The natural history and tailored treatment of ACL injury

The fate of the injured anterior cruciate ligament (ACL) is variable. The s pectrum of injury ranges from partial sprain (grade 1 or 2) to a complete d isruption (grade 3), which may occur in isolation or in combination with in jury to other structures in the knee. Postinjury symptoms of knee instabili ty usually depend on the degree of joint laxity and the athletic demands of the individual. If an ACL injury is left untreated, repeated episodes of s ubluxation can inflict further intraarticular damage, with an increased ris k of developing osteoarthritis. Predicting the outcome after ACL injury is difficult, and treatment should be individualized.