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Anterior cruciate ligament sprain

Anterior cruciate ligament (ACL) sprain commonly occurs during sport activities that involve complex movements, such as cutting and pivoting. ACL is an intra-articular structure essential for the normal function of the knee. The injury usually results from a sudden deceleration during a high-velocity movement in which a forceful contraction of the quadriceps muscle is required. Injury to the ligament occurs as a result of a valgus stress, hyperextension, and external rotation, as seen when landing from a jump. Moreover, injury may occur with severe internal rotation of the knee or hyperextension with internal rotation. Traumatic injury to the ligament may occur with valgus stress to the knee in association with injury to the medial collateral ligament and the medial meniscus. The ACL may be torn partially or completely. The injury can be of ACL alone or in association with other structures most commonly with a tear of the medial collateral ligament or meniscus.

Anterior cruciate ligament sprain
Anterior cruciate ligament sprain

Individuals usually present with pain, immediate swelling, and limited range of motion. They may give a history of hearing a "pop" In an acute injury, the individual will have severe pain and difficulty with walking. In a chronic injury, a patient may have a history of recurrent episodes of knee instability associated with swelling and limited motion. Patients may describe the "giving way" phenomenon. They may also give a history of a remote injury to the knee that was not rehabilitated.

Physical Examination

  • In the first 12 hours of an acute injury, the athlete will have difficulty bearing weight and will have an effusion.
  • An athlete with an ACL injury is likely to have difficulty achieving full knee extension because the ACL stump gets caught in the notch.
  • Other causes of loss of range of motion (ROM) are a possible associated bucket-handle meniscal tear or loose bony fragment.
  • Examination should begin with inspection to look for an effusion or bony abnormalities.
  • Palpation of the joint line is important to evaluate for meniscal tears or medial collateral ligament (MCL) injuries.
  • Valgus stress testing can be of additional help in evaluating the MCL.
  • Specific tests to determine an ACL tear include the Lachman test, the pivot shift, the anterior drawer test, and the flexion-rotation drawer examination.



Instantly after injury the treatment of an ACL tear includes relative rest, ice, compression, and analgesic or anti-inflammatory medication. Knee immobilizer and crutches are helpful for some patients.

It is vital to establish an accurate diagnosis and the presence of allied injuries, as these might need prompt surgery. These include chondral or osteochondral fractures, meniscal tears, or other injured capsular structures. Commonly in the absence of these other injuries, the acute management will be conservative with early protective rehabilitation.


The rehabilitation of an ACL tear begins as soon as the injury occurs. Rehabilitation management focuses on reducing pain, restoring full motion, correcting muscle strength deficits, achieving muscle balance, and returning the patient to full activity free of symptoms. The rehabilitation program consists of acute, recovery, and functional phases.

Acute phase: This phase focuses on treating tissue injury and clinical signs and symptoms. The goal in this stage should be to allow tissue healing while reducing pain and inflammation. Re-establishment of non-painful range of motion, prevention of muscle atrophy, and maintenance of general fitness should be addressed. This phase lasts from 1 to 2 weeks.

Recovery phase: This phase focuses on obtaining normal passive and active knee motion, improving knee muscle control, achieving normal hamstrings and quadriceps muscle balance, and working on proprioception. Biomechanical and functional shortfalls including inflexibilities and inability to run or jump are addressed. This phase lasts from 2 to 8 weeks after the injury occurs.

Functional phase: This phase should focus on increasing power and endurance of the lower extremities while improving neuromuscular control. Rehabilitation at this stage should work on the entire kinematic chain, addressing specific functional deficits. This program should be continuous with the ultimate goal of prevention of recurrent injury. The functional phase could last for 8 weeks to 6 months after the injury occurs.