Anterior cruciate ligament injury

Anterior cruciate ligament (ACL) injury is typified by a palpable or audible pop noise. Patients experience pain, joint instability, and rapid development of hemarthrosis. If the injury occurs during a sporting activity, they are typically unable to return to play.

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

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

History and physical exam usually provide an accurate diagnosis.

X-rays are 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. 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).

A torn ACL usually occurs as a result of an acute noncontact deceleration injury, forceful hyperextension, or excessive rotational forces about the knee.[1]Boden BP, Dean GS, Feagin JA, et al. Mechanisms of anterior cruciate ligament injury. Orthopedics. 2000;23:573-58. http://www.ncbi.nlm.nih.gov/pubmed/10875418?tool=bestpractice.com [2]Ettlinger CF, Johnson RJ, Shealy JE. A method to help reduce the risk of serious knee sprains incurred in alpine skiing. Am J Sports Med. 1995;23:531-37. http://www.ncbi.nlm.nih.gov/pubmed/8526266?tool=bestpractice.com ​ 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]Butler DL, Noyes FR, Grood ES. Ligamentous restraints to anterior-posterior drawer in the human knee: a biomechanical study. J Bone Joint Surg Am. 1980;62:259-70. http://www.ncbi.nlm.nih.gov/pubmed/7358757?tool=bestpractice.com