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Patellar Dislocation

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 patellarfemoral 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 larges 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 patellarfemoral 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.

The ligaments, cartilage, and mensici provide stability to the knee joint. There are different degrees of instability that occur in the knee, like dislocation. When referring to knee dislocation, we are referring primarily to the patellarfemoral joint.

Dislocation

A patellar dislocation occurs when the patellar actually comes out of the groove along the anterior distal aspect of the femur, where it slides up and down to facilitate movement of the joint. Dislocations are most common in the younger population. Ligament tears, or cartilage and meniscus injuries may be secondary to a patellar dislocation. Repeated dislocations can result in permanent ligament laxity, which causes chronic reoccurring dislocations.

Causes

  • Patellar subluxation, where the patellar is pulled to the side of the groove in the patellarfemoral joint is the most common cause of patellar dislocation.
  • General ligamentous laxity may predispose an individual to dislocation.
  • Repetitive strain injuries (RSI) at work, or overuse activities are common in people who participate in sport activities and individuals who have jobs that require performing activities of a repetitive nature.
  • Sudden trauma or accident like a fall on the knee.

Symptoms

  • Significant pain in the knee
  • Individuals will prefer to keep the leg held at the side, and may feel an inability or unwillingness to move the leg.
  • Loss of normal rounded contour of the knee
  • Swelling, weakness, numbness and occasional bruising of the knee area

Treatment

Physicians reduce acute dislocations using several techniques, which may or may not require radiographic examination.

  • Age and activity level are factors that guide treatment
  • In young athletes (15 to 25 years old) surgical intervention is considered based on the high risk of recurrence, apprehension, impact on sports participation and quality of life
  • Generally arthroscopic repair is used for the younger population
  • There is a lower rate of occurrence among 25 to 40 year olds therefore members of this population respond better to conservative interventions
  • People 40 years old and over have an even lower rate of recurrence, but do have increased risk of residual disability from nerve or vascular injuries
  • Conservative treatment whether post surgical or non-surgical is typically recommended
  • Typically a period of immobilization with the leg held in internal rotation for up to six weeks is recommended

Physical Therapy Interventions

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 Dislocation 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 while helping to restore motion following a period of immobilization. Movements should avoid positions that place the knee in the position that produced the dislocation (Apprehension Sign).
  • Therapeutic Exercises (TE) including exercises to strengthen the muscles in the knee and increase patellar stability. Emphasis should be placed on the internal rotators and anterior muscles of the knee.
  • Neuromuscular Reeducation (NMR) to restore stability, begin retraining the lower extremity, improve proximal joint stability and improve movement technique and mechanics (for example, jumping) in daily use of the involved lower extremity.
  • Modalities including 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.

Medical Interventions

  • Procedures that your physician may recommend and perform in addition to physical therapy.
  • Relocation and initial immobilization of the dislocated knee
  • 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
  • Surgery to correct underlying pathology and avoid instability and repeated dislocations. This may include procedures to tighten the ligaments.

Prognosis

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