Pain where the collarbone meets the breastbone, known as the sternoclavicular (SC) joint, is a common complaint. This discomfort can range from a mild ache to sharp pain that limits arm movement. Although the SC joint is robust and injuries are relatively uncommon compared to other shoulder structures, understanding the underlying causes is essential for effective management.
Understanding the Sternoclavicular Joint
The sternoclavicular joint is a small but functionally significant structure located at the base of the neck. It forms the only true skeletal connection between the upper limb and the axial skeleton. Specifically, it is the articulation between the medial end of the clavicle and the manubrium.
Despite its small size, this joint is classified as a synovial saddle joint, allowing for movement in multiple directions, including elevation, depression, and rotation. This wide range of motion allows the arm to move through its full arc. The joint is stabilized by a strong joint capsule, multiple reinforcing ligaments, and an intra-articular fibrocartilage disc that acts as a shock absorber.
The strength of the ligaments surrounding the SC joint is substantial, meaning it requires a significant amount of force to cause an injury. However, the joint’s functional role in transferring force from the arm to the body also makes it susceptible to stress. Issues here can profoundly affect overall shoulder function due to the combination of high mobility and structural dependence.
Traumatic and Inflammatory Causes of SC Joint Pain
Pain in the SC joint is broadly categorized into conditions resulting from sudden trauma or those stemming from progressive inflammatory and degenerative processes. Traumatic injuries most often involve a direct impact to the joint or a forceful blow to the shoulder, such as from a sports collision or a motor vehicle accident.
Traumatic Injuries
The mildest traumatic event is an SC joint sprain, which involves a stretching or partial tearing of the stabilizing ligaments. More severe trauma can lead to a complete dislocation, where the end of the clavicle separates entirely from the sternum. Dislocations are classified based on the direction the clavicle moves.
An anterior dislocation, where the clavicle end moves forward, is the most common form of instability at this joint. While painful and causing an obvious bump, anterior dislocations are not considered medically urgent. Conversely, a posterior dislocation, where the clavicle moves backward behind the sternum, is a rare but serious injury.
This posterior displacement is concerning because several vital structures lie immediately behind the joint, including the trachea, esophagus, and major blood vessels. Compression or damage to these structures can lead to difficulty breathing or swallowing, requiring immediate medical attention and urgent reduction of the joint.
Inflammatory and Degenerative Conditions
The most frequent non-traumatic cause of SC joint pain is osteoarthritis, a degenerative condition related to wear and tear over time. This condition affects individuals over 50, though it can occur earlier, and results from the gradual breakdown of the smooth articular cartilage covering the bone ends. As the protective cartilage wears away, bone may rub against bone, causing pain, stiffness, and sometimes a grinding sensation with movement.
Less commonly, the joint can be affected by other inflammatory conditions, such as rheumatoid arthritis, an autoimmune disorder. This systemic condition can cause inflammation, bony erosion, and joint damage in the SC joint, similar to other joints. Another rare possibility is infectious arthritis, where a bacterial infection settles in the joint, causing severe localized pain, swelling, warmth, and often a fever.
Pain can be referred to the SC joint area from a nearby condition like costochondritis or Tietze syndrome, which involves inflammation of the cartilage where the ribs meet the sternum. While these conditions can mimic SC joint pain, a detailed physical examination helps differentiate them from true SC joint pathology.
Diagnostic Evaluation and Red Flags
A healthcare provider’s evaluation of SC joint pain begins with a thorough clinical assessment, including a detailed medical history and a physical examination. The examination involves palpating the joint for localized tenderness, swelling, or deformity, and testing the arm and shoulder’s range of motion to see which movements reproduce the pain.
To confirm a diagnosis, imaging studies are often necessary. Standard X-rays are the first step, helping to rule out fractures and providing evidence of degenerative changes associated with osteoarthritis. However, due to the joint’s location, X-rays may not always clearly visualize subtle instability or dislocation.
A Computed Tomography (CT) scan is often considered the best imaging modality for the SC joint, particularly when a dislocation is suspected. A CT scan provides detailed cross-sectional images that clearly show the bony alignment and the degree of displacement. Magnetic Resonance Imaging (MRI) is used to evaluate soft tissue structures, such as ligaments, the joint capsule, and the intra-articular disc, which is useful when assessing sprains or chronic instability.
The presence of certain symptoms, known as red flags, demands immediate medical attention. These include severe, unrelenting pain, a rapidly worsening deformity, and especially any difficulty with breathing or swallowing. These signs can indicate a rare but dangerous posterior dislocation, where the displaced clavicle may be compressing the trachea or major blood vessels behind the sternum.
Treatment Modalities for SC Joint Issues
Treatment for sternoclavicular joint issues is highly dependent on the underlying cause and severity, often beginning with conservative, non-surgical approaches. For mild sprains or early-stage osteoarthritis, initial management involves rest and activity modification to avoid painful movements.
Non-Steroidal Anti-Inflammatory Drugs (NSAIDs), such as ibuprofen, are commonly used to reduce pain and inflammation in the joint. Temporary immobilization with a sling or a specialized brace may be recommended for acute sprains or stable anterior dislocations to allow the ligaments to heal.
If pain persists, interventional treatments become an option. Physical therapy is often prescribed to strengthen the surrounding muscles and improve shoulder stability and function. For chronic inflammatory pain, particularly from osteoarthritis or other inflammatory arthropathies, a corticosteroid injection directly into the joint can provide significant, though temporary, relief from swelling and discomfort.
Surgical intervention is reserved for cases that do not respond to conservative management or for severe injuries. Acute posterior dislocations are treated as a medical emergency and require a prompt closed reduction, which involves maneuvering the joint back into place, often under anesthesia. If a joint is severely unstable due to chronic dislocation or advanced arthritis, surgical procedures like open reduction and stabilization, or joint resection and fusion, may be considered to restore function and alleviate pain.