Patellar Maltracking (Patellofemoral syndrome) can be due to the anatomy of the patient’s body or specific activities. It is essential to understand the anatomy to better understand the underlying cause. The knee is composed of bones, ligaments, muscles, and cartilage. The three significant bones are the thigh bone (femur), the shin bone (tibia), and the knee cap (patella). The kneecap lies in a small groove in the femur called the trochlear groove. It is held in place by the quadriceps tendon on top and the patella tendon on the bottom.
There are variations in anatomy that causes some patients to be more prone to dislocation. If the trochlea is too shallow, the patella is more likely to dislocate. If a person has anatomy with a wider placement of the hip bones, they may also experience instability. This is often the case in young individuals, particularly women. Lastly, people with connective tissue disorders, such as Ehlers Danlos or Marfan’s Syndrome, have lax ligaments that allow instability.
Certain activities can also cause patellar maltracking. Damaging the stabilizing ligaments on the medial side of the patella, called the medial patellofemoral ligament (MPFL) is associated with 70-100% of cases of lateral patellar dislocation. Additionally, injuries that cause cartilage damage and inflammation can cause bony growth that creates an irregular surface between the patella and the trochlea. Activities that cause such injuries include trauma caused by motor vehicle collisions, sports that require quick changes in direction, such as soccer or basketball, and running.