Patellar Maltracking and Instability

What is Patellar Maltracking and Instability?

Patellar (kneecap) instability results in one or more dislocations or partial dislocations (subluxations) of the patella over the (usually) outer side of the femoral groove it sits within. The patella is the small piece of bone in front of the knee that slides up and down the femoral groove (groove in the femur bone) during bending and straightening movements. The ligaments on the inner and outer sides of patella hold it in the femoral groove and avoid dislocation of patella from the groove. Any damage to these ligaments may cause patella to slip out of the groove either partially (subluxation) or completely (dislocation). This misalignment can further damage the underlying soft structures such as muscles and ligaments that hold the kneecap in place. Once damaged, these soft structures are less able to keep the patella (kneecap) in it’s correct position.

Symptoms of Patellar Maltracking and Instability

Patients with knee instability experience different signs and symptoms such as:

Pain, especially when standing up from a sitting position
Feeling of unsteadiness or tendency of the knee to “give way” or “buckle”
Recurrent subluxation/ dislocation
Visible deformity and loss of function of the knee often occurs after subluxation or dislocation

Causes of Patellar Maltracking and Instability

Various factors and conditions may predispose to patellar instability. Often a combination of factors can cause this abnormal tracking and include the following:

Anatomical defect: 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: The “Q” angle is a medical term used to describe the angle between the hips and knees. The higher the “Q” angle, such as in patients with Knock Knees, the more the quadriceps pull laterally (outwards) on the patella causing misalignment.

Improper Muscle Balance: The quadriceps, the anterior thigh muscles, function to help hold the kneecap in place during movement. Weak thigh muscles can lead to abnormal tracking of the patella, causing it subluxate or dislocate.

Diagnosis of Patellar Maltracking and Instability

Your surgeon diagnoses the condition by collecting your medical history and physical findings. He may also order certain tests such as X-rays, MRI or CT scans to confirm the diagnosis and obtain more detail about the underlying anatomy of the front of the knee.

Treatment of Patellar Maltracking and Instability

Treatment for instability depends on the severity of condition. Initially your surgeon may recommend conservative treatments such as physical therapy, use of braces and orthotics. Pain relieving medications may be prescribed for symptomatic relief. However, when these conservative treatments yield unsatisfactory response surgical correction may be recommended.

The surgery is usually to correct the problem predisposing to the instability. This may be a ligamentous reconstruction of a ligament or a bony procedure to alter the shape of the groove on the front of the femur or the direction of pull of the muscles.

For further information please access the Patient Information booklets – MPFL Reconstruction and Tibial Tubercle Transposition – which are to be found in the Patient Information tab.