How will the knee function if the ACL is torn?
If no structure other than the ACL is injured, the knee usually regains it range of motion and is painless after six or eight weeks. The knee can then feel completely normal. However, it can be a “trick knee”. If a knee does not have an ACL it can give way or be unstable when the person pivots or changes direction. The person can usually run straight ahead and ride a bicycle without a difficulty. However, when the person with a torn ACL makes a quick turning motion away from the planted foot, the knee tends to give way and collapse. This abnormal motion can damage the menisci or articular cartilage and cause further knee problems.
