Which of the following occurs in athlete with a torn ACL ?

The anterior cruciate ligament (ACL) is one of the major knee joint ligaments in humans, and damage to this ligament is fairly common in athletes. An ACL tear is most often a sports-related injury but can also result from accidents, falls, and work-related injuries. Most sports-related ACL tears occur when a person pivots or lands from a jump.

Based on this information as well as your knowledge of ligaments, which of the following occurs in an athlete who has a torn ACL?

 Rapid firing of all the neurons involved in the affected motor unit
 Inability to relax the quadriceps
 Instability or weakness of the knee joint
 Inability to contract the quadriceps