Patellar Instability

The patella acts like a pulley, improving the leverage of the quadriceps muscle to extend the leg. It sits within the trochlear groove at the lower end of the femur and connects to the quadriceps tendon above and the patellar tendon below.

Several structures help keep the kneecap centered during movement:

• The trochlear groove, which provides a bony track.
• The medial patellofemoral ligament (MPFL), a soft-tissue band that anchors the inner edge of the patella to the femur.
• The quadriceps muscles, which guide the patella during knee motion.

If any of these structures are weak, damaged, or anatomically shallow, the patella can slide out of place, particularly during twisting or cutting movements.

Patellar dislocation accounts for 2–3% of all knee injuries, with the highest incidence in teenagers and young adults, especially females and athletes involved in sports that require sudden direction changes—such as basketball, soccer, and gymnastics.

Once a person experiences a first-time dislocation, the chance of recurrence can range from 20% to over 50%, depending on age, activity level, and anatomy.

Certain factors increase the risk of instability, including:

• Shallow trochlear groove (trochlear dysplasia)
• Patella alta (a high-riding kneecap)
• Weak quadriceps muscles
• Increased Q-angle (wider pelvis-to-knee angle)
• Generalized ligamentous laxity or hypermobility
• Previous knee trauma or surgery

Diagnosis begins with a careful history and examination. Dr. José Vega, Cleveland’s trusted knee and sports medicine specialist, will ask about how the injury occurred, any prior episodes of dislocation, and your current symptoms.

Common symptoms include:

• Feeling the kneecap “pop out” or “slide” to the side
• Pain and swelling in the front or inner knee
• Difficulty bending or straightening the leg
• A feeling of weakness, giving way, or lack of trust in the knee

During the exam, Dr. Vega will assess patellar tracking, muscle strength, and ligament stability. Specific tests, such as the apprehension test, can help reproduce the feeling of instability when the patella is gently moved laterally.

Imaging studies are often performed to confirm the diagnosis and identify contributing anatomical factors:

• X-rays show the position of the patella and can detect fractures or alignment issues.
• MRI evaluates the soft tissues, including MPFL tears, cartilage injury, and trochlear shape.
• CT scans may be used for surgical planning in complex or recurrent cases.

Treatment depends on the severity of the instability, the number of dislocations, and the patient’s activity level.

Nonsurgical Treatment

For first-time dislocations or mild instability, non-operative care is often successful. It may include:

• Immobilization or bracing for a short period to allow tissues to heal.
• Physical therapy focusing on strengthening the quadriceps—especially the vastus medialis oblique (VMO)—to improve patellar tracking.
• Balance and proprioception training to improve knee control.
• Activity modification to avoid deep squats or twisting movements during early recovery.

With proper rehabilitation, many patients regain normal function and avoid recurrence.

Surgical Treatment

Surgery may be recommended for patients with recurrent dislocations, significant pain, or structural abnormalities contributing to instability.

Common procedures include:

• Medial Patellofemoral Ligament (MPFL) Reconstruction: Rebuilds the main soft-tissue stabilizer of the kneecap using a small tendon graft. This is the most common procedure for recurrent instability.
• Tibial Tubercle Osteotomy (TTO): Realigns the patellar tendon attachment on the tibia to improve kneecap tracking and reduce lateral pull.
• Trochleoplasty: Performed in select cases with severe trochlear dysplasia, this procedure deepens the groove to better contain the patella.

These procedures can be combined to correct both soft-tissue and bony causes of instability. Most are performed arthroscopically or through small incisions.

Rehabilitation after surgery includes progressive motion, muscle strengthening, and gradual return to sports—typically around 4–6 months, depending on the procedure and patient progress.

While some anatomic factors can’t be changed, the risk of instability can be reduced with proper conditioning and movement training:

• Strengthen the quadriceps, hips, and core to control knee alignment.
• Focus on flexibility, particularly in the hamstrings and IT band.
• Practice safe landing and cutting techniques to minimize lateral stress on the knee.
• Use supportive braces or taping if recommended after a prior dislocation.
• Address early symptoms such as patellar tracking pain before instability progresses.