Accessibility Tools
Anthony J. Berni, MD Orthopedic Surgeon

Anthony J. Berni, MD Orthopedic Surgeon

View Profile

Patellofemoral Instability (Knee)

Patellofemoral Instability results from one or more dislocations or partial dislocations, also called subluxations. This misalignment can damage the underlying soft structures such as muscles and ligaments that hold the knee in place. Once damaged, these soft structures are unable to keep the patella (knee cap) in position.

Signs and symptoms of Patellofemoral Instability can include the following:

  • Pain, especially when standing up from a sitting position
  • Feeling of unsteadiness or tendency of the knee to “give way” or “buckle”
  • Recurrent Subluxation: When the kneecap slips partially out of place repeatedly
  • Recurrent Dislocation: When the kneecap slips all the way out of position repeatedly
  • Severe pain, swelling and bruising of the knee immediately following subluxation or dislocation
  • Visible deformity and loss of function of the knee often occurs after subluxation or dislocation
  • Sensation changes such as numbness or even partial paralysis can occur below the dislocation as a result of pressure on nerves and blood vessels


Patellofemoral Instability can be caused by a number of factors that affect the way the patella moves along the groove of the femur (trochlear groove) when the leg is bent or straightened. The patella normally moves up and down with a slight tilt without touching the other knee bones. In Patellofemoral Instability, the patella does not maintain its normal path of movement and can slip out of the trochlear groove either partially (subluxation) or completely (dislocation).


Evaluating the source of Patellofemoral Instability is critical in determining your treatment options for relief of the instability. Your physician will perform the following:

  • Medical History
  • Physical Examination
  • Diagnostic studies such as X-rays, CT scan, or MRI

The goal of conservative treatment for Patellofemoral Instability is to restore full range of motion by restoring the normal tracking pathway of the patella during flexion and extension of the knee. Treatment options may include closed reduction, pain medications, rest, ice, physical therapy, orthotics, and bracing. Surgical treatment of Patellofemoral Instability is sometimes necessary to help return the patella to a normal tracking path when conservative treatment options are unsuccessful.


  • J Berni MD Orthopedic Surgeon American Acaadmey Of Orthopaedic Surgeon
  • American board Of Orthopaedic Surgery
  • J Berni MD Orthopedic Surgeon Saint Louis University
  • J Berni MD Orthopedic Surgeon University Of Missouri-Health
  • J Berni MD Orthopedic Surgeon St Charles Orthopadeic Surgery Associate