To compare lateral closing to medial opening wedge high tibial osteotomy regarding change in proximal tibial anatomy and PCL tibial attachment integrity after standard tibial arthroplasty resection. Controlled cadaveric study. Ten cadaveric lower limbs received either a 12 degrees lateral closing or 12.5-mm medial opening wedge high tibial osteotomy. Radiographs were performed before and after each osteotomy, and each PCL tibial attachment was dissected. Postosteotomy, tibial arthroplasty resection was performed and the remaining PCL attachment area calculated. Lateral closing wedge specimens demonstrated a greater change in proximal tibial anatomy. After tibial arthroplasty resection, there was a significant difference in remaining PCL tibial attachment percentage area. Proximal tibial anatomy is altered differently for each type of osteotomy despite similar correction angles. Arthroplasty conversion may be more challenging after lateral closing wedge procedures.