Tearing the ACL
A torn ACL is often accompanied by a muted, but still quite loud, popping sound. Immediately after tearing the ACL, it is common to feel intense pain. Sometimes, however, people who tear their ACL experience more of a strong uncomfortable tugging, similar to a strain. Even the strongest of individuals may collapse to the ground clutching their knee. Although the worst of the pain or discomfort may subside rather quickly, the swelling that typically follows can sometimes be extreme to the point that walking is difficult.
Once the ACL is torn, the knee may feel like it has too much “play.” The tibia, lacking the necessary support, can suddenly shift too far forward. This may cause the knee to buckle and create the sensation that the knee is giving way. In addition to making the knee mechanically less stable, a torn ACL makes it more difficult to sense the position of the knee as it moves. This can produce feelings of unsteadiness and impair one’s sense of balance. For some people, however, difficulty in fully bending or flexing the knee may be the dominant sensation.
A torn ACL can be compared to a rope that is stressed beyond its tolerance. With a complete tear, it snaps, causing the band of fibers to unravel. Even when the ACL undergoes a partial tear rather than a complete one, the ligament is still compromised.