Patellar (kneecap) instability results from one or more dislocations or partial dislocations. 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 kneecap 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.
Diagnosis
Patients with knee instability may experience different signs and symptoms:
- Pain, especially when standing up from a sitting position
- Feeling of unsteadiness or tendency of the knee to “give way” or “buckle”
- Recurrent subluxation
- Recurrent Dislocation
- 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 because of pressure on nerves and blood vessels.
The surgeon diagnoses the condition by collecting a medical history and physical findings. He may also order certain tests such as X-rays, MRI or CT scans to confirm the diagnosis.
Treatment
Treatment for instability depends on the severity of condition. Conservative treatments may include physical therapy, use of braces and orthotics. Pain relief medications may be prescribed.
When these conservative treatments do not fix the problem surgical correction may be recommended. The surgeon will decide on the surgical procedure based on the type of injury and severity. A lateral retinacular release may be performed where the surgeon releases the tight ligaments on the outside of the patella. This enables the patella to slide more easily in the femoral groove. The surgeon may also perform a procedure to realign the quadriceps mechanism by tightening the tendons on the inside 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. Physical therapy may be recommended for better outcomes and quicker recovery.