Introduction: Angular deformities of the tibia and femur lead to mechanical axis deviation (MAD) of the lower limb and malorientation of the joints adjacent to the deformity. The current study analyses the outcomes of using a medial closing wedge high tibial osteotomy (MCWHTO) for the management of genu valgum with high medial proximal tibial angle (MPTA), and combined MCWHTO with lateral opening-wedge distal femoral osteotomy (LOWDFO) in the setting of concomitant genu varum with low lateral distal femoral angle (LDFA). Methods: There were 18 high tibial osteotomy (HTO)-only and 13 combined HTO + distal femoral osteotomy (DFO) procedures performed. The primary radiographic outcome variables included postoperative MPTA and MAD (in mm). The accuracy of MAD correction was expressed as a percentage. The postoperative posterior proximal tibial angle (PPTA) and limb length discrepancy (LLD) were also measured as secondary radiographic outcome variables. The clinical outcome variables included intraoperative surgical complications (e.g., hinge fracture), all-causes for revision, union rate, time to union, and postoperative knee range of motion. Functional outcomes used included the LDSRS, PROMIS, and EuroQOL scores. Results: The mean preoperative MPTA was 92.9° (SD = 1.81, range: 88–96). After surgical correction, the mean MPTA was 86.0° (SD = 1.80, range: 83–90) (p < 0.0001). The mean preoperative MAD was 32.5 mm (SD = 20.16, range: 10–77) lateral to the centre of the knee joint. The mean postoperative MAD was 2.44 mm medial to the centre of the joint (SD = 7.13, range: 13 medial – 15 lateral) (p < 0.0001). The mean change in MAD achieved through surgical correction was 38.16 mm (SD = 17.94, range: 13–77). The accuracy of MAD correction was 96.1% (SD = 0.06%, range: 81.25–100%). The time to unassisted WB was a mean of 75 days (SD = 44.5, range: 44–242). There was a single stable hinge fracture and one case of chronic regional pain syndrome diagnosed. There were no cases of non-union and no indications for revision surgery in any case. Conclusion: Medial closing wedge high tibial osteotomy is an effective surgical procedure for the management of genu valgum deformity. The MPTA, LDFA, and MAD can be accurately corrected without significantly altering PPTA or limb length. It may be combined with open lateral distal femoral osteotomy for cases with femoral and tibial contributions to deformity without significantly impacting clinical outcomes. Functional outcomes, specifically relating to self-image are significantly improved after the MCWHTO has been performed.