The Medial Patellofemoral Ligament (MPFL) is the main soft tissue structure responsible for stabilizing the kneecap (patella) on the inside of the knee. This ligament prevents the patella from shifting too far toward the outside of the leg, a movement known as lateral patellar displacement. When the kneecap dislocates, the MPFL is almost always torn or severely stretched, resulting in patellar instability. MPFL reconstruction uses a tendon graft to create a new ligament, restoring this stabilizing function to resolve the cycle of recurrent kneecap dislocation.
Determining Surgical Necessity
The decision to proceed with MPFL reconstruction surgery is not made after a single dislocation but typically follows a period of failed non-operative management. Initial treatment protocols focus on physical therapy, bracing, and muscle strengthening, particularly the quadriceps. Surgical intervention becomes a strong consideration for patients who have experienced at least two confirmed episodes of patellar dislocation, which is the clinical definition of recurrent instability.
Imaging studies are fundamental in confirming the diagnosis and assessing the underlying anatomy. Magnetic Resonance Imaging (MRI) visualizes the damaged MPFL tissue and evaluates the condition of the articular cartilage. X-rays and specialized CT scans help identify any bony abnormalities that contribute to the instability.
An isolated MPFL reconstruction is often sufficient when the primary cause of instability is a torn or insufficient ligament. However, many patients have structural risk factors that exacerbate the problem, such as a shallow groove on the thigh bone (trochlear dysplasia) or an abnormally high kneecap (patella alta). Another common finding is an increased tibial tubercle-trochlear groove (TT-TG) distance, which measures the lateral pull on the patella.
If the TT-TG distance is significantly elevated, often greater than 15 millimeters, or if other substantial bony abnormalities exist, the surgeon will typically recommend a combined procedure. This may involve a tibial tuberosity osteotomy to correct the angle of pull on the patella or a trochleoplasty to deepen the groove. Addressing these bony issues alongside the MPFL reconstruction is necessary to prevent the new ligament from failing due to excessive mechanical stress. Surgical stabilization is often performed not only to prevent future dislocations but also to protect the articular cartilage from repeated trauma.
Expected Long-Term Outcomes
For appropriate candidates, MPFL reconstruction offers high rates of success in restoring stability. Studies consistently show the procedure is highly effective in preventing future dislocation, with long-term recurrence rates generally reported as low, sometimes around 1.2% to 14% of cases.
The success of the procedure often translates into substantial improvements in a patient’s quality of life and function. Patient-reported outcome measures, such as the Kujala score (which assesses knee function and pain), typically show significant improvement post-surgery, with mean scores often in the mid-80s. This recovery of function allows a high percentage of patients to return to their previous level of physical activity.
A significant majority of active individuals (75% to over 85%) are able to return to sports and high-impact activities after recovery. The reduction in the persistent fear of re-dislocation, known as kinesiophobia, is a psychological benefit that allows patients to move with confidence. By stabilizing the kneecap, the surgery also helps preserve the long-term health of the joint. Repeated dislocations damage the articular cartilage, and preventing this trauma can reduce the risk of developing early-onset arthritis in the patellofemoral joint.
While the outcomes are generally favorable, patients should be aware of potential long-term drawbacks. A small percentage of individuals may experience persistent anterior knee pain, even without further instability. The overall complication rate for MPFL reconstruction is not negligible, with some analyses reporting rates around 26%, which include issues like stiffness or a limited range of motion.
A small number of patients may require a second surgery, either for hardware removal or, less commonly, for a revision procedure due to recurrent instability. The risk of the kneecap becoming “over-constrained,” or too tight, leading to pain or premature wear, can occur if the new ligament is placed or tensioned incorrectly.
Navigating the Recovery Process
The success of MPFL reconstruction relies heavily on the patient’s commitment to the post-operative rehabilitation process, which requires a significant time investment. The recovery is structured into phases, beginning with a period of protection immediately following the surgery. For the first few weeks, the knee is typically protected in a hinged brace, often locked in full extension, to protect the healing graft.
During the initial phase, a patient often uses crutches and is allowed to put weight on the leg as tolerated, but the primary focus is on managing swelling and gently restoring range of motion (ROM), usually limited to 60 degrees of flexion. Dedicated physical therapy (PT) sessions are essential for regaining control of the quadriceps muscle, which often becomes inhibited after injury. Exercises like quad sets and straight leg raises are introduced early to prevent muscle atrophy.
Progression to the intermediate phase, typically from six weeks onward, involves gradually increasing the knee’s ROM and starting more intensive strengthening exercises. The brace is unlocked or removed, and the focus shifts to normalizing walking mechanics and building strength in the surrounding muscles. Full return to running typically occurs around three to four months post-surgery, with a return to full, unrestricted sports participation often taking six to nine months.
Consistent effort is needed over many months to achieve the desired outcomes of physical therapy. Patients must also be aware of the immediate post-operative risks, including a small chance of infection at the surgical site or the formation of a blood clot. Other risks include nerve irritation around the incision or issues related to the surgical hardware, which may occasionally need to be removed in a later procedure.