A ligament is a structure that links two bones together. Sprains often happen when a ligament is 'stretched' beyond its capability. Common ligaments that are sprained include the ATF- anterior talofibular (ankle), Deltoid (ankle), MCL- medial collateral ligament (knee), ACL- anterior cruciate ligament (knee), AC- acromioclavicular (shoulder), UCL- ulnar collateral ligament (elbow). A severe sprain is considered a rupture (i.e. a Grade 3 ACL Sprain is the same as a torn ACL). In skeletally immaturely individuals, growth plate and avulsion fracture injuries are often confused for tendon, ligament, or muscle injuries, so it is important to get them evaluated by an athletic trainer or other professional.