Patellofemoral Instability

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Patellofemoral instability is a result of the patella (kneecap) moving out of its normal pattern of alignment. This malalignment can damage the muscles and ligaments that hold the knee in place. There are a number of scenarios that cause patellofemoral instability including arthritis and sports-related conditions.

At OrthoAspen we are dedicated to helping our active patients resume the activities to which they are accustomed—as quickly and safely as possible.

Causes & Symptoms

Patellofemoral instability can be caused as a result of variations in the shape of the patella or its trochlear groove as the knee bends and straightens. Normally, the patella moves up and down within the trochlear groove when the knee is bent or straightened. Patellofemoral instability occurs when the patella moves either partially (subluxation) or completely (dislocation) out of the trochlear groove. Young active individuals involved in sports activities are more prone to patellofemoral instability.

Additional causes and factors that lead to patellofemoral instability include:

  • Anatomical Defects
    Flat feet or fallen arches and congenital abnormalities in the shape of the patella bone can cause misalignment of the knee joint.
  • Abnormal “Q” Angle
    A high “Q” angle (angle between the hips and knees) often results in abnormal tracking of the patella evidenced, for example, in patients with knock knees (a condition when the knees touch, but the feet/ankles don’t).
  • Patellofemoral Arthritis
    Patellofemoral arthritis occurs when there is a loss of the articular cartilage on the back of the kneecap. This can eventually lead to abnormal tracking of the patella.
  • Improper Muscle Balance
    Weak quadriceps (anterior thigh muscles) can lead to abnormal tracking of the patella, causing it subluxate or dislocate.

Symptoms of patellofemoral instability include:

  • Pain when standing up from a sitting position
  • Sensation of the knee buckling or giving way
  • Severe pain, swelling and/or bruising when the kneecap slips either partially or completely
  • Deformity of the knee and/or loss of function
  • Numbness or even partial paralysis below the dislocation because of pressure on nerves and blood vessels

To effectively diagnose patellofemoral instability your OrthoAspen doctor will go over your medical history and perform a physical examination. Other diagnostic tests such as X-rays, MRIs and CT scans may be done to determine the cause of your knee pain and to rule out other conditions.


Whenever possible, our OrthoAspen sports medicine specialists will apply conservative treatment methods.

If your kneecap is only partially dislocated (subluxation), your physician may recommend nonsurgical treatments such as:

  • Pain medications
  • Rest
  • Ice
  • Physical therapy
  • Knee-bracing and orthotics

If the kneecap has been completely dislocated, it may need to be repositioned back in its proper place in the groove. This process is called closed reduction.

This treatment is only necessary once nonsurgical treatments have failed.

Patellar realignment surgery is broadly classified into proximal realignment procedures and distal realignment procedures.

  • Proximal Realignment Procedures
    During this procedure, structures that limit the movements on the outside of the patella are lengthened or ligaments on the inside of the patella are shortened.
  • Distal Realignment Procedures
    During this procedure, the Q angle is decreased by moving the tibial tubercle toward the inner side of the knee.

Surgery begins with your OrthoAspen surgeon applying two or three small cuts around the knee. An arthroscope, a narrow tube with a tiny camera on the end, is inserted through one of the incisions to view the knee joint. Specialized instruments are inserted into the joint through other small incisions.

The camera attached to the arthroscope displays the image of the joint on the monitor. A sterile solution is pumped into the knee to stretch the area and provide a clear view, in addition to providing room for the surgeon to work. With the images from the arthroscope as a guide, your surgeon can look for any pathology or anomaly and repair it through the other incisions with various instruments.

After the evaluation is completed, a larger incision is made over the front of the knee. Depending on the specific situation, a lateral retinacular release may be performed. In this procedure, the tight ligaments on the outer side of the knee are released. This allows the patella to sit properly in the femoral groove. Your surgeon may also tighten the tendons on the inside or medial side of the knee to realign the quadriceps.

In cases where the malalignment is severe, a procedure called a tibial tubercle transfer (TTT) will be performed. In this procedure, a section of bone where the patellar tendon attaches to the tibia is removed. This bony section is then shifted and properly realigned with the patella and reattached to the tibia using screws. Once the malalignment is repaired and confirmed with arthroscopic evaluation, the incisions are closed with sutures.


What should I expect after surgery in terms of pain, swelling and returning to activities?

Your OrthoAaspen surgeon will recommend:

  • Medications to relieve pain
  • Elevation of the leg to help reduce swelling
  • Application of ice packs over the knee
  • Crutches are necessary for the first few weeks to prevent weight bearing on the knee
  • Knee immobilizer to stabilize the knee
  • Avoidance of activities that exacerbate symptoms
  • A rehabilitation program for a faster recovery

Are there any common risks?

Possible risks and complications associated with the surgery include:

  • Knee extension difficulty or complete inability to extend the leg and knee
  • Recurrent dislocations or subluxations
  • Arthrofibrosis (thick fibrous material around the joint)
  • Pain that is persistent

At OrthoAspen, we are dedicated to helping you recover as safely and quickly as possible.

If you’re concerned that you may be experiencing patellofemoral instability, contact us today to schedule a consultation, or call us at 970-544-1289.


Visit OrthoAspen in two convenient locations
Aspen Clinic
Aspen Valley Hospital
0401 Castle Creek Rd., Suite 2100,

Aspen, CO 81611
+(970) 544-1289
+(970) 544-1400
Basalt Clinic
Midvalley Medical Center
1450 E. Valley Rd., Suite 201,

Basalt, CO 81621
+(970) 544-1289
+(970) 544-1400