Abstract: Objective To investigate the effect of minimally invasive hip arthroplasty on joint function and synovial fluid laboratory indexes in patients with knee osteoarthritis. Methods Ninety patients with knee osteoarthritis were divided into the control （n = 45） and observation groups （n = 45） according to the treatment method. In the control group, patients received traditional hip arthroplasty, and those in the observation group underwent minimally invasive hip arthroplasty. The perioperative indexes including incision length, operation time, intraoperative bleeding volume, postoperative drainage volume, ambulation time and length of hospital stay were statistically compared between two groups. The knee joint function was assessed by the American Special Surgical Hospital Knee Function Scale （HSS） before and 3 months after surgery. The levels of C-reactive protein （CRP）, erythrocyte sedimentation rate （ESR） and procalcitonin （PCT） in the synovial fluid were measured and the incidence of complications was recorded. Results The incision length, intraoperative bleeding volume and length of hospital stay in the observation group were significantly less than those in the control group （all P < 0.05）. Postoperatively, the HSS scores were remarkably higher than those before treatment in two groups （both P < 0.05）, whereas the levels of CRP, ESR and PCT in the synovial fluid were significantly lower than those before treatment （all P < 0.05）. The scores of muscle strength, joint activity, joint stability, function and flexion deformity in the observation group were significantly higher compared with those in the control group （all P < 0.05）, whereas the levels of CRP and PCT in the synovial fluid were considerably lower than those in control group （both P < 0.05）. The incidence rate of incision infection, deep venous thrombosis, dislocation and prosthesis loosening did not significantly differ between two groups （all P > 0.05）. Conclusions Compared with traditional hip arthroplasty, minimally invasive hip arthroplasty can shorten the incision length and length of hospital stay, reduce intraoperative blood loss, promote postoperative recovery of joint function, and mitigate inflammatory reaction.