OBJECTIVE To shift the weight-bearing axis of the lower limb medially by opening a lateral-based metaphyseal osteotomy at the distal femur. METHODS Femoral-based valgus malalignment and symptomatic lateral unicompartimental osteoarthritis, lateral hyperpression syndrome, cartilage therapy of the lateral compartment, lateral meniscal replacement/transplantation, medial instability with valgus thrust, reconstruction of the medial collateral ligament, patellar instability and/or maltracking. METHODS Advanced cartilage damage (>grade 2) or subtotal meniscal loss of the medial compartment, age >65 years (relative), nicotine abuse, body mass index >30, flexion contracture >25°, corrections with a wedge base >10 mm in case of congenital deformities, inflammatory or septic arthritis, severe osteoporosis. METHODS Lateral approach to the distal femur; biplanar osteotomy (frontal + axial osteotomy), gradual opening of the osteotomy, osteotomy fixation with a locking plate. METHODS Free range of motion. Partial weight bearing with 20 kg for 2 weeks, followed by progressive weight bearing thereafter. RESULTS Mean improvement of knee scores from 20-30 points and mean 10-year survival rate of 80% in patients with lateral unicompartimental osteoarthritis. Mean complication rate of 9%.