The study will investigate an association between ankle dorsiflexion and altered frontal knee kinematics during step down test in patients with PFPS.

Altered frontal and transverse plane hip kinematics during single leg weight-bearing tasks are thought to be important contributors to patellofemoral pain (PFP). The closed chain nature of single leg tasks means that hip kinematics can be influenced by more distal mechanics, such as foot pronation.

One of the often-studied distal movements theorized to cause PFPS is pronation of the subtalar joint. Pronation is a tri-planar movement that includes dorsiflexion, eversion, and abduction of the foot. Many studies have examined eversion characteristics of PFPS patients, but the dorsiflexion aspect of the movement has been shown to be a possible risk factor, restricting dorsiflexion was shown to increase medial knee displacement in young healthy adults. Conversely, when available dorsiflexion ROM is increased, medial knee displacement is thought to decrease.

Patients with PFPS were observed to have a decreased DFROM (dorsiflexion range of motion) as compared to normal individuals, though this topic has not thoroughly been investigated.

Inclusion Criteria:

1. Anterior or retropatellar knee pain from at least 2 of the following Activities : (1) prolonged sitting; (2) stair climbing; (3) squatting; (4) running; (5) kneeling; and (6) hopping/jumping.
2. Insidious onset of symptoms unrelated to a traumatic incident and persistent for at least 6weeks.
3. VAS equal to or greater than 3.
4. Age of the subject 18-35 years to limit the possibility that PFPS over age 35 may have been complicated by arthritic changes, and also the subjects should have closed epiphyseal growth plates.
5. BMI under 30 kg/m2, both gender

For the control group, subjects were recruited to this study if they had:

1. No previous history or diagnosis of knee pathology.
2. No pain with any of the above-mentioned provocative activities.
3. No history of lower limb or spinal pathology.

Exclusion Criteria:

1. A history of any of the following condition: meniscal or other intraarticular pathologic conditions; cruciate or collateral ligament involvement.
2. A history of traumatic patellar subluxation or dislocation.
3. Previous surgery in the lower extremities within the 12 months prior to participation in the study.
4. Any balance impairments are secondary to a vestibular or neurological disorder or secondary to the use of medication.
5. Any lower limb bony/congenital deformity

Subjects between 18 to 35 years old with symptomatic patellofemoral pain syndrome and healthy control.