Seventy percent of ACL injuries occur through non-contact mechanisms such as pivoting, sidestepping maneuvers or awkward landings where the individual is not in control. The other 30% of ACL injuries occur from direct impact, such as a forceful tackle on the outer side of the knee.
Patients with an ACL injury usually experience a “pop” in the knee at the time of injury followed by pain and swelling around the knee over the next 24-48 hours. Some individuals who suffer an ACL tear feel that their knee is unstable and are unable to support their body weight. The knee then becomes stiff and sore for 2-3 weeks during which time it is helpful to participate in physical therapy to regain motion, strength and daily function