Background and Etiology

The knee is the largest joint in the body. It is built for weight bearing, stability and mobility. The knee complex is composed of four bones and three osseous bone-to-bone joints. These are the patellofemoral joint, tibiofemoral joint and the tibiofibular joint.

The tibiofemoral joint is a hinge joint, located between the largest bone in the body (the femur) and the largest bone in the lower leg (the tibia.) When these two bones are joined together they form a medial and lateral compartment. The second joint in the knee complex, called the patellofemoral joint, is located between the patellar (knee cap) and the femur. The patellar glides up and down a groove on the anterior distal aspect of the femur. There is also a joint between the small lateral bone of the lower leg (fibula) and the larger tibia.

There are different degrees of instability that occur in the knee, including subluxation, which occurs in the patellofemoral joint. In some cases the patellar does not glide correctly along the groove in the anterior distal aspect of the femur because it is pulled toward the outside of the joint. This condition is called patellar subluxation.


A subluxation, or unstable kneecap, where the patellar does not glide along the groove properly may not cause any symptoms, or it may cause severe symptoms. In more severe conditions, a subluxation can lead to a dislocation where the patellar comes completely out of the groove. Patellar subluxation most often affects adolescents, and at times young children. People with loose or lax ligaments are most susceptible to this type of instability.

  • An abnormally wide pelvis
  • General ligamentous laxity may predispose an individual to instability.
  • A shallow groove along the anterior distal aspect of the femur
  • Abnormality in gait
  • Weakness of the medial quadriceps and tightness of the lateral soft tissue structures of the knee.
  • General tenderness of the knee area
  • Discomfort with movement, especially with bending activities
  • Feeling that the leg is “dead” after repeated activity
  • A feeling that the knee will “go out” when bending or twisting the leg. This is called the Apprehension Sign.

Conservative treatment of patellar subluxation is the first line of action. This includes physical therapy to reduce inflammation and associated pain. In addition, a regiment of exercises to improve muscular strength and patellar stability should be initiated. In more severe cases of instability involving a ligament injury, surgical intervention may be necessary. Patients may require taping or bracing to stabilize the patellar.

Physical Therapists are professionals, educated and trained to administer interventions. As stated in The Guide to Physical Therapist Practice interventions are the skilled and purposeful use of physical therapy methods and techniques to produce changes consistent with the diagnosis, prognosis, and the goals of the patient or client. Common interventions in the treatment of Patellar Subluxation include:

  • Manual Therapeutic Technique (MTT): hands on care, including soft tissue massage, and joint mobilization by a physical therapist to modulate pain and reduce any soft tissue or tendon irritation.
  • Therapeutic Exercises (TE) including strengthening exercises to improve strength of the muscles and ligaments in the knee and increase stability.
  • Neuromuscular Reeducation (NMR) to restore stability, begin retraining the lower extremity, improve proximal joint stability and improve movement technique and mechanics (for example, jumping, bending or twisting) in daily use of the involved lower extremity.
  • Modalities that can include the use of ultrasound, electrical stimulation, ice, cold laser and others to decrease pain and inflammation at the knee and tendons.
  • Home program that includes strengthening, stretching and stabilization exercises as well as instructions to help the person perform daily tasks and advance to the next functional level.

Procedures that your physician may recommend and perform in addition to physical therapy.

  • Relocation and initial immobilization of the dislocated patellar
  • REST and ICE
  • The use of NSAIDS (Non Steroidal Anti-Inflammatory Drugs)
  • Steroidal Injections to reduce inflammation
  • Pain medication to reduce the discomfort and allow the patient to perform the recommended exercises
  • Physical Therapy
  • The use of bracing or taping to improve patellar stability
  • In severe cases surgery to correct underlying pathology and avoid instability and repeated dislocations. This may include cartilage repairs or procedures to tighten the patellar ligaments.


Most people recover full function following a course of conservative care of physical therapy to strengthen and stabilize the patellar. Those with more involved conditions, like a ligament tear will require surgery and intensive physical therapy afterward to restore full function.

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