8 in KL 1–2 patients and 76.7±6.3 in KL 3 patients. Within-group analysis demonstrated a statistically significant increase in KOOS scores from baseline to two years in both KL 1–2 and KL 3 patients (paired t-test, p<0.001 for both). The magnitude of improvement (ΔKOOS) was similar between the groups, measuring 32.3±6.0 in KL 1–2 patients and 32.8±8.9 in KL 3 patients, with no significant between-group difference (p≈0.85). These findings indicate that although patients with KL 3 osteoarthritis had worse initial function and lower absolute postoperative KOOS scores, their relative functional gains following MOWHTO were comparable to those achieved by KL 1–2 patients (Table 2, 3 and 4).
At baseline, WOMAC scores—reflecting pain, stiffness, and functional limitation—were considerably worse in the KL 3 group than in the KL 1–2 group (61.4±4.3 vs. 51.9±3.6; p<0.001), indicating greater disability before surgery. By 24 months, substantial improvements were observed in both groups, with WOMAC scores decreasing to 30.8±7.1 in the KL 1–2 group and 34.9±5.6 in the KL 3 group. Within-group comparisons demonstrated statistically significant improvements from baseline to 24 months in both groups (paired t-test, p<0.001 for each). When evaluating the degree of improvement (ΔWOMAC), KL 3 patients exhibited a significantly greater reduction in disability, with an average improvement of 26.5±8.2 compared with 21.2±7.4 in KL 1–2 patients (p≈0.034). This indicates that although KL 3 patients began with worse functional status, they achieved more pronounced symptomatic and functional recovery following MOWHTO (Table 2, 3 and 4).
Complications and Reoperations
Postoperative complications requiring surgical intervention occurred in nine patients (12.3%). These included conversion to knee arthroplasty in three patients, acute fixation revision due to loss of reduction in one patient, and secondary realignment with external fixation at two years in one patient. Four patients required operative debridement for infection or wound-related complications.
Lateral hinge fractures were observed in 15 patients (20.5%). According to the Takeuchi classification, 12 fractures were classified as Type I and three as Type II, whereas no Type III fractures were identified. None of the lateral hinge fractures progressed to nonunion, implant failure, or loss of correction during follow-up. All infectious complications were successfully treated without necessitating hardware removal. The 24-month arthroplasty-free survival rate was 96.0% (95% CI: 90.2–100), demonstrating stable survival throughout the first postoperative year and a mild decline thereafter. When all reoperation events were combined into a composite endpoint (arthroplasty, fixation revision, secondary realignment, or operative debridement), the reoperation-free survival rate at 24 months was 91.3% (95% CI: 84.1–98.5). Survival rates exceeded 95% across all KL groups at 12 months, and no early catastrophic failures were observed. Moreover, survival curves did not differ significantly among KL grades 1–3 (log-rank p=0.41 for arthroplasty-free survival; p=0.38 for reoperation-free survival) (Fig. 1 and 2).
Figure 1.
Kaplan–Meier Curve of Arthroplasty-Free Survival Over 24 Months.
The Kaplan–Meier survival curve demonstrates arthroplasty-free survival in the study cohort over a 24-month postoperative period. Survival remained high throughout follow-up, with a final arthroplasty-free survival rate of 96%. No significant difference was observed among KL grades (log-rank p=0.41).
Figure 2.
Kaplan–Meier Curve of Reoperation-Free Survival Over 24 Months.
The Kaplan–Meier survival curve illustrates reoperation-free survival over the 24-month postoperative period. The overall reoperation-free survival rate was 91.3% at final follow-up. No significant differences were detected among KL grades (log-rank p=0.38), indicating comparable reoperation risk across radiographic severity levels.
Discussion
The most important finding of this study is that medial opening-wedge high tibial osteotomy (MOWHTO) provides substantial and clinically meaningful improvements in both pain and function during the first postoperative year and that these gains are maintained through 24 months across all Kellgren–Lawrence (KL) grades. Consistent with our hypothesis, pain reduction and functional recovery progressed most rapidly during the first 12 months, after which outcomes plateaued. Despite significant differences in baseline severity, KL grade did not meaningfully influence the magnitude of improvement, highlighting that even patients with more advanced medial compartment osteoarthritis can benefit from MOWHTO.
A large body of research has established lower extremity malalignment as a key contributor to medial compartment overload, disease progression, and worsening symptoms in knee osteoarthritis.[14–17] In our study, both KL 1–2 and KL 3 patients demonstrated marked reductions in VAS scores, with significantly greater absolute pain reduction in KL 3 patients by 24 months. These results align with previous reports indicating that realignment procedures, by offloading the medial compartment, yield rapid and durable symptomatic improvement.[1,2] The temporal pattern in our cohort, showing steep improvement followed by stabilization, mirrors findings from earlier postoperative recovery studies.[14,18-20]
Functional outcomes followed a similar trajectory. Although patients with KL grade 3 osteoarthritis exhibited lower KOOS and WOMAC scores preoperatively and at 24 months, the magnitude of improvement over time was comparable to that observed in KL 1–2 patients. This suggests that while radiographic severity affects absolute function, it does not prevent meaningful postoperative gains. These observations are supported by studies showing that appropriately selected patients with advanced OA can still achieve clinically relevant improvement following HTO.[21-23] The mean age of our cohort (49.4 years) was lower than that reported in many East Asian studies, in which patients in their 60s demonstrated significant functional gains within one year.[22] Taken together, these findings reinforce the view that neither chronological age nor KL grade alone should be considered a strict contraindication to MOWHTO; rather, patient selection should integrate alignment, activity level, and cartilage status. Although patients in the KL 3 group were significantly older than those in the KL 1–2 group, age itself may independently influence postoperative recovery and functional improvement. However, our primary analyses focused on changes from baseline (delta scores), which partially reduce the potential impact of baseline age-related differences. Nevertheless, the possible confounding effect of age should be considered when interpreting the findings.
Historical long-term studies, such as the seminal 20-year report by Hernigou, revealed diminishing survivorship of HTO over time, with only 12 knees achieving durable pain-free function following the initial osteotomy.[24] Given the relatively short follow-up of our study, the high functional scores observed at 12 and 24 months are consistent with expectations. However, the early plateau in outcomes, even during mid-term follow-up, suggests that longer-term studies stratified by KL grade may offer insights into whether disease severity predicts late failures, the need for secondary procedures, or differential survivorship.
Studies evaluating return to work after HTO report a recovery window ranging from 9 to 16 weeks.[25-27] In our cohort, no significant improvement was noted at the 6-month postoperative assessment; however, both pain and functional scores improved sharply between months 6 and 12. Between 12 and 24 months, scores fluctuated modestly (26 worsened, 32 improved, and 15 remained stable), but none of these changes reached statistical significance. Notably, most decreases occurred in KL 3 patients, suggesting that outcomes in more advanced OA should be interpreted with caution and that preoperative counseling should reflect this variability.
Prior literature presents mixed conclusions regarding MOWHTO in advanced-stage osteoarthritis. Some authors caution that extensive radiographic degeneration may limit long-term success or reduce the durability of correction. For example, Ayet et al. [28] demonstrated favorable 10-year survivorship of MOWHTO but largely excluded severe OA, limiting the applicability of their findings to KL 3 patients. Conversely, Goshima et al.[21] reported that neither age nor KL grade should serve as an absolute contraindication when patient selection is carefully performed. Our subgroup analysis supports this more permissive viewpoint: although KL 3 patients had lower baseline and postoperative WOMAC and KOOS scores, they continued to demonstrate significant improvements from their preoperative status. Similar conclusions have been drawn in multicenter prospective studies from Japan and Canada, showing the potential for meaningful improvement even in bicompartmental or advanced OA cases, albeit with caution against routine use in severely degenerated joints.[18,23]
These findings have important implications for surgical decision-making. Although patients with lower KL grades tend to achieve better absolute outcomes, those with advanced OA should not be categorically excluded from MOWHTO. Younger or active KL 3 patients who are not yet candidates for knee arthroplasty may still derive meaningful benefit when alignment correction is adequate and expectations are appropriately managed. The significant pain relief and functional gains observed in KL 3 patients in this study underscore the importance of individualized assessment rather than reliance solely on radiographic criteria.
Lateral hinge fracture is a recognized intraoperative complication of medial opening-wedge high tibial osteotomy and has been reported in approximately 15%–30% of cases in previous studies.[22] In the present cohort, lateral hinge fractures occurred in 15 knees (20.5%), which is consistent with the published literature. According to the Takeuchi classification, 12 fractures were Type I and three were Type II, whereas no Type III fractures were identified. Importantly, none of these fractures resulted in nonunion, implant failure, or loss of correction during follow-up, suggesting that the standardized surgical technique provided adequate construct stability despite the occurrence of lateral hinge fractures.
A major strength of this study is the relatively homogeneous cohort treated with a standardized surgical technique performed by the same orthopedic team using a consistent implant platform. The prospective acquisition of PROMs at multiple postoperative intervals and a minimum follow-up of 24 months enhance internal validity. The KL-based subgroup analysis also provides valuable insight into differential recovery patterns. However, several limitations must be acknowledged. The KL classification, although widely used, does not capture cartilage or meniscal pathology, which may influence outcomes. Additionally, the lack of a control group (e.g., nonoperative or arthroplasty cohorts) limits comparative interpretation. Furthermore, this was a single-center study in which all procedures were performed by the same experienced surgical team. Although this ensured a standardized surgical technique and postoperative protocol, it may limit the external generalizability of our findings to other institutions and surgeons. Finally, the follow-up period, while adequate for early-term outcomes, does not provide information on longer-term survivorship or potential late failure of the osteotomy.
Conclusion
Medial opening-wedge high tibial osteotomy (MOWHTO) yields substantial early- to mid-term improvements in pain and function across all KL grades. While patients with less severe radiographic disease achieve higher absolute scores, those with KL grade 3 osteoarthritis also experience clinically meaningful benefits. These findings support the role of MOWHTO as a viable joint-preserving treatment option, particularly in appropriately selected patients who are younger, active, or seeking to postpone arthroplasty. Future long-term studies stratified by OA severity are needed to clarify durability and late outcomes.
Acknowledgments
The authors thank the clinical staff of the Orthopaedics and Traumatology Department at Istanbul Sisli Hamidiye Etfal Training and Research Hospital for their assistance during data collection.
Footnotes
Please cite this article as ”Altuntas Y, Ipek E, Armagan R, Alibakan G, Demirkale I, Eren OT. Medial Opening-Wedge High Tibial Osteotomy Delivers Meaningful Early Outcomes Even in KL-3 Osteoarthritis: A 24-Month Stratified Cohort Analysis. Med Bull Sisli Etfal Hosp 2026;60(3):304-312”.
Disclosures
Ethics Approval
Ethics committee approval for this study was obtained from the University of Health Science, Sisli Hamidiye Etfal Training and Research Hospital (Approval no: 3028; date: May 30, 2025)
Informed Consent
Informed consent was obtained from all patients involved in this study.
Conflict of Interest
The authors declare that there is no conflict of interest.
Financial Disclosure
This study received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
Use of AI for Writing Assistance
No artificial intelligence-assisted technologies were used in the conduct of this study, data analysis, or manuscript preparation.
Authorship Contributions
Concept – Y.A., I.D., E.I., O.T.E.; Design – Y.A., E.I., G.A., I.D.; Supervision – I.D., O.T.E.; Materials – Y.A., E.I., R.A.; Data collection &/or processing – Y.A., E.I., R.A.; Analysis and/or interpretation – Y.A., E.I., R.A., G.A., I.D., O.T.E.; Literature search – Y.A.; Writing – Y.A.; Critical review – E.I., R.A., G.A., I.D., O.T.E., Y.A.
Peer-review
Externally peer-reviewed.
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