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What is an Anterior Cruciate Ligament (ACL) Injury?

Anterior cruciate ligament (ACL) injuries are among the most common traumatic ligamentous injuries sustained in an athletic population. Within the United States alone, there are over 200,000 ACL injuries annually and with increased participation in organized athletics, this number is expected to increase.

The ACL provides stability of the knee in a front to back (anterior to posterior) manner, as well as rotary stability. Loss of knee stability is most commonly described as a recurrent buckling or a ‘giving way’ sensation.

Injury to the ACL can occur by a non-contact (during cutting, pivoting or twisting) or a contact/direct blow mechanism and may result in either a complete or partial disruption of the ligament. ACL injuries in young athletes often require reconstructive surgery to return the athlete to competition, especially in pivoting, twisting sports.


  • Sudden pivot, twist or cut
  • Awkward landings from a jump; either with stiff legs, or knee valgus (knee collapsing inwards)
  • Secondary to blunt force to the outside of the knee, forcing the knee inwards (valgus)

Signs & Symptoms

  • Swollen (effused) knee
  • Often painful injury
  • Oftentimes athletes will note hearing or feeling a “pop”
  • Recurrent ‘giving way’ or sense of instability


Initial treatment for ACL injuries is to reduce the swelling and regain range of motion that is often lost with acute immobilization following injury. Once swelling is normalized, begin to regain range of motion, especially knee extension, focusing on maintaining quadriceps (thigh) activation and strength.

Normally ACL injuries are treated surgically, if the athlete wishes to return to some form of athletics that requires knee stability and rotary movements. Conservative treatment for ACL injuries for young athletes is not commonly recommended due to the likelihood of recurrent injuries, further knee damage, such as meniscus tears, as well as an early onset of arthritis.

Surgical treatment for ACL injuries is recommended to restore the normal function of the knee joint, for those athletes who wish to return to running, cutting, pivoting and twisting maneuvers. The surgery involves reconstructing/replacing the damaged ACL because it cannot heal on its own due to poor blood supply. There are numerous surgical options regarding graft type, which is often discussed with the surgeon who is performing the surgery.

Following ACL reconstruction, the recovery time and time away from organized athletics is about 9-12 months, including all the physical and sports specific preparation done in order to successfully return to sports.

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