ACL injuryBy Mayo Clinic staff
Original Article: http://www.mayoclinic.com/health/medical/IM04521
The anterior cruciate ligament (ACL) is one of the key ligaments that helps stabilize your knee joint. The ACL connects your thighbone (femur) to your shinbone (tibia). It's most commonly torn during sports that involve sudden stops and changes in direction — such as basketball, soccer, tennis and volleyball.