Effect of anatomic realignment on muscle function during gait in patients with medial compartment knee osteoarthritis.

OBJECTIVE

Individuals with medial compartment knee osteoarthritis (OA) and genu varum use different movement and muscle activation patterns to increase joint stability during gait. The purpose of this study was to ascertain whether opening-wedge high-tibial osteotomy (OW-HTO) corrected pathomechanical abnormalities associated with the progression of knee OA.

METHODS

Fifteen patients diagnosed with medial knee OA and genu varum who were scheduled for OW-HTO were tested prior to and 1 year following OW-HTO. Fifteen age- and sex-matched controls were also tested. Frontal plane laxity was measured from stress radiographs. All participants underwent quadriceps strength testing with a burst superimposition technique and gait analysis with surface electromyography to calculate knee joint kinematics and kinetics and muscle co-contraction during the stance phase of gait. Participants rated their knee function and instability using a self-report questionnaire.

RESULTS

Static alignment improved following the surgery. Medial laxity (P = 0.003) and instability (P = 0.002) significantly improved, and statistical reductions in the adduction moment resulted in lower levels of vastus medialis-medial gastrocnemius muscle co-contractions (P = 0.089). Despite improvements in global rating of knee function (P = 0.001), the OA group's ratings remained significantly lower than those of the healthy controls (P = 0.001). Quadriceps strength deficits and knee flexion impairments persisted.

CONCLUSIONS

Persistent quadriceps weakness and impaired knee kinematics after realignment suggest that the movement strategy may perpetuate joint destruction and impede the long-term success of realignment. Rehabilitation should focus on quadriceps strength and improving joint mobility to improve the long-term function of individuals with medial knee OA.