Patients who report that their knee feels like it's going to give way may have an ACL deficiency. ACL stands for anterior cruciate ligament. It's one of two ligaments that criss-cross inside the knee and hold it together while it moves.
The giving way instability occurs mosts often during side-stepping movements or when the player has the foot planted on the ground and tries to rotate the leg around it.
There is a test called the pivot-shift test that may help pinpoint the problem. This test is used by orthopedic surgeons, physical therapists, and athletic trainers. It is the most reliable sign of this type of functional instability of the knee.
Sometimes a mild deficiency of the ACL can be rehabilitated. It takes a concentrated effort for about eight to 12 weeks at least. If there is still too much laxity or looseness and instability after rehab, then surgery to repair the ACL may be needed.