ACL injury.

The picture presents Jakub Błaszczykowski, a polish midfielder playing for Borussia Dortmund football club. He has recently ruptured his ACL which means that we will not see this talented player for the rest of current season. The anterior cruciate ligament (ACL) is one of the most commonly injured ligaments of the knee. The post will cover current concepts in regards to the causes, history, risk factors, diagnosis and treatment of the ACL tear.
ACL injury occurs as a result of a lack of stability provided by the dynamic and passive stability mechanisms of the knee. ACL injuries occur most frequently in non-contact situations with the athlete in single foot stance, forceful valgus knee collapse with knee close to full extension accompanied with external or internal rotation of the tibia (in situation involving landing, deceleration or rapid change of direction).  Athletes participating in football (soccer), basketball, handball and skiing are most commonly affected.  
Commonly cited in the literature risk factors may include female sex, decreased intercondylar femoral notch size, decreased depth of concavity of the medial tibial plateau, increased slope of the tibial plateaus, increased anterior-posterior knee laxity, prior reconstruction of the ACL, familial predisposition, muscle imbalances (quad dominant), increased knee adduction moment, hormonal and genetic factors as well as extrinsic factors such as weather, type and condition of playing surface, and footwear. These risk factors most likely act in combination to influence the risk of suffering ACL injury. 
With an acute injury, the patient often describes that they heard a loud pop and then developed intense pain in the knee. The knee joint will begin to swell within a few hours because of bleeding within the joint. Later, patient may complain of recurrent pain and swelling and giving way episodes. 
Physical examination includes the Lachman test, the pivot-shift test, and the anterior drawer test. Plain X-rays of the knee may be done looking for broken bones (especially in children). MRI has become the test of choice to image the ACL rupture.  
Existing treatment options are directed to avoid subsequent lesions to the meniscus and/or cartilage and prevent from early knee osteoarthritis development. ACL tear may be treated by non – surgical methods or by operative procedure. Nonsurgical treatment may be appropriate for patients who are less active, do not participate in activities that require running, jumping, or pivoting. In this case, conservative treatment usually incorporates physical therapy and exercise rehabilitation to return strength, range of motion and neuromuscular control.  The other option is usually reserved for active patients and pro athletes who require full knee stability during their sports activity. ACL reconstruction is performed and most commonly, an autograft (hamstring or patellar tendon) is used to reconstruct the ACL. Also, allograft is an option although it has been recently shown to be a significant predictive factor for subsequent ACL injury.