The objective of this study was to analyze two surgical techniques in the treatment of fibrous rectus femoris muscle in children. Data from 152 patients (161 knees) from July 1991 to December 2004 were analyzed. Clinical signs were knee stiffness in swing phase, positive Ely and Ober tests, and abnormal flexion angles of the knee and hip. Patients were operated according to one of two variants: variant A, to release the proximal tendon and variant B, to release the middle shaft of the rectus femoris muscle. There were 96 women (63.2%) and 56 men (36.8%) in this study. Bilateral involvement was found in nine patients; only the left knee was affected in 34 patients (22.4%) and only the right knee in 109 patients (71.7%). All 152 patients (161 knees) developed fibrous rectus femoris muscle (RFM) after repeated intramuscular injection of antibiotic(s) into the RFM. A total of 145 knees (136 patients) were classified as severe and 16 knees (16 patients) were classified as moderate. Overall, we attained excellent results in 109 (67.7%), good results in 26 (16.1%), fair results in 14 (8.7%), and poor results in 12 knees (7.5%). There have been no complications so far. Generally, surgical treatment of knee stiffness in swing phase due to fibrous RFM according to variant B led to postoperative poor results in only 1.2% of patients, whereas variant A gave postoperative poor results in 14.5% of patients. The surgical procedure is simple and safe, and knee and hip functions, tendency for crouch gait, and anterior pelvic tilt were remarkably improved.