The inclination of the joint line after supracondylar osteotomy of the femur for valgus deformity was studied in 22 patients and 26 knees. The patients (4 males and 18 females) were 17 to 77 years old (mean, 49.5 years). The obliquity of the joint line was measured in positive degrees (medial inclination) and negative degrees (lateral inclination). Mean obliquity was +3.1 degrees in the preoperative study and -2.0 degrees in the post-operative study. Significant horizontality of the joint line was obtained when the two periods were compared (mean, 5.0 degrees).