Natural History of the Torn Anterior Cruciate Ligament
If left untreated the laxity which is immediately present only becomes worse. The other structures of the knee try in vain to provide some stability to the knee. Over time and with more usage these other structures stretch out as well, resulting in increased instability and then associated meniscal (cartilage) tears. There is an incidence of approximately 1 in 3 patients who at the time of the anterior cruciate ligament tear will tear their cartilage as well. This progresses with time because in an untreated knee the knee is unstable and produces greater stress on the cartilage. Up to 80% of the knees will eventually develop a cartilage tear. The smooth Teflon lining of the knee which is known as articular cartilage is often damaged at the time of the ACL tear. If left untreated, this will again progressively wear at the knee, causing an increased rate of osteoarthritis development. The patients will alter their gait and will develop a rather specific quadriceps avoidance gait because when they contract their quads during normal walking its slides the tibia forward which is usually stopped by the anterior crucial ligament. The patient will naturally and unconsciously try to prevent this. All these problems mean that the knee will progress to late degenerative changes and osteoarthritis much earlier than in a normal knee. There is not good evidence that bracewear alone will decrease the rate of re-injury to the knee. However, in older and non-active patients there is definitely a role for non-operative treatment by simply modifying their activities and avoiding all situations where they may pivot and damage their knee further.