Inclusion Criteria:  Symptomatic medial unicompartment knee arthritis Active patients younger than 55 years Good range of motion (ROM) . Intact lateral compartment  Exclusion Criteria:  Combined medial and lateral arthrosis. Markedly decreased knee range of motion (arc of motion 10°). Ligamentous instability. Severe joint destruction (≥Ahlback grade III). ≥55 years of age. Advanced patellofemoral arthritis. Rheumatoid arthritis. Structural lower extremity deformities. Previous operation at knee joint.