AC joint Injury

AC joint Injury
The acromion consisted of the acromion (portion of the scapula) and the clavicle.  It is a diarthrodial articulation with a meniscal disk.  AC joint injuries usually occur in young athletic populations and occur with trauma/ fall with arm out stretched.  Sever ligament provide stability to the AC joint (coracoclavicular, cocracoacromial) and are sprained during the an AC joint injury.
AC joint are classified based upon lament and structural damage.
Type I
-Sprain of the acromioclvicular ligament, intact joint capsule, intact coracoclvcular ligament, intact deltoid and trapezius
Type II
-Rupture of AC ligament and joint capsule

Type III
-Rupture of AS and CC ligaments, elevated clavicle and detached deltoid/trap

Type IV
-AC/CC/joint capsule rupture, displaced clavicle into the trap

Type V
-Rupture of AC/CC/joint capsule, clavicle 100% displaced

Type VI
- Rupture of AC/CC/joint capsule, clavicle displacement behind biceps tendon
Type I and II are treated non-operatively as there are merely strains.  Greater then type III is treated through surgical intervention.  Debate on efficacy of non-operative and surgical intervention for some type III AC joint injuries.  Complications for non-operative type III dysfunctions is potential impingement syndrome.
AC joints have a pain arc from at EROM from 120-160 degrees unlike impingement and RTC pathologies that have a pain arc through mid-range.