Background and Aim: Anterior knee pain (AKP or AnKP) is one of the most common disorders of knee. Many studies have been implemented about anterior knee pain and effect of different treatments on this disorder. Todays, this general term has been divided and studied more closely. Knee extension syndrome is one of the common disorders in orthopedic and physical therapy that diagnosed with increased stiffness of quadriceps muscle and causes anterior knee pain. The purpose of this review article is to evaluate this disorder more closely.

Materials and Methods: A literature search was carried out using MEDLINE and SCIENCE DIRECT cite and JOSPT journal database to assess existing literature about anterior knee pain. Furthermore, literatures about the different standpoints of anterior knee pain and effectiveness of different treatments and interventions of anterior knee pain and knee extension syndrome have been identified.

 Results: Fifty articles have been surveyed: forty-two articles evaluated the effect of different treatments on anterior knee pain. Five articles evaluated the various aspects of anterior knee pain more closely and three ones related to knee extension syndrome.

Conclusion: According to these studies results, the causes of anterior knee pain can be classified in two categories: 1) anterior knee pain associated with patellofemoral disorders and 2) anterior knee pain non-associated with patellofemoral disorders. The knee extension syndrome is the cause for anterior knee pain but non-associated with patellofemoral disorders. In this disorder, the tilt angle of patella could be increased and this factor can increase the patients' pain. In contrast to general belief that focuses on tensor fascia lata- ilotiobial band complex (TFL-ITB complex), the rectus femoris muscle stretching should be focused more, because the ilotiobial band has a less effect on patellar tilt.