Effects of the amount of valgus correction for medial compartment knee osteoarthritis on clinical outcome, knee kinetics and muscle co‐contraction after opening wedge high tibial osteotomy

The goal of opening wedge high tibial osteotomy (HTO) is to reduce excessive loading on the medial compartment of the knee by correcting varus deformity, thereby reducing pain and improving function. Although surgical outcome is reportedly poor in cases of under‐ or overcorrection, the recommended alignment varies. The aim of this study was to investigate the effect of the degree of frontal plane knee alignment following open wedge HTO surgery on muscle co‐contraction, joint moments, and self‐reported functional outcome. Sixteen patients with medial compartment osteoarthritis (OA), who were scheduled for an opening wedge osteotomy, were recruited for participation in the study. Data were collected using an optoeletric motion analysis system and varus and valgus angulations of the knee were measured, using standing, long cassette, radiographs of the lower extremities. Results showed that physical function improved significantly overall (p < 0.001). However, those subjects whose knee alignment was further away from the group’s postoperative mean tended to improve less in their Knee Outcome Survey‐Activities of Daily Living Scale (KOS‐ADLS) scores than those closer to the mean (p = 0.07). They also had higher medial and lateral co‐contractions and higher adduction moments one year after surgery (p ≤ 0.009 and p = 0.048, respectively) and were more likely to show a change towards increased medial muscle co‐contraction following surgery, when compared to presurgical values. This outcome may contribute to accelerated degeneration of the knee for this group of people.