Background Medial compartment osteoarthritis of the knee remains one of the most prevalent and disabling joint disorders, particularly in younger, active patients. High tibial osteotomy (HTO) is an established joint-preserving surgical procedure that redistributes the mechanical axis to unload the diseased medial compartment, thereby relieving pain and slowing arthritic progression. Despite its widespread use, data on functional and radiological outcomes in Indian patients under 60 years of age remain limited. This study aimed to evaluate the functional and radiological outcomes of medial open-wedge HTO in younger patients with medial compartment osteoarthritis at a tertiary care centre in Mandya, Karnataka. Methods A retrospective observational study was conducted on 30 patients with isolated medial compartment osteoarthritis treated with high tibial osteotomy at Mandya Institute of Medical Sciences. Inclusion criteria required patients to be under 60 years of age with isolated medial compartment osteoarthritis, adequate preoperative range of motion, and written informed consent. Functional outcomes were assessed using the Knee Society Score (KSS) and the Knee Injury and Osteoarthritis Outcome Score (KOOS) at 6 weeks, 3 months, and 6 months postoperatively. Radiological assessment included mechanical axis deviation, medial proximal tibial angle (MPTA), joint space width, and posterior tibial slope on weight-bearing long-cassette radiographs. Results The study included 23 males and 7 females with a mean age of 51.4 ± 5.6 years and a mean follow-up of 6 months. Postoperatively, 80% (n=24) of patients achieved excellent results and 13.3% (n=4) achieved good results by KSS. The mean preoperative KSS Knee Score improved from 51.8 ± 7.9 points to 79.4 ± 6.8 points, and the mean Functional Score improved from 54.2 ± 9.1 to 81.6 ± 8.0 points (both p<0.001). Pain relief was marked: 90% of patients had moderate or severe preoperative pain, while 86.7% reported only mild pain or no pain at final follow-up. Knee flexion greater than 100 degrees was achieved in 73.3% of patients postoperatively compared to 40% preoperatively. Radiological correction to the planned mechanical axis target was satisfactory in 86.7% of cases. Five complications were recorded: three wound infections and two deep vein thromboses, all managed conservatively without the need for surgical revision.

High Tibial Osteotomy, Medial Compartment Osteoarthritis, Knee, Varus Deformity, Functional Outcomes, KOOS, Knee Society Score, joint preservation, younger patients