Causes of Patellofemoral Pain Syndrome
1. Overuse
In many cases, patellofemoral pain syndrome is caused by vigorous physical activities that put repeated stress on the knee -such as jogging, squatting, and climbing stairs. It can also be caused by a sudden change in physical activity. This change can be in the frequency of activity-such as increasing the number of days you exercise each week. It can also be in the duration or intensity of activity-such as running longer distances.

Other factors that may contribute to patellofemoral pain include:

Use of improper sports training techniques or equipment
Changes in footwear or playing surface

2. Patellar Malalignment
Patellofemoral pain syndrome can also be caused by abnormal tracking of the kneecap in the trochlear groove. In this condition, the patella is pushed out to one side of the groove when the knee is bent. This abnormality may cause increased pressure between the back of the patella and the trochlea, irritating soft tissues.

Factors that contribute to poor tracking of the kneecap include:

Problems with the alignment of the legs between the hips and the ankles. Problems in alignment may result in a kneecap that shifts too far toward the outside or inside of the leg, or one that rides too high in the trochlear groove-a condition called patella alta.

Muscular imbalances or weaknesses, especially in the quadriceps muscles at the front of the thigh. When the knee bends and straightens, the quadriceps muscles and quadriceps tendon help to keep the kneecap within the trochlear groove. Weak or imbalanced quadriceps can cause poor tracking of the kneecap within the groove.