Anterior cruciate ligament injury

Last reviewed: 19 Dec 2020

Last updated: 13 Jan 2021

Anterior cruciate ligament injury is typified by a sudden, painful, audible pop noise. The patient is typically unable to return to the ongoing sporting activity, and presents with joint instability, and rapid development of an effusion (hemarthrosis).

Often tender at lateral femoral condyle, lateral tibial plateau, and tibiofemoral joint lines.

A positive Lachman test is most accurate right after the injury and the pivot shift test is more useful in subacute or chronic cases.

History and physical exam usually provide an accurate diagnosis.

X-rays obtained to rule out avulsion fractures or other related conditions, but do not directly identify ACL injury. Magnetic resonance imaging delineates ACL tears, along with associated injury to the menisci and other structures.

Initial treatment for most patients consists of protection, rest, ice, compression, elevation, and analgesia (as appropriate). Subsequent treatment varies by an individual patient's health and fitness status and goals. Treatment may range from minimal or no additional intervention to bracing, physical therapy, and activity modification, and to surgical reconstruction (either early or delayed).

Definition

A torn anterior cruciate ligament (ACL) usually occurs as a result of an acute noncontact deceleration injury, forceful hyperextension, or excessive rotational forces about the knee.[1][2] The ligament may be completely torn, partially torn, or avulsed from its origin or insertion. The ACL is the primary restraint to excessive anterior translation and rotation of the tibia on the femur; therefore, complete ACL disruption typically results in dynamic knee instability or the inability to respond to quick changes in position.[3]