BACKGROUND:Lateral retinacular release is effective to treat anterior knee pain, but it has not been confirmed through the parameters of the knee joint. OBJECTIVE: To analyze the relevant parameters on the axial X-ray films of the patela before and after lateral retinacular release and then to find out the efficient parameters for patelofemoral joint disorders on the axial X-ray film of the patela, which are of most clinical significance. METHODS: Fifty patients with anterior knee pain were included randomly who admitted at the Department of Joint Surgery, Affiliated Hospital of Jining Medical University from February 2009 to December 2013, including 45 cases of Outerbridge I-III undergoing arthroscopic lateral retinacular release+articular cartilage repair and 5 cases of Outerbridge IV undergoing lateral retinacular release+knee joint surface replacement. RESULTS AND CONCLUSION:After lateral retinacular release, the congruence angle, patelofemoral index and tilt angle were al reduced significantly (P < 0.05 orP < 0.01), but there was no change in the lateral patelofemoral angle (P > 0.05). The patelar trajectory restored to the corresponding central position of the femoral condyle, and meanwhile, no joint hematoma, deep vein thrombosis and patelar subluxation occurred. These findings indicate that the lateral retinacular release is of great significance for treatment of anterior knee pain induced by lateral patelofemoral compression.