AC Joint Injuries
The acromioclavicular joint (ACJ) is the joint sitting atop the shoulder between your deltoid and the base of the neck, and is where the top of the shoulder blade meets the clavicle bone.
Commonly in contact sports such as American football, rugby and combat sports such as wrestling, the top of the shoulder can forcefully strike an opponent and cause injury at this joint. As such, rather than running congruently with the top of the shoulder, deformations of the joint can occur when placed under strain as demonstrated clearly by Gilbert Melendez in his recent UFC on Fox 7 lightweight title fight against Benson Henderson (see picture above).
The ACJ is usually injured from a direct impact to the point of the shoulder or outer point of the collar bone. The amount of joint damage is classified commonly in terms of the amount of joint displacement (separation) which infers a specific degree of injury to the acromioclavicular joint ligaments.
Classification & Diagnosis
ACJ injuries are classified as follows:
I: An ACJ sprain only (Minimal- <50% collar bone elevation or subluxation)
II: ACJ ligament and joint capsule tear, 50% collar bone elevation or subluxation)
III: Disruption to ACJ ligament, capsule and coracoclavicular ligaments. 100% dislocation of the collarbone upwards and loss of contact between collar bone and shoulder blade.
* IV: Disruption to ACJ ligament, capsule and coracoclavicular ligaments. 100% dislocation backwards into or through the trapezius muscle.
* V: Disruption to ACJ ligament, capsule and coracoclavicular ligaments. Dislocation with 100-300% separation between collar bone and shoulder blade. Detachment from collarbone and deltoid & trapezius muscles.
* VI: Disruption to ACJ ligament, capsule and coracoclavicular ligaments. ACJ dislocated with collar bone moving beneath the acromion and coracoid process(downwards)
* NB: For grades IV- VI early surgical intervention is required.
Grade I-III injuries are usually managed conservatively with anti-inflammatory medications, analgesia and physiotherapy interventions.
In my experience there are a few type of presentations for these grade ACJ injuries which individuals will suffer from.
1. Pain only
Grade I injuries will commonly not demonstrate laxity or movement of the clavicle out of joint, but will report pain specifically on palpation of the joint, on loading of the arm above head height or at end of range elevation or reaching across the body. Usually this will settle within the correct healing times for ligaments (8-10 weeks) with relatively non-strenuous activity being undertaken. Pain can be managed by icing frequently to prevent swelling accumulating and disrupting joint mechanics, and by keeping active to gently increase the load bearing tolerance of the ligaments.
2. Hypomobile with no laxity
These patients may have initially a higher degree of ligament sprain, with laxity or collar bone movement, which has now become stiff but not out of place in the joint. These patients will have no obvious deformation, similar to those described above, but on pressure through the collar bone will have lost the small but important movement in this joint which is essential for good joint mechanics. They may require joint mobilisation to ensure the joints are able to function appropriately.
3. Hypomobile with laxity & deformation
This group of patients will demonstrate with a “step deformity” as Melendez does above which is always present, as their collar bone is being held “out of place”. Their ability to elevate their arm may be much more limited (to usually about 90°). These individuals will need mobilisation to a greater degree to improve joint motion, but then may require taping regularly to ensure the joint remains in place to allow the ligament to attempt to heal in position.
These patients will demonstrate a transient step deformity, with the movement of the collar bone changing dependent upon their activity. They will have less joint stiffness and pain is dependent upon the joint position (credit marvin). Taping is essential for these patients to ensure the joint stays in position.
General Rehabilitation Foci
Some specific components of rehabilitation should be undertaken to ensure a successful management of this injury.
• Classify properly and identify what is mechanically occurring at the ACJ
• Utilise closed chain exercises (where hands remain in contact with a stable surface), such as plank holds or push ups early to activate muscle stabilisers around the joint and the shoulder blade- whilst controlling movement of the ACJ.
• Start strengthening the arm below 90° before elevating higher, and ensure the joint remains in place.
• Tape, re-tape, teach your patient how to tape, get them to re-tape (if you feel the collar bone is elevating)
• Train the trapezius through exercises which retract (or bring backwards) the scapula, as this is an essential muscle to control the shoulder blade (e.g. Y’s or T’s/ Blackburn exercises)
• Do not over stress ACJ ligament tissue whilst it is healing
• Avoid prolonged immobilisation
• Muscle balance around the shoulder blade is essential (think 3 pulling exercises for every 1 pushing)
• Spend time of shoulder blade muscle strength (especially the trapezius)
• Improve posterior shoulder flexibility
• Consider proprioception and neuromuscular control
Stay Healthy and Keep Fighting!