Rehabilitation for Anterior Cruciate Ligament Injury

Updated: Jan 26, 2023
  • Author: Tarek O Souryal, MD; Chief Editor: Stephen Kishner, MD, MHA  more...
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Practice Essentials

The anterior cruciate ligament (ACL) originates from the tibial plateau just medial and anterior to the tibial eminence. The ACL tracts from the tibia superiorly, laterally, and posteriorly, to its insertion on the posterior aspect of the medial wall of the lateral femoral condyle. The ACL is composed of 2 bundles, the anteromedial bundle and the posterolateral bundle. The ACL provides 85% of the total restraining force to anterior translation of the tibia. An ACL tear is a common injury that occurs in all types of sports. This injury usually occurs during a sudden cut or deceleration, as it typically is a noncontact injury. The patient may state, "I planted, twisted, and then heard a pop." Before the advent of arthroscopic knee surgery in the early 1970s, ACL tear was often a career-ending injury.

Workup in anterior cruciate ligament injury

Magnetic resonance imaging (MRI) of the knee usually is recommended prior to surgery for evaluation of the other ligaments and the menisci, because findings can influence the treatment plan.

Radiographs may demonstrate an avulsed fragment just lateral to the tibial plateau.

The presence of fat globules found in aspiration of a hemarthrosis suggests an intra-articular fracture.

Management of anterior cruciate ligament injury

For complete rupture, no local healing response is detectable at the injury site, and a graft must be used to replace the ACL. [1] Options include the use of autografts employing the central one third of the patellar tendon (considered a bone-tendon-bone graft), the quadruple semitendinosus/gracilis tendon, or the quadriceps tendon. [2, 3] A cadaveric allograft may also be used.

During physical therapy, passive motion is emphasized, with active flexion and assisted extension in the sitting or prone position to ensure good leg control (ie, ability to flex the hip and lift the leg against gravity without assistance). A continuous passive motion machine can be used to establish 0-30° of motion immediately postoperatively and to progress to 60° of knee flexion by the morning following surgery.

The patient then begins gait training with crutches (weight bearing as tolerated), with the knee in an immobilizer. The patient usually can be discharged on the first postoperative day and should be encouraged to avoid crowds, keep the leg elevated when not ambulating, use the crutches at all times for protection, and continue frequent icing.

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Anterior Cruciate Ligament Injury [Sports Medicine]

Anterior Cruciate Ligament Pathology

Anterior Cruciate Ligament (ACL) MRI



Like all ligaments, the anterior cruciate ligament (ACL) is composed of type I collagen. The ultrastructure of a ligament is close to that of tendons, but the fibers in a ligament are more variable and have a higher elastin content. Ligaments receive their blood supply from their insertion sites. The vascularity within a ligament is uniform, and each ligament contains mechanoreceptors and free nerve endings that are hypothesized to aid in stabilizing the joint. Avulsion of ligaments generally occurs between the unmineralized and mineralized fibrocartilage layers. The more common ACL tear, however, is a midsubstance tear. This type of tear occurs primarily as the ligament is transected by the pivoting lateral femoral condyle.




United States

Epidemiologic studies estimate that approximately 1 in 3000 individuals sustains an ACL injury each year in the United States. This figure corresponds to an overall injury rate approaching 200,000 injuries annually. [4] This estimate is low for women, because ACL injury rates are estimated to be 2-8 times higher in women than in men participating in the same sports.


In a study of 101,125 ACL reconstructions in Denmark, Luxembourg, Norway, Sweden, the United Kingdom, and the United States, Prentice et al found that soccer injuries were the most common cause of these procedures, with the rate ranging from 14.1-42.3%. [5]


Not a single report of mortality was found in 6 different studies examining the morbidity and mortality of anterior cruciate ligament repair. The total number of patients in these combined studies was 363. Morbidity was divided into 5 classes. The first class included patients who were symptomatic with activities of daily living (ADL). The second class included patients who were able to perform all ADL. Patients in the third class were able to perform mildly stressful sports (eg, jogging, swimming, biking, cross-country skiing). The fourth class included patients who were able to perform moderately stressful sports, including baseball, alpine skiing, racquet sports, dance, and lacrosse. The last class included patients who returned to perfect health and were capable of performing very stressful sports, such as soccer, basketball, football/rugby, volleyball, gymnastics, and hockey. Postsurgery status of patients was as follows:

  • Remained class 1 - 3.3%

  • Remained class 2 - 1.4%

  • Attained class 3 - 11.8%

  • Attained class 4 - 17%

  • Returned to class 5 - 66.5%


No known correlation exists between race and occurrence of ACL injuries.


According to numerous studies, female athletes sustain a greater number of anterior cruciate ligament (ACL) injuries than do male athletes. These results are well supported in 2 different papers. The first paper, by Arendt and Dick, showed that female athletes sustained significantly higher incidences of ACL injuries than their male counterparts did when competing in collegiate soccer and basketball. [6] The authors' data demonstrated that women have a 2.4 and a 4.1 times greater chance of incurring ACL injury when compared with males in soccer and basketball, respectively. A second paper, by Hutchinson and Ireland, reported that female athletes competing in the 1988 Olympic basketball trials sustained 81% of ACL injuries during the trials. [7]


Anterior cruciate ligament injuries occur most commonly in individuals aged 14-29 years. These years correspond to a high degree of athletic activity.