Most patients with an ACL injury will give a history of acute trauma. Patients often report hearing a “pop” at the time of injury. Often this will be a noncontact injury during a deceleration and rotation maneuver. Patients generally are unable to continue their activity, develop a hemarthrosis within 24 hours, and seek medical attention. Patients with a chronic ACL tear will often give a history of recurrent episodes of instability, especially with cutting or pivoting activities.

On examination, an effusion will usually be present. This may not be the case during an initial on-field examination or in chronic cases. A Lachman test will reveal increased anterior translation with no firm end point. This examination should be performed on both knees for comparison. The pivot shift test will reveal a greater shift in the ACL injured knee compared with the contralateral normal knee, but muscle spasm may impair the examination.

A complete knee examination should be performed as many associated injuries may also be present. Evaluation of the collateral ligaments, posterolateral corner, posterior cruciate ligament (PCL), and menisci is important. Particularly in chronic or revision cases, an evaluation of limb alignment should be performed, as undiagnosed malalignment is a potential cause of failure of reconstruction.

Patients with a suspected ACL injury should initially be evaluated with a series of plain radiographs. Although these will generally be normal, they are useful in ruling out fracture in the setting of an acute injury with hemarthrosis. A Segond fracture, a small bony avulsion of the lateral tibial plateau, can sometimes be seen and is strongly associated with ACL injury. Generally, anteroposterior (AP), lateral, and sunrise views are sufficient in the case of an acutely injured knee. In cases of chronic ACL tears or in revision cases, the surgeon should be alert to the possibility of malalignment and full-length standing films of both lower extremities should be evaluated if malalignment is suspected.

CT scan does not have a major role in cases of acute ACL injury, but it may be helpful in revision cases to accurately identify tunnel positions and possible tunnel widening.

MRI is the most useful imaging modality for diagnosis of ACL injury. The torn ACL is usually identified by the interruption of the fibers and the abnormal horizontal alignment of the ligament. Associated injuries, including meniscal tears, chondral injuries, and ligamentous injuries, can also be identified. In over 80% of patients, a bone bruise will be identified, usually in the lateral compartment. If these bone bruises are absent, the clinician may suspect the injury is chronic or the possibility of another injury.

Treatment for ACL tears should be individualized to the patient. In general, ACL reconstruction allows a return to sports and other activities that require cutting and pivoting. For some patients, especially older patients that do not participate in these activities, a nonoperative approach may be the preferred treatment. Certainly, a trial of nonoperative treatment, consisting of physical therapy and a gradual return to activity, is appropriate for the older, low-demand patient. If this patient has instability during their normal activities after completing a rehabilitation program, at that point they would be a candidate for ACL reconstruction. The decision to undergo ACL reconstruction should be individualized after a thoughtful discussion between the surgeon and the patient regarding the risks, benefits, and expected outcomes of the procedure.

Operative treatment should be offered to all patients who desire to return to cutting or pivoting athletic activities. An ACL tear is a season-ending injury and allowing an athlete to return to competition with an unstable knee exposes the patient to a significant risk of meniscal and chondral injury that could likely be avoided by ACL reconstruction.

Timing of ACL reconstruction has received attention in the sports medicine literature with some conflicting reports as to when it is safe to perform ACL reconstruction after an injury. It is important to assess the “personality” of the knee injury and to recognize the large variation among patients. Prior to performing ACL reconstruction, the knee effusion and swelling should have largely resolved, and the range of motion, particularly extension, should be regained. A strong quadriceps contraction is critical to the return of full extension and some patients have severe quadriceps inhibition with this injury. There is a rare patient who will have an impinging torn ACL that requires debridement in a separate arthroscopic procedure to facilitate the return of
full extension. A continuous passive motion (CPM) machine can also be helpful in rare cases where loss of flexion and parapatellar fibrosis limits flexion. If patients are progressing slowly with their recovery prior to surgery, reconstruction may be delayed for a period of weeks to allow the soft tissues around the knee to recover.

Our preferred technique is an anatomic single-bundle reconstruction with independent drilling of the tibial and femoral tunnels. Based on the clinical situation, either autograft (either hamstring or patellar tendon) or an allograft (usually tibialis anterior tendon) may be used. The decision on graft is based on patient preference, but a patellar tendon graft is preferred for very unstable knees or in a young athlete with a strong quadriceps who plays the most demanding sports. Allografts are used when an early return to daily activities is important and the demands on the knee are less. Hamstring grafts are used for competitive and recreational athletes who prefer autograft and may not rehabilitate well with the disability of a patellar tendon autograft harvest. The same anatomic single-bundle technique can be used regardless of graft choice.

A standard operating table is used with the foot of the bed left extended. A leg holder is not used as it often prevents adequate flexion of the knee when drilling through the anteromedial portal. Instead, we use three posts to support the operative leg in either 90° or full flexion (Fig. 70.1A,B). A vertical post is placed on the lateral side of the thigh to allow access to the medial compartment as well as to prevent hip abduction when the knee is flexed. Two posts are placed across the bed to serve as footrests to maintain the two flexion angles most often needed during the procedure (90° and >125°). This setup allows the knee to be held in either position without any assistance, which frees the hands of both the surgeon and the assistant. Regardless of the setup, if an anteromedial portal drilling technique will be used, it is essential that the knee can be flexed adequately.