A collarbone can be dislocated, though the injury rarely involves the long bone segment itself. The clavicle, commonly known as the collarbone, is a long, horizontal bone that acts as a strut connecting the trunk to the shoulder. Instead of fracturing through the middle, the bone’s ends are susceptible to displacement from the joints they form. When people speak of a “dislocated collarbone,” they are almost always referring to the separation or instability of one of the two joints at either end of the bone.
The Anatomy of Collarbone Instability
The stability of the shoulder complex depends on two joints where the clavicle articulates with other bones.
Acromioclavicular (AC) Joint
At the outer, lateral end, the clavicle meets the acromion to form the Acromioclavicular (AC) joint. This joint is primarily stabilized by the AC ligaments and the stronger coracoclavicular ligaments that anchor the clavicle to the underlying coracoid process of the scapula. When these ligaments are stretched or torn, the injury is described as an AC joint separation, with the severity graded based on the degree of ligament damage and displacement.
Sternoclavicular (SC) Joint
At the inner, medial end of the clavicle, the bone connects to the sternum, or breastbone, forming the Sternoclavicular (SC) joint. The SC joint is the only direct connection between the arm and the main skeleton. This joint gains its stability from strong anterior and posterior sternoclavicular ligaments, as well as the costoclavicular ligament, which connects the clavicle to the first rib. Dislocation at the SC joint is far less common than an AC separation but can carry unique risks due to its proximity to important structures in the chest.
Recognizing a Clavicle Joint Dislocation
The immediate signs of a clavicle joint dislocation center on localized pain and noticeable physical changes. Sharp, intense pain occurs directly over the affected joint, exacerbated by any attempt to move the arm or shoulder. Swelling and bruising are common at the injury site as the soft tissues and ligaments surrounding the joint sustain damage.
A visible deformity, often described as a bump or prominence, is a defining symptom, particularly with higher-grade AC separations where the clavicle pushes upward beneath the skin. In the case of an SC joint injury, the end of the collarbone may protrude forward (anterior dislocation) or, less commonly and more dangerously, backward (posterior dislocation). Patients frequently report a limited range of motion and may instinctively support the injured arm to prevent movement.
Common Causes and Mechanisms of Injury
AC Joint Mechanisms
Acromioclavicular joint separations most frequently occur from a direct fall onto the point or tip of the shoulder, driving the shoulder blade downward while the clavicle remains in place. This mechanism is common in sports that involve a high risk of falling, such as cycling, skiing, and contact sports. The force of the impact tears the ligaments, allowing the clavicle and acromion to separate.
SC Joint Mechanisms
Sternoclavicular joint dislocations generally require a more substantial and focused force due to the joint’s robust ligamentous support. These injuries often happen during motor vehicle accidents, typically from a blow to the front of the chest or shoulder. A force applied to the lateral shoulder that rotates the shoulder backward can cause an anterior SC dislocation, which is the more common direction. A force that pushes the shoulder forward can result in a posterior dislocation, which is a less frequent but potentially serious injury.
Treatment and Recovery Pathways
Management for a suspected clavicle joint dislocation involves immediate immobilization of the arm, typically with a sling, and the application of ice to reduce swelling and pain.
Non-Surgical Treatment
Low-grade AC separations, which involve only sprains to the ligaments, are managed non-surgically with rest, anti-inflammatory medication, and a short period of sling support. Physical therapy is then introduced to restore full range of motion and strength, with recovery often taking several weeks to a few months.
Surgical Treatment
More severe AC separations (Grades 3 and higher) and most symptomatic SC joint dislocations may require surgical intervention to restore joint alignment and stability. For AC injuries, surgery aims to reconstruct the torn coracoclavicular ligaments and fix the bones in their correct anatomical position. SC joint surgery is often necessary for posterior dislocations because the backward displacement can compress vital structures like the trachea or major blood vessels, requiring urgent reduction and stabilization. Recovery following surgery involves extensive physical rehabilitation, typically taking three to six months before a full return to high-demand activities.