9 studies (599 patients) were included in this meta-analysis comparing opening wedge high tibial osteotomy (OWHTO) to closing wedge high tibial osteotomy (CWHTO) for the treatment of unicompartmental knee osteoarthritis. Outcomes of interest included Visual Analog Scale (VAS) pain score, Hospital for Special Surgery (HSS) knee score, walking distance, Hip-Knee-Ankle (HKA) angle on radiograph, tibial slope on radiograph, complication rate and survival rate. The results from this study demonstrated no significant differences in the pooled VAS pain score, HSS knee score, walking distance, HKA angle, complications or survival rates. Results of pooled analysis on tibial slope demonstrated significantly higher tibial slope among groups treated with OWHTO compared to CWHTO.