An Overview of Patellar Instability

The knee is a complex joint composed of numerous important structures including bones, ligaments, tendons and menisci. The patella (kneecap) is one of these important structures. When the kneecap becomes displaced from its intended resting place, it is defined as patellar instability. Instability can occur from a dislocation, from poor movement patterns during athletic activities or from muscle weakness and other physical abnormalities. No matter the cause of patellar instability, the knee specialists at Texas Sports Medicine are available to diagnose and treat the condition in Dallas, Frisco and Fort Worth, Texas area patients.

What is Patellar Instability?

In a healthy knee, the patella (kneecap) rests in the trochlea (groove) at the end of the femur (thigh bone). When the knee straightens and bends during everyday, work and athletic activities, the patella should stay in the groove and slide up and down.

Patellar instability occurs when the kneecap comes out of the groove while the knee is bending and/or straightening. In certain individuals, the kneecap may not stay in its intended location even while at rest.

Instability of the kneecap can be the result of a specific traumatic event, develop over time with no specific cause or be the result of a physical abnormality.

Two of the most common traumatic events that cause patellar instability include a direct hit to the knee joint and changing directions too quickly while running (cutting) during athletic activities. Both of these events can cause the kneecap to be forcefully pushed out of the groove, known as a patellar dislocation. A dislocation often requires the kneecap to be placed back in the proper position. After the dislocation occurs, the surrounding supporting structures are often stretched and too loose to hold the kneecap in the groove properly, leading to chronic instability.

Females are more prone than males to experience patellar instability without a specific injury. Subluxation occurs when the kneecap comes partially (sublux) out of the groove with normal daily activities. Even though the patella is not completely out of its groove like a dislocation, a subluxation will still cause pain and instability that worsens over time.

Patellar instability also has the possibility to be caused by a number of anatomical abnormalities. Common abnormalities include a shallow or rotated groove (trochlea), muscle weakness in the hip and knee regions, ligament and tendon malfunction and poor movement patterns while running, jumping, landing and engaging in athletic activities.

Symptoms of Patellar Instability

  • Knee pain worsened when using stairs, squatting, jumping, landing or running
  • A sensation the kneecap is shifting or sliding
  • Leg and knee weakness
  • Swelling and stiffness

Treatment of Patellar Instability


  • Ice
    • Apply ice packs to the affected knee several times a day
  • Bracing
    • Hold the kneecap in its proper position
  • Rest
    • Stop all activities that worsen symptoms
  • Physical therapy
    • Range of motion and strengthening exercises to help control movement and stability


  • Surgery
    • Surgical technique: Depending on the cause of instability, a damaged ligament may be reconstructed, tight soft tissues may be released or bone alignment changes may be performed on the shin bone.

After Surgery

Recovery options vary depending on the operative treatment performed to correct the case of patellar instability. All patients will be prescribed detailed rehabilitation instructions that must be followed for a successful treatment outcome.

For more information on patellar instability, please contact the knee specialists at Texas Sports Medicine serving the communities of Dallas, Frisco and Fort Worth, Texas.