A new technique in oblique incomplete high tibial osteotomy that permits an increase of valgus correction while preventing fracture of the medial cortex was investigated. Closing wedge or opening wedge osteotomy was done on 23 tibias from cadavers before loading in an Instron testing machine. In seven specimens (Group 1), lateral oblique wedge osteotomy was done. In seven other specimens (Group 2), one medial oblique cut was made. In both groups, the osteotomy terminated 10 mm from the cortex and approximately 2 cm below the plateau. In nine specimens (Group 3), the osteotomy terminated in a 5-mm diameter hole, drilled in an anteroposterior direction, with its center positioned 10 mm from the medial cortex and 2 cm below the articular surface. The maximum angle of opening or closing before fracture of the cortex took place was recorded. In Groups 1 and 2, similar maximum correction angles were observed, 6.7 degrees versus 6.5 degrees, respectively. In Group 3, the stress relieving hole allowed the correction angle to be increased to 10 degrees. An oblique high tibial valgus closing wedge osteotomy with an apical drill hole allows a significant increase of the correction angle compared with the same osteotomy without a drill hole. Medial open wedge osteotomy offers no advantage over lateral closed wedge osteotomy in the maximum obtainable correction angle without failure of the cortex.