The anterolateral ligament (ALL) is a fibrous structure located on the outer side of the human knee joint. It plays a part in maintaining the knee’s stability, particularly during rotational movements. The ligament originates from the lower part of the thigh bone, the lateral epicondyle of the femur, and extends obliquely downward towards the upper shin bone, the tibia. Its position allows it to work with other knee structures for proper joint function.
The Anterolateral Ligament and Its Role
The anterolateral ligament originates slightly proximal and posterior to the lateral epicondyle of the distal femur. It follows an anteroinferior course towards its tibial insertion between the tip of the fibular head and Gerdy’s tubercle below the lateral tibial plateau. This ligament is recognized as a separate structure from the iliotibial band, though it runs parallel to some of its fibers.
The function of the anterolateral ligament is to contribute to the knee’s rotational stability, by limiting internal rotation of the tibia. It becomes taut when the knee is flexed between 30 and 60 degrees, and the tibia is internally rotated. This action helps to control the “pivot shift” phenomenon, which involves abnormal anterior tibial translation and internal rotation laxity, observed in knees with anterior cruciate ligament (ACL) deficiencies. While the anterior cruciate ligament is a contributor to knee stability, the ALL acts as a secondary restraint, augmenting knee protection against vigorous rotation.
When Anterolateral Ligament Reconstruction is Considered
Injuries to the anterolateral ligament occur in conjunction with tears of the anterior cruciate ligament, particularly during twisting activities involving sudden changes in direction or pivoting. Patients experience symptoms such as a feeling of instability or the knee “giving way,” especially during activities that require rotational control. This instability can significantly affect participation in sports and daily movements.
Diagnosis of an ALL injury involves a thorough physical examination, assessing the knee’s stability and range of motion. Specific tests, such as the pivot shift test, can reveal increased rotational laxity, indicating potential damage to the ALL and other anterolateral structures. Imaging techniques, particularly magnetic resonance imaging (MRI), are used to confirm the presence and extent of an ALL tear, and associated injuries to the ACL or other knee components.
Anterolateral ligament reconstruction is considered for patients undergoing ACL reconstruction who present with specific risk factors for continued rotational instability or a higher chance of ACL graft failure. These factors include a high-grade pivot shift observed during examination, participation in high-demand pivoting sports, or a history of a Segond fracture, an avulsion fracture of the lateral tibial condyle associated with ALL injury. Younger patients, those under 20 to 25 years old, and individuals requiring revision ACL reconstruction are also candidates for this combined procedure to improve overall knee stability and reduce the risk of re-injury.
The Reconstruction Procedure
Anterolateral ligament reconstruction is a surgical procedure to replace a damaged ALL, performed alongside an anterior cruciate ligament reconstruction. The surgery involves using a graft, which can be taken from the patient’s own body (autograft) or a deceased donor (allograft). Common autograft choices include a portion of the hamstring tendon, such as the gracilis tendon, for its length and strength.
The procedure is performed using minimally invasive techniques, with small incisions on the outside of the knee over the femur and tibia. The surgeon identifies the attachment points for the new ligament. For instance, the femoral attachment is located slightly proximal and posterior to the lateral epicondyle, while the tibial insertion is on the anterolateral aspect of the proximal tibia, midway between Gerdy’s tubercle and the fibular head.
Once the graft is prepared, tunnels are drilled into the femur and tibia at these specific locations. The graft is then passed through these tunnels, underneath the iliotibial band, and secured with fixation devices such as screws or anchors. The surgeon adjusts the tension of the new ligament, ensuring it provides appropriate rotational stability without over-constraining the knee joint, with the knee in full extension and neutral rotation.
Post-Surgical Recovery and Rehabilitation
Recovery following anterolateral ligament reconstruction, especially when combined with ACL repair, begins immediately after surgery. Patients are advised to keep their leg elevated and use cryotherapy to manage pain and swelling. Initial weight-bearing may be restricted, requiring the use of crutches.
Physical therapy plays a role in the rehabilitation process, starting within the first few days post-operation. Early exercises focus on regaining range of motion, progressing from 0 to 90 degrees of knee flexion within the first four weeks, while emphasizing full knee extension. As healing progresses, around weeks 5 to 12, the focus shifts to more demanding exercises aimed at improving muscle strength, of the quadriceps and hamstrings, and enhancing neuromuscular control.
The timeline for returning to activities varies among individuals, but a gradual progression is followed. Patients may begin light daily activities within a few weeks, while a return to work might be feasible by two weeks if mobility allows. High-impact activities and sports, involving pivoting or cutting, are restricted for at least nine months, and longer, to allow for graft integration and strength recovery. Adherence to a structured rehabilitation protocol, guided by a physical therapist, and meeting specific functional criteria, rather than just time-based milestones, are important for a successful outcome and minimizing re-injury risk.