Patellar (knee cap) instability results from one or more dislocations or partial dislocations (subluxations). 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 stretching 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 damage the underlying soft structures such as muscles and ligaments that hold the knee cap in place. Once damaged, these soft structures are unable to keep the patella (knee cap) in position. Repeated subluxation or dislocation makes the knee unstable and the condition is called as knee instability.
Patients with knee instability experience different signs and symptoms such as:
Various factors and conditions may cause patellar instability. Often a combination of factors can cause this abnormal tracking and include the following:
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.
Treatment for instability depends on the severity of condition and based on the diagnostic reports. 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.
Considering the type and severity of injury surgeon decides on the surgical correction. A lateral retinacular release may be performed where your surgeon releases, or cuts, the tight ligaments on the lateral side (outside) of the patella enabling the patella to slide more easily in the femoral groove.
Your surgeon may also perform a procedure to realign the quadriceps mechanism by tightening the tendons on the inside or medial side of the knee.
If the misalignment is severe tibial tubercle transfer (TTT) will be performed. This procedure involves the surgeon removing a section of bone where the patellar tendon attaches on the tibia. The bony section is then shifted and properly realigned with the patella and reattached to the tibia with two screws.