Twenty-seven patients (28 knees), with a median age of 42 (27-50) years treated with a high tibial osteotomy for early medial gonarthrosis (Ahlbäck's Stage I) were examined after 11 (7-18) years. Twenty-four were men; 18 knees had had previous meniscus and ligament lesions. At follow-up, 22 knees were satisfactory and 9 patients managed high-activity sports or heavy work. In 25/28 knees, the arthrotic process had not progressed radiographically.