Opening wedge high tibial osteotomy (OWHTO) is a treatment option for medial compartment osteoarthritis of the knee in the young active adult. Limited evidence exists in the literature regarding return to activities following OWHTO. We performed a retrospective study of local patients who underwent OWHTO from 2005 – 2012 assessing post-operative return to sporting function. Patients with additional knee pathology, surgery or alternative issues affecting activity were excluded. 110 patients met inclusion criteria, 75 were successfully contacted. Mean improvement in pain score = 4.8/10 (95%CI 4.2 to 5.4, p<0.01). Mean pre-operative KOS-SAS score = 0.5/2, mean post-operative KOS-SAS score = 1.1/2, mean change in KOS-SAS score following OWHTO = 0.6 (95% CI 0.5 to 0.7, p<0.01). Mean pre-morbid Tegner score = 5.9/10, pre-operative = 2.7/10, post-operative = 4.2/10. Mean change in Tegner score following OWHTO = 1.5 (95% CI 1 to 1.9, p<0.01). Following OWHTO 25% of patients achieved pre-morbid Tegner scores. Patient BMI, age, type of implant or graft used had no significant effect on outcome. OWHTO can temporarily improve pain, activity and sporting levels in young patients with isolated medial compartment knee OA. Return to pre-morbid activity levels and even high level sports function is possible although not the norm.