Rehabilitation for Anterior Cruciate Ligament Injury

Updated: Mar 01, 2016
  • Author: Tarek O Souryal, MD; Chief Editor: Consuelo T Lorenzo, MD  more...
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Overview

Background

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.

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Pathophysiology

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.

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Epidemiology

Frequency

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. [1] 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. The average cost for surgical repair of an ACL tear is approximately $11,500. If all ACL injuries were repaired, the associated expenditure for 100,000 procedures would eclipse $2 billion annually.

Mortality/Morbidity

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%

Race

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

Sex

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. [2] 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. [3]

Age

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

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