Patellar tracking disorder (PTD) is a painful condition caused by a problem with the bones, muscles or ligaments around the kneecap (or patella). The patella is held in place by the tendons and ligaments around it. A layer of cartilage is present behind the kneecap to prevent friction. PTD occurs when the kneecap shifts out of place when the leg bends or straightens. In most cases, the kneecap shifts too far toward the outside of the leg, although in a few people it shifts toward the inside. Misalignment, muscle imbalance or ligament damage causes the patella (kneecap) to shift from its proper location, resulting in PTD. It commonly occurs in individuals who are involved in sports that require repeated jumping, knee bending or squatting. PTD occurs more frequently in adolescents than adults, and it is more frequent in females than males.

Generally, PTD is treated by measures such as avoiding the activities causing pain, putting ice on the knee, and using exercises to strengthen the muscles of the leg and hip. There are generally no complications associated with PTD. Most cases show a 95% improvement with a prescribed exercise schedule.

Causes of Patellar Tracking Disorder

PTD is caused by combination of several factors, as described below:

  • Misalignment between the joint surfaces (since the knee joint is composed of two leg bones and one thigh bone)
  • Weakness of the thigh muscles
  • Tendons, ligaments or muscles in the leg that are too tight or too loose
  • Activities that stress the knee again and again, especially those with twisting motions
  • A traumatic injury to the knee, such as a blow that pushes the kneecap toward the outer side of the leg
  • Problems with the structure of the knee bones or how they are aligned

Symptoms of Patellar Tracking Disorder

The signs and symptoms associated with PTD include:

  • Knee pain
  • Pain that is aggravated by activities such as squatting, jumping, kneeling and using the stairs
  • A feeling of popping and grinding in the knee, when it is bent or straightened
  • The knee seems to buckle under one’s own weight
  • One or both knees can be involved
  • Increased mass of one of the thigh muscles, called Vastus medialis