ACL Tear, Repair & Revision

The anterior cruciate ligament (ACL) is one of four main rope-like structures that stabilize the knee joint by connecting the femur (thigh bone) to the tibia and fibula (leg bones). The ACL specifically prevents anterior translation (forward movement) and internal rotation of the tibia relative to the femur. The ACL stabilizes the knee during planting, jumping, landing, stopping, cutting, and pivoting maneuvers. The ACL is one of the most commonly injured structures of the knee in young competitive athletes.

The ACL is most often torn by a non-contact mechanism when an athlete attempts to plant, jump, land, stop, cut, or pivot on a single leg. Contact injuries can also occur when the knee sustains a direct blow, but this is less common.  ACL injuries also occur during skiing with possibly a different mechanism.

When an athlete tears their ACL, they often perceive a “pop” while planting on a single leg during an athletic maneuver.  The degree of initial pain is variable but most athletes are unable to continue playing.  Swelling is often delayed but typically occurs within hours of the injury. Swelling and pain often make it difficult to walk after the initial injury. Returning to play following the injury risks further injury to the meniscus, cartilage, and other structures.  Without surgery, patients often experience continued episodes of instability and giving way.

An ACL tear is diagnosed with a combination of patient history of the mechanism of injury and physical exam.  X-rays and Magnetic Resonance Imaging (MRI) help confirm an ACL tear and determine if there are other associated injuries including fractures and other ligament, meniscal or cartilage tears. Most often, the history involves a younger competitive athlete (females more common than males) who report injuring their knee.  They are usually unable to continue playing and experience pain, swelling, and difficulty bearing weight.  On physical exam, Dr. Chudik will check for the presence of an effusion (swelling in the knee), loss of knee range of motion, inability of the quadriceps to properly contract, and perform a ligament exam including a Lachman exam. The Lachman exam specifically tests the function of the ACL and is positive when the tibia is able to be pulled forward relative to the femur without a perceptible endpoint provided by an intact ACL.

An MRI is ordered which confirms the suspected ACL tear and reveals the extent of tearing and possible injury to other surrounding structures.

The majority of ACL tears are functionally complete which prevents athletes, even recreational ones, from returning to athletic activities due to knee instability and giving way.  Additionally, attempting to return to activities without an ACL risks further injury to the meniscus and cartilage of the knee with any single instability episode. Living without an ACL places increased stress on the meniscus of the knee and can lead to break down and tears of the meniscus without returning to risky sport activities.  Therefore, most patients choose to have surgery to reconstruct their ACL. Pediatric patients with open growth plates sometimes require surgery that avoids injury to their growth plate as non-operative treatment has been shown to result in continued instability, meniscus tears, and further damage to the knee.

Surgery to repair the ACL is not as reliable reconstructing (replacing) the ACL using a tendon graft.  There are several autologous (from the patient) graft options including bone-patellar tendon-bone, hamstring, quadriceps, and iliotibial band. Dr. Chudik prefers not to use allogenic tendon graft (allografts) from cadavers which have been shown to result in higher rates of re-tear.  Surgery can be performed after the swelling and range of motion are restored for the injured knee which generally requires 2 to 3 weeks of physical therapy following the injury. During ACL surgery, the torn ligament is reconstructed (replaced) with a tendon graft because the ligament is damaged such that a simple repair is often not successful. The goals of the surgery are to reconstruct the torn ligament, repair any other damaged structures (including other ligaments, the meniscus, and cartilage) and restore function and stability to the knee.

• The surgery is typically performed as an outpatient procedure (patient goes home the same day after surgery) with lighter general anesthesia and an adductor and possibly an IPACK nerve block to numb the knee.
• A patient can expect to be on crutches and partial weight bearing for approximately 4 weeks following an isolated ACL reconstruction to protect the graft.
• A post-op knee brace is worn for only 24 hours to ambulate while the nerve block is working and used to help keep the knee straight at night while sleeping.
• If the meniscus is also repaired during surgery, the patient will use crutches and wear a brace locked in full extension (straight) for 6 weeks.
• The brace may also be needed if other ligaments required surgery as well but this is typically known from the MRI.
• Following surgery, the incisions should be kept clean and dry for the first 14 days after surgery. Showering lightly is allowed after 2 weeks but wounds cannot be submerged underwater for at least 3 weeks after surgery.
• A patient may drive after 6 weeks if the driving right lower extremity is involved.
• Home exercises focusing on straightening the knee and contracting the quadriceps muscles begin immediately in the recovery room and are performed on an hourly basis.
• Physical therapy begins days after surgery and will be required to restore motion, strength, and proprioception (balance) following reconstruction.
• Strengthening, biking, and range of motion exercises are emphasized and prolonged walking and standing are discouraged during the first three months following surgery.
• Prolonged immobilization associated with sitting, driving, and flying are avoided for the first six weeks following surgery to prevent deep vein thrombosis (DVT)(clot) formation.
• Recovery varies from 6 to 12 months depending on the injury and the patient.

A patient may return to school or sedentary work in just less than 1 week if the patient can use crutches, elevate the extremity, perform their exercises frequently, and get up and move around regularly to avoid deep vein thrombus (DVT) (clot) formation.

After the knee is fully rehabilitated and physical therapy is completed, Dr. Chudik recommends competitive athletes participate in a 6 week return to sport training program and also pass Dr. Chudik’s ACL Return to Sport Test to ensure the athlete is safe to return to sport.  The test is performed to confirm that the knee is fully rehabilitated and more importantly, to confirm that errors in movement patterns known to put patients at risk for re-injury are corrected. Timelines for return to sport vary depending on the patient, the extent of the injury, and the sport. A full return to sports participation can take anywhere from 6 to 12 months.

ACL reconstructed knees generally perform well over our athletic lifetime, especially when maintained with an appropriate regimen of strength training, flexibility, and activity.  More importantly, non-impact activities such as biking, or water sports usually provide optimal fitness to the knee without overdoing it. It is important to remember that any bone or joint with a history of injury such as an ACL tear is more susceptible to an early onset of arthritis.