Purpose: When performing total knee arthroplasty (TKA) in valgus knee deformities, a medial or lateral parapatellar approach can be performed, but the lateral approach is often considered technically more difficult. The purpose of this study was to compare intra-operative, early clinical and radiological outcomes of medial and lateral parapatellar approaches for TKA in the setting of moderate knee valgus (<10°). Methods We prospectively analysed 424 knees with preoperative valgus deformity between 3° and 10° that underwent TKA over an 18-year period; 109 were treated with a medial approach and 315 with a lateral approach. Intra- and post-operative outcomes and complication rates after a minimum follow-up of one year were compared.

Results: Tourniquet (p=0.25) and surgical (p=0.62) time were similar between groups. The popliteus tendon was released more frequently in the medial-approach group (p=0.04), while the iliotibial band was released more frequently in the lateral-approach group (p<0.001). A tibial tuberosity osteotomy was performed more frequently in the lateral- than medial-approach group (p=0.003). No significant differences in limb alignment (p=0.78), or Knee Society Score (KSS) knee (p=0.32) and function (p=0.47) results were noted based on surgical approach, and complication rates were similar between groups (p=0.53).

Conclusions: Lateral parapatellar approach is a safe and effective surgical technique for performing TKA in moderately valgus knees. These equivalent early results are encouraging for systematic use of the lateral approach in moderately valgus knees.