Medial compartment osteoarthritis (MCOA) of the knee is a common cause of knee pain and disability, particularly in ageing populations, though it also affects younger individuals with previous knee injuries or a genetic predisposition. The condition is characterised by degradation of the articular cartilage of the medial compartment, leading to pain, stiffness, swelling and reduced joint function. It accounts for a substantial proportion of knee arthroplasty procedures, and in many patients conservative measures such as physiotherapy, analgesia and weight management fail to control symptoms even in the early stages of disease.1 Surgical realignment by high tibial osteotomy (HTO) has emerged as an effective option for early-to-moderate MCOA, particularly in younger, active patients in whom joint preservation is a priority. HTO alters the alignment of the proximal tibia to redistribute weight-bearing forces away from the degenerated medial compartment, with the aim of relieving pain and delaying or avoiding total knee arthroplasty (TKA).2 Although the concept dates back to the early twentieth century, the technique has evolved considerably. In contrast to the traditional lateral closing wedge, the medial opening wedge technique creates a controlled gap in the medial proximal tibia to realign the limb, offering more precise control of correction with minimal soft-tissue disruption and bone loss.3 By offloading the medial compartment, the procedure reduces mechanical stress, decreases pain and improves function, allowing patients to remain active.4 Surgical success depends on several factors, including patient age, activity level, overall knee health and the degree of deformity; appropriate patient selection is therefore critical to outcome.5 The medial opening wedge technique has shown promising results in early-stage MCOA owing to its ability to achieve precise alignment, and the degree of correction can be tailored to the individual patient.6 Structured post-operative rehabilitation focusing on range of motion and quadriceps and hamstring strengthening is essential to recovery.7 While HTO carries potential risks such as infection, non-union and neurovascular injury, these are relatively uncommon and can be mitigated by careful technique and post-operative care; long-term studies report substantial and durable improvements in pain and knee function, with many patients avoiding arthroplasty for several years.8 Nonetheless, benefit depends on maintaining alignment over time, and ongoing follow-up is required as the joint continues to age.9,10 The present study analyses the effectiveness of the medial opening wedge HTO technique in patients with early medial compartment osteoarthritis of the knee, with particular attention to functional outcomes, pain relief, alignment correction and quality of life over a 12-month follow-up.

Study design and setting This prospective, observational, non-randomised, single-centre cohort study was conducted in the Department of Orthopaedics, Navodaya Medical College Hospital and Research Centre (NMCH&RC), Raichur, a tertiary-care teaching hospital equipped with modern diagnostic, surgical and rehabilitation facilities. Patients diagnosed with medial compartment osteoarthritis of the knee were assessed clinically, radiologically and functionally before and after surgery, and were followed for 12 months. Study duration The study was carried out over 12 months, from April 2023 to April 2024, comprising a pre-operative assessment phase, surgical intervention and structured post-operative follow-up. Patients were reviewed at 3, 6, 12, 18 and 24 months to document changes in clinical and radiological status; the 12-month review provided the primary functional endpoint reported here. Participants Inclusion criteria: (i) pain and disability due to osteoarthritis that interfered with high-demand employment or recreational activity; (ii) medial compartment osteoarthritis of the knee with varus deformity; (iii) age 30–65 years; (iv) ability to use crutches or a walker post-operatively; and (v) Kellgren–Lawrence grade 2 or 3 osteoarthritis of the knee. Exclusion criteria: (i) knee flexion less than 90°; (ii) flexion contracture greater than 15°; (iii) rheumatoid arthritis or other inflammatory joint disease; and (iv) uncontrolled systemic disease or infection likely to complicate surgery or rehabilitation. Sampling and sample size A consecutive sampling method was used; all patients meeting the eligibility criteria during the study period were invited to participate after providing informed consent. The sample size was calculated using the standard formula for a single proportion, assuming a prevalence (P) of medial compartment osteoarthritis of 0.04, an absolute allowable error (d) of 9% and a standard normal variate (Z) of 1.96, yielding a required sample of 20 patients. Study parameters and outcome measures Clinical parameters included pain, knee function and complications (such as infection or hardware failure). Radiological parameters comprised pre- and post-operative knee radiographs, including full-length alignment views. Pain was quantified using the Visual Analogue Scale (VAS). Functional outcome was assessed using three validated instruments — the International Knee Documentation Committee (IKDC) score, the Knee Injury and Osteoarthritis Outcome Score (KOOS) and the Knee Society Score (KSS), the latter reported separately as a knee score and a functional score. Radiological measurements were used to assess correction of the mechanical axis. Surgical technique All patients underwent medial opening wedge high tibial osteotomy under spinal or epidural anaesthesia. A longitudinal skin incision was made over the medial aspect of the proximal tibia, between the medial border of the patellar ligament and the posterior margin of the tibia. After subcutaneous dissection, the pes anserinus was retracted and the superficial fibres of the medial collateral ligament were released until the posteromedial cortex was exposed. Under fluoroscopic guidance, two parallel guide K-wires were passed from the medial cortex, approximately 4 cm below the joint line, towards the lateral cortex approximately 1 cm below the joint line. The osteotomy was completed with an oscillating saw along the guide wires, leaving the lateral cortical hinge intact, with care taken to complete the posteromedial cut. The osteotomy was gradually opened under valgus stress to the planned correction, and fixation was achieved with a locking HTO plate and metal spacer block secured with locking screws. Where the lateral hinge was compromised, supplementary cancellous screw fixation was used. The post-operative protocol comprised static quadriceps and ankle-pump exercises from day one, non-weight-bearing mobilisation for six weeks, partial weight bearing from six to twelve weeks, and full weight bearing thereafter, with follow-up at 3, 6, 12, 18 and 24 months. Statistical analysis Data were collected using structured case record forms and analysed using descriptive statistics, including means, standard deviations, frequencies and percentages. Associations between variables were assessed using odds ratios with 95% confidence intervals, and a P value less than 0.05 was considered statistically significant. Ethical considerations Ethical approval was obtained from the Institutional Ethics Committee of Navodaya Medical College Hospital and Research Centre, Raichur. Written informed consent was obtained from all participants. Confidentiality and anonymity were maintained throughout, and participants were free to withdraw at any time without affecting their care. The study was conducted in accordance with the principles of good clinical practice.

Twenty patients who satisfied the eligibility criteria were enrolled and completed the 12-month assessment. Demographic characteristics The cohort comprised 11 males (55%) and 9 females (45%). The majority of patients (55%) were aged 51–60 years, followed by 25% aged 31–40 years, 15% aged 41–50 years and 5% aged 61–65 years. The right knee was affected in 11 patients (55%) and the left in 9 (45%). Occupations reflected a physically active, weight-bearing population, with manual and standing occupations predominating. Table 1: Sex distribution Sex Frequency Percent Female 9 45 Male 11 55 Total 20 100 Table 2: Age distribution Age category (years) Frequency Percent 31–40 5 25 41–50 3 15 51–60 11 55 61–65 1 5 Total 20 100 Table 3: Side of knee involvement Side Frequency Percent Right 11 55 Left 9 45 Total 20 100 Table 4: Occupation of the patients Occupation Frequency Percent Housewife 4 20 Housemaid 2 10 Farmer 4 20 Butcher 1 5 Driver 3 15 Mechanic 2 10 Labourer 4 20 Total 20 100 Grade of osteoarthritis On the Kellgren–Lawrence classification, 15 patients (75%) had grade 2 osteoarthritis and 5 (25%) had grade 3, indicating that most patients presented with moderate degeneration — the stage best suited to a joint-preserving realignment procedure. Table 5: Grade of osteoarthritis (Kellgren–Lawrence) Grade of OA Frequency Percent Grade 1 0 0 Grade 2 15 75 Grade 3 5 25 Grade 4 0 0 Total 20 100 Radiological alignment Preoperatively all patients had a varus deformity ranging from 8° to 11°, most commonly 8° (45%). Following osteotomy, alignment was corrected to neutral or valgus in 18 patients (90%); the target correction of 2° valgus was achieved most frequently (40%). Residual varus of 1° and 4° was noted in one patient each, corresponding to the two cases of under-correction. Table 6: Preoperative deformity (varus alignment) Preoperative varus Frequency Percent 8° 9 45 9° 6 30 10° 4 20 11° 1 5 Total 20 100 Table 7: Postoperative deformity (alignment correction) Postoperative alignment Frequency Percent Valgus 3° 4 20 Valgus 2° 8 40 Valgus 1° 3 15 Neutral 3 15 Varus 1° 1 5 Varus 4° 1 5 Total 20 100 Pain (Visual Analogue Scale) Preoperatively, 13 patients (65%) reported severe pain and 7 (35%) moderate pain. Postoperatively, 16 patients (80%) were pain-free and the remaining 4 (20%) reported only mild pain, with no patient reporting moderate or severe pain. Table 8: Visual Analogue Scale – preoperative VAS category Frequency Percent No pain 0 0 Mild 0 0 Moderate 7 35 Severe 13 65 Total 20 100 Table 9: Visual Analogue Scale – postoperative VAS category Frequency Percent No pain 16 80 Mild 4 20 Moderate 0 0 Severe 0 0 Total 20 100 International Knee Documentation Committee (IKDC) score Preoperatively, 15 patients (75%) were rated ‘poor’ and 5 (25%) ‘fair’ on the IKDC. Postoperatively, outcomes improved to ‘excellent’ in 7 patients (35%), ‘good’ in 9 (45%) and ‘fair’ in 4 (20%), with no patient remaining in the ‘poor’ category. Table 10: Preoperative IKDC score IKDC (preoperative) Frequency Percent Poor 15 75 Fair 5 25 Good 0 0 Excellent 0 0 Total 20 100 Table 11: Postoperative IKDC score IKDC (postoperative) Frequency Percent Excellent 7 35 Good 9 45 Fair 4 20 Poor 0 0 Total 20 100 Knee Injury and Osteoarthritis Outcome Score (KOOS) Preoperatively, 12 patients (60%) were rated ‘poor’ and 8 (40%) ‘fair’ on the KOOS. Postoperatively, 14 patients (70%) achieved an ‘excellent’ rating and 6 (30%) a ‘good’ rating, with none remaining ‘fair’ or ‘poor’. Table 12: Preoperative KOOS score KOOS (preoperative) Frequency Percent Poor 12 60 Fair 8 40 Good 0 0 Excellent 0 0 Total 20 100 Table 13: Postoperative KOOS score KOOS (postoperative) Frequency Percent Excellent 14 70 Good 6 30 Fair 0 0 Poor 0 0 Total 20 100 Knee Society Score – knee score Preoperatively, 13 patients (65%) were rated ‘poor’ and 7 (35%) ‘fair’. Postoperatively, 14 patients (70%) achieved an ‘excellent’ knee score, 5 (25%) ‘good’ and 1 (5%) ‘fair’. Table 14: Preoperative Knee Society Score – knee score KSS knee (preoperative) Frequency Percent Poor 13 65 Fair 7 35 Good 0 0 Excellent 0 0 Total 20 100 Table 15: Postoperative Knee Society Score – knee score KSS knee (postoperative) Frequency Percent Excellent 14 70 Good 5 25 Fair 1 5 Poor 0 0 Total 20 100 Knee Society Score – functional score Preoperatively, 16 patients (80%) were rated ‘poor’ and 4 (20%) ‘fair’ on the functional score. Postoperatively, 16 patients (80%) achieved an ‘excellent’ functional score and 4 (20%) a ‘good’ score. Table 16: Preoperative Knee Society Score – functional score KSS functional (preoperative) Frequency Percent Poor 16 80 Fair 4 20 Good 0 0 Excellent 0 0 Total 20 100 Table 17: Postoperative Knee Society Score – functional score KSS functional (postoperative) Frequency Percent Excellent 16 80 Good 4 20 Fair 0 0 Poor 0 0 Total 20 100 Complications Complications were minor and self-limiting. Two patients developed superficial infection at the incision site, which resolved with regular dressings and antibiotics. Two patients sustained an intra-operative lateral hinge fracture, which was fixed with cancellous screws and progressed to union with good functional results. Two patients had under-correction of varus but nonetheless returned to their occupations with marked pain relief and reported satisfaction. One patient had implant prominence, managed conservatively with analgesics as removal was declined. No major complications, non-unions or surgical failures occurred. Table 18: Complications Complication Frequency Superficial infection at incision site 2 Intra-operative hinge fracture 2 Under-correction of varus 2 Implant prominence 1

This study evaluated the clinical, radiological and functional outcomes of medial opening wedge high tibial osteotomy in 20 patients with early medial compartment osteoarthritis of the knee. Across every outcome measure, the procedure produced substantial and consistent improvement, converting a uniformly impaired preoperative cohort into one with predominantly good-to-excellent function at 12 months while correcting varus malalignment to a mechanically favourable valgus position. The cohort showed a slight male predominance (55%), whereas some series have reported a female predominance — Singh et al. described a female-predominant cohort of 100 patients,11 and Kanoji et al. reported a male-to-female ratio of approximately 1:1.38.12 Such differences likely reflect variation in referral patterns and regional demographics rather than any gender-specific limitation of the procedure, as both sexes improved postoperatively. Most patients were aged 51–60 years, consistent with the typical demographic for MCOA. This is comparable with the mean ages reported by Ekeland et al. (47 years),13 Huda et al. (54.5 years)14 and Sreedhar et al. (approximately 50.8 years),15 and reinforces the role of joint preservation in the middle-aged, active patient in whom delaying arthroplasty is a priority. The predominance of Kellgren–Lawrence grade 2 disease (75%) indicates a cohort with moderate rather than end-stage degeneration, which is ideal for HTO. Ganeshsankar et al. and Habib and Khan similarly reported favourable functional gains in patients with moderate radiological degeneration,16,17 and Huda et al. documented significant improvement in patients selected at grades 2 and 3,14 supporting early intervention before advanced degeneration develops. Preoperative function was uniformly poor across all instruments, underscoring the disabling nature of MCOA. Comparable baseline deficits have been reported by Huda et al. and by Howells et al., the latter documenting severely compromised WOMAC and Knee Society scores that improved after osteotomy.14,18 Low baseline KOOS values in our cohort mirror those of Habib and Khan and Yadav et al.,17,19 while the poor preoperative Knee Society knee scores are consistent with the low mean scores reported by Ganeshsankar et al. and Sreedhar et al.15,16 Postoperatively, IKDC ratings shifted to predominantly ‘good’ and ‘excellent’, echoing the marked IKDC gains reported by Huda et al. and the functional improvement described by Howells et al.14,18 KOOS outcomes improved to 70% ‘excellent’, in agreement with Habib and Khan, who reported significant gains in activities of daily living after HTO.17 The near-universal improvement in KSS functional score (80% ‘excellent’) is consistent with the good-to-excellent outcomes reported by Sharma et al. and the significant functional gains reported by Kanoji et al.,20,12 both of whom, like the present series, observed only minor, conservatively managed complications. Correction of varus malalignment to a slight valgus is central to the mechanism of HTO, redistributing load away from the degenerated medial compartment. In our series, alignment improved from 8°–11° of varus to neutral or valgus in 90% of patients, comparable with the corrections to slight valgus reported by Singh et al. and others.11 This realignment not only relieves pain but may also slow further degeneration and postpone arthroplasty. The complication profile was favourable: superficial infection, hinge fracture, under-correction and implant prominence were all minor and managed without compromising outcome, and there were no non-unions or surgical failures. These findings are in keeping with the low complication rates reported in the contemporary literature and reinforce the safety of the medial opening wedge technique when performed with careful patient selection and meticulous surgical planning. The principal limitations of this study are its small sample size, single-centre design and relatively short 12-month primary follow-up, which preclude assessment of long-term survivorship and the durability of correction. Larger, multicentre studies with extended follow-up and comparison groups are warranted to confirm these findings and to define the long-term role of HTO relative to unicompartmental and total knee arthroplasty.

Medial opening wedge high tibial osteotomy is an effective, joint-preserving surgical treatment for early medial compartment osteoarthritis of the knee. In this prospective series it produced significant improvement in knee alignment, pain relief and function, with high patient satisfaction and low complication rates in appropriately selected patients. Early intervention in carefully selected, predominantly middle-aged patients can yield excellent functional results and may delay or avoid the need for total knee arthroplasty. HTO should therefore be strongly considered as a first-line surgical option in this patient group.

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