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MPFL Reconstruction – Patellar Instability


Patellar instability is a common and recurrent problem that is most prevalent in the young athletic population. Patellar instability is a condition that occurs when the kneecap or patella is either dislocated, a complete displacement from the patella’s normal positioning, or subluxed, a partial dislocation. Dislocation can occur from an acute trauma like a blow to the knee, but can also become a chronic or recurrent injury. Anatomical positioning of the patella as well as gender differences can influence and predispose an individual to patellar instability. Patellar instability is associated with injury to the MPFL or medial patella femoral ligament but can involve other ligaments, bones, or cartilage damage.


The MPFL is a ligament on the inside of the knee that stabilizes your patella (kneecap). The patella glides smoothly in a groove of the femur called the trochlea held in place by ligaments and tendons, including the MPFL. The patella is the attachment site for the quadriceps tendon and patellar tendon, which allows you to bend and straighten your leg. When a patient experiences a dislocation or subluxation to the knee, the ligaments and tendons surrounding the patella can become stretched or torn and thus are weakened leading to a greater risk of recurrent dislocations and instability.

Quadriceps. femoris muscle. Tendon of. quadriceps. femoris muscle. Patella. Medial patellar. retinaculum. Lateral patellar. retinaculum. Tibial collateral. ligament. Fibular. collateral. ligament. Patellar ligament. Fibula. Tibia. (c) Anterior view of right knee. Figure 8.8c.

Clinical Evaluation

Diagnosis of MPFL injuries is often made clinically along with a thorough history. However, X-rays and magnetic imaging studies (MRI) can also be helpful in confirming the diagnosis.


Initial Management

Once an injury is sustained treatment is focused on obtaining a full range of motion of the knee and allowing the swelling to subside. This can often occur within the first week to ten days but can take as long as 6 weeks in the cases of associated injuries. Once this occurs both conservative and operative treatment options can be exercised.

Non-Operative Treatment

Conservative treatment is often recommended for patients who have had an initial isolated dislocation without other ligament or cartilage damage. Treatment includes immobilization of the knee with rest followed by subsequent physical therapy to strengthen the surrounding muscles. It is an effective form of treatment for those not experiencing instability from normal activities or for older, less active patients. In patients where stability is not obtained after a thorough rehabilitation program, surgical reconstruction offers an alternative in preventing recurrent instability and return to function. Often a 3 month program is needed to fully assess success of conservative treatment.

Operative Treatment

Surgery is recommended in patients with recurrent patellar instability or a history of multiple dislocations. Surgical management of MPFL injuries involves reconstruction of the ligament. A knee arthroscopy will also be performed at the time of surgery to evaluate and treat damage to the patella as well as any other injuries. Surgery is typically performed after knee motion has returned and swelling has dissipated. Reconstruction is performed using either a hamstring autograft, which is the patient’s own tissue harvested at the time of surgery, or an allograft, which is donor tissue from a cadaver. The goal of this procedure is for the patient to successfully return to full athletic activity with no recurrent instability at 6 – 9 months. A general guideline of MPFL rehabilitation can be found within the Rehabilitation Protocols. As each case differs, treatment results and expectations will be discussed with the surgeon prior to surgery.

Download a PDF of this information.

Download the physical therapy protocol for this condition.

mpfl recon