Injury to the knee during sports participation often involves partial or full detachment of the anterior cruciate ligament (abbreviated as ACL). ACL tears cause pain, swelling and inflammation. While the swelling and inflammation usually goes away in time, individuals with ACL injuries may experience pain and notice knee instability (knee slipping, etc.). Often surgery can repair or replace the ACL within the joint, allowing individuals the ability to walk or run again pain free or participate in sports. Unfortunately, osteoarthritis of the knee, which also causes pain and swelling, can occur in that same knee 10-20 years later for reasons which are not well understood.