Medial Patellofemoral Ligament (MPFL) reconstruction stabilizes the kneecap (patella). This procedure addresses chronic patellar instability, which occurs when the kneecap repeatedly slips out of its normal position. The primary goal is to restore the natural restraint that prevents the patella from dislocating toward the outside of the knee joint. By replacing the damaged ligament with a new tissue graft, the surgery returns the patellofemoral joint to a state of smooth, functional alignment.
The Role of the MPFL in Knee Stability
The MPFL is a thin, flat band of tissue on the inner (medial) side of the knee that connects the patella to the femur. It is the most significant soft tissue structure responsible for keeping the kneecap centered within the trochlear groove of the femur. Biomechanical studies estimate that the MPFL resists over 50% of the force that would otherwise cause the patella to move laterally. It functions like a passive checkrein, becoming taut when the knee is extended or when the patella begins to shift outward.
This ligament is frequently torn or permanently stretched during a traumatic patellar dislocation. Once compromised, the MPFL often heals in an elongated, non-functional state, failing to provide the necessary restraint. This failure leads to chronic patellofemoral instability, characterized by recurrent dislocations. While acute injury is a common cause, some patients have underlying anatomical factors, such as trochlear dysplasia or patella alta, that predispose them to instability. Reconstruction is the preferred treatment when non-operative management fails and chronic instability impacts daily activities.
Steps of the Reconstruction Procedure
MPFL reconstruction involves replacing the non-functional native ligament with a strong tendon graft, rather than attempting a direct repair. The graft is most commonly harvested from the patient’s own hamstring tendons (autograft), though a donor tendon (allograft) can also be utilized. This tendon is prepared into a double-stranded structure that mimics the size and strength of the original MPFL.
The procedure begins with the creation of small bone tunnels, or sockets, in the patella and the femur, which serve as the attachment points for the new ligament. On the patella, two short tunnels are typically drilled on the medial edge, positioned near the junction of the upper and middle thirds of the kneecap. A single femoral tunnel is then drilled on the medial side of the thigh bone at a specific location known as Schöttle’s point, which marks the anatomic insertion site of the MPFL.
The prepared tendon graft is passed through the patellar tunnels and routed beneath the soft tissues to the femoral tunnel site. Securing the graft at the correct tension is a precise step to avoid over-constraining the joint or leaving it too loose. Surgeons check for “isometry,” ensuring the graft maintains relatively equal tension throughout the knee’s range of motion, especially when the knee is flexed to about 30 degrees. The graft is firmly secured in the bone tunnels using specialized hardware, such as bioabsorbable screws or anchors, creating a new ligament to prevent lateral patellar movement.
Post-Operative Recovery and Rehabilitation
The recovery process following MPFL reconstruction is highly dependent on a structured and prolonged physical therapy program. Immediately after surgery, the patient’s leg is placed in a brace, often locked in full extension, and crutches are used to limit weight-bearing for the first few weeks. The initial focus of physical therapy in the first two weeks is on pain and swelling management, as well as regaining full knee extension and achieving a controlled range of motion.
Between three and six weeks, the brace is typically unlocked or discontinued, and weight-bearing progresses to tolerance as the patient begins gentle strengthening exercises for the surrounding musculature. The intermediate phase, from seven to twelve weeks, shifts to more advanced strengthening, balance training, and functional activities to restore the knee’s stability and mobility. Adherence to the prescribed rehabilitation protocol is paramount, as the graft needs time to biologically incorporate into the bone tunnels.
Return to high-impact activities and sports is a gradual process that usually occurs in the later stages of recovery. Patients can typically return to light activities and work within three to five months, provided they meet specific strength and functional criteria. A full return to competitive sports or physically demanding work is generally expected to take nine to twelve months, though this timeline varies based on individual healing rates and any additional procedures performed.