The Clinical Consequences of Flexion Gap Asymmetry in Total Knee Arthroplasty

This study was carried out to compare femoral component rotation of 18 knees from 18 patients who suffered from lateral flexion instability after total knee arthroplasty (Western Ontario and McMaster University Osteoarthritis [WOMAC], 6.4 points; International Knee Society [IKS] score, 119 points) with 10 asymptomatic controls (WOMAC, 0.1 points; IKS score, 182 points) after total knee arthroplasty. The symptomatic patients showed increased lateral joint laxity as determined by fluoroscopic stress radiography. Femoral component rotation was determined by computed tomography scans. The femoral component rotation was more internally rotated in symptomatic patients (5.5°) than in controls (1.0°) (P = .04). Varus laxity in flexion was higher in symptomatic patients (11.0°) than in controls (7.0°) (P < .001). Increased lateral flexion laxity is associated with increased internal femoral component rotation and a less favorable clinical outcome.