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Patellar Instability

What is patellar instability?

Patellar instability, also known as kneecap instability, is a condition characterized by the abnormal movement or dislocation of the patella (kneecap) from its normal position within the femoral groove. This instability can lead to pain, swelling, and difficulty with knee function, particularly during activities that involve bending or straightening the knee.

What are the causes of patellar instability?

Several factors may contribute to the development of patellar instability:

  • Trauma: Direct impact or force to the knee, such as falls or sports-related injuries.
  • Anatomical Factors: Structural abnormalities in the knee joint, such as shallow or tilted femoral groove, excessive Q-angle, or abnormal patellar shape.
  • Muscle Weakness or Imbalance: Weakness or imbalance in the muscles surrounding the knee, particularly the quadriceps and hip abductor muscles.
  • Ligamentous laxity: Increased looseness or laxity in the ligaments supporting the knee joint, predisposing to patellar instability.

What are the symptoms of patellar instability?

Symptoms of patellar instability may include:

  • Patellar Dislocation: Complete or partial displacement of the patella from its normal position, often accompanied by a visible deformity.
  • Swelling: Swelling and inflammation around the knee joint, especially following episodes of dislocation.
  • Pain: Sharp or aching pain in the front of the knee, particularly with movement or weight-bearing activities.
  • Instability: Feeling of the knee “giving way” or buckling, especially during physical activity or when changing directions.

How is patellar instability diagnosed?

Diagnosis of patellar instability typically involves a thorough physical examination and may include imaging studies such as X-rays, MRI, or CT scans to assess the extent of damage and underlying anatomical factors contributing to instability.

At a Glance

Dr. Shane Nho

  • Board-certified, fellowship-trained orthopedic surgeon
  • Team Physician for Chicago Bulls, White Sox, Steel
  • Performs more than 700 procedures each year
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