Knee pain improvement following total hip arthroplasty : a prospective study on frequency, severity, and influencing factors.

Abstract

Patients with hip pathology frequently report concurrent knee pain before total hip arthroplasty (THA). This prospective study aimed to evaluate the frequency and severity of knee pain before and after THA, and analyze the factors influencing knee pain. Data were collected from 149 primary THAs for hip osteoarthritis (OA) in 147 patients. Knee and hip pain were assessed using a visual analogue scale (VAS) preoperatively, and three, six, and 12 months postoperatively. We analyzed: 1) changes in knee pain severity before and after THA; 2) prevalence of knee pain before and after THA; and 3) factors affecting the severity of knee pain before and after THA. The knee VAS scores significantly decreased from 2.2 before THA to 1.1 at three months, 0.8 at six months, and 0.7 at 12 months after surgery. The prevalence of knee pain also significantly decreased from 52.3% (n = 78) before THA to 37.6% (n = 56) at three months, 29.5% (n = 44) at six months, and 27.5% (n = 41) at 12 months after surgery. The preoperative hip VAS score positively influenced, and the preoperative pelvic tilt negatively influenced, the preoperative knee VAS score. In contrast, Kellgren-Lawrence grade in the knee and postoperative varus whole-leg alignment, in addition to the preoperative knee VAS score, positively influenced the knee VAS score 12 months after surgery. Approximately half of the patients experienced knee pain before THA, influenced by the severity of their preoperative hip pain. Notably, both the severity and prevalence of knee pain showed significant improvement following THA. Patients with radiological knee OA, postoperative varus alignment, and severe preoperative knee pain were more likely to experience persistent knee pain at 12 months after THA.