There are approximately 100,000 to 200,000 ACL ruptures per year in the United States alone. These injuries are common in professional and recreational athletes across multiple different sports. ACL injury may place that athlete at risk for developing arthritis in the future. The majority of athletes elect to undergo ACL reconstruction (ACLR) secondary to their goal to maintain the ability to engage in athletic endeavors, however, others choose non-operative care.
About 50% of those who suffer ACL injury also sustain an addition injury to their meniscus, cartilage or other ligaments about the knee. A thorough work-up is crucial to ensure the extent of injury sustained.
ACL injury is more common females (~4-5 to 1), and females often sustain ACL injuries at a younger age. Research has taught us that jump-landing mechanics have a role in causing ACL injuries, particularly in young, adolescent athletes. At present time, ACL injury prevention programs focus on neuromuscular training and plyometric activities – which we perform via our COSMO Fit Lab – to address landing mechanics and uncover muscle weakness and imbalances.
The ACL provides the majority of the knee’s effort to prevent anterior (forward) translation of the tibia relative to the femur. The ACL also acts as a secondary restraint to rotation of the tibia and varus/valgus stress. The ACL is essential to knee stability, ensuring the tibia does not rotate internally about the femur. At the time of injury, the athlete is often planting their foot and pivoting or twisting; this injury is commonly non-contact in nature. The knee partially dislocates, which results in the pathognomonic bone bruising seen on MRI.
Individuals may describe an audible “pop” at the time of injury, then immediate onset of pain, swelling and difficulty with weight bearing. Not everyone has this dramatic of a presentation, others have more vague symptoms of pain, swelling and a feeling of mild instability with pivoting and twisting. On exam, we assess your range of motion (how much you can bend and extend), the symmetry of your ligaments in a side to side comparison of both knees, including a Lachman test.
Lachman Test: this clinical test is used to evaluate the integrity of the ACL. With the knee bent to 30 degrees of flexion, the femur is stabilized while the examiner applies an anterior directed force to the tibia. If the knee is ACL-deficient, the tibia will move forward in relation to the femur excessively.
Varus and Valgus Stress Test: this clinical test is used to evaluate the integrity of the lateral collateral ligament (LCL) and medial collateral ligament (MCL), respectively. The knee is held in 20 degrees of flexion and loaded in varus or valgus distally such that the LCL or MCL is placed on stretch. The examiner assesses the amount of opening/gapping at the lateral (varus) and medial (valgus) joint space. The test is repeated with the knee in full extension.
Pivot Shift Test: This clinical test is used to evaluate for an ACL rupture. It may be difficult to perform in clinic due to pain/muscular guarding; however, it may be performed in the operating room under anesthesia. With the patient lying on their back, the affected knee is fully extended with the tibia internally rotated. The examiner then applies a coupled valgus and internal rotation force while flexing the knee. An appreciable “clunk” is felt at approximately 30 degrees of knee flexion if the ACL is torn.
X-rays are evaluated for alignment, the presence of degenerative changes at the joint, for fracture or an avulsion injury. MRI is also performed to assess the integrity of the ACL and for additional injuries to the meniscus, cartilage and ligaments, such as the MCL, LCL or PCL (posterior cruciate ligament).
The torn ACL is reconstructed with a new ACL graft. Both ACL surgical technique and graft selection have undergone immense research in the orthopaedic surgery literature. Many factors including age, activity level, sex and patient interests influence the graft choice. Dr. Logan uses both patellar tendon and quadriceps autograft (the patient’s own tissue) techniques during ACL reconstruction surgery. The final graft choice is based on a discussion between our physicians and the patient. Allografts may be considered in patients of certain age and activity groups.