Treatment of younger patients with medial unicompartmental disease of the knee joint remains a challenging therapeutic dilemma. With the refinement of implant design, fixation and the minimally invasive techniques employed with unicompartmental knee replacement, indications have expanded to include its use in young patients. A prospective cohort of 46 unicompartmental knee procedures were performed with a 2-year minimum and 6-year maximum follow-up, using the Oxford phase III unicompartmental knee arthroplasty, in the younger patient group (age 60 or younger). We conclude that the unicompartmental knee arthroplasty is an important option for the treatment of medial compartment disease for patients 60 years or younger. Obesity can cause technical difficulties, increased risk of complications and early failure of this prosthesis.