The clavicle, commonly called the collarbone, is a long, slender bone connecting the shoulder blade (scapula) to the breastbone (sternum). It acts as a strut, keeping the shoulder in place and allowing for a wide range of arm motion. Swelling in the area of the clavicle is a significant physical symptom because the bone is located just beneath the skin. Investigating the cause is important, as it can signal a simple strain or something requiring immediate medical attention.
Swelling Caused by Acute Injury
The most immediate and painful cause of clavicle swelling is a fracture, or a broken collarbone, accounting for approximately 5% of all adult fractures. This injury usually results from a direct blow to the shoulder or a fall onto an outstretched arm. Swelling appears rapidly as blood and fluid accumulate around the broken bone fragments and damaged soft tissues. The pain is severe, often accompanied by crepitus (a crunching sensation), and an inability to lift the arm.
Another common traumatic cause is a separation of the acromioclavicular (AC) joint, where the clavicle meets the shoulder blade. This injury disrupts the connecting ligaments, causing the outer end of the clavicle to push upward. The resulting swelling and visible bump are pronounced at the end of the collarbone.
Swelling can also occur at the sternoclavicular (SC) joint near the center of the chest. SC joint injuries are less common but result from high-impact trauma, such as car accidents. Damage causes localized swelling and tenderness near the breastbone. While most SC injuries are sprains, a posterior dislocation, where the clavicle moves backward, is a serious concern due to the proximity of major blood vessels and the trachea.
Swelling Related to Inflammation or Infection
Swelling that develops gradually, without a specific injury, often points to an underlying inflammatory process. Osteoarthritis can affect the AC or SC joints, causing intermittent swelling, stiffness, and pain. Systemic inflammatory conditions like Rheumatoid Arthritis can also target these joints, leading to persistent and symmetrical joint swelling.
A distinct cause of chronic swelling near the breastbone is Sternoclavicular Hyperostosis (SCH). This non-infectious condition involves the abnormal, excessive growth of bone around the SC joint. SCH causes a firm, non-tender enlargement of the medial clavicle and adjacent sternum. It is part of a spectrum of inflammatory disorders known as SAPHO syndrome, which involves synovitis, acne, pustulosis, hyperostosis, and osteitis.
When swelling is accompanied by intense warmth, redness, and a fever, an active infection should be considered. Cellulitis is a bacterial infection of the skin and underlying soft tissues that rapidly causes diffuse, painful swelling over the clavicle. If the infection penetrates the bone, osteomyelitis develops, causing deep, persistent pain and bone inflammation. Infections require prompt identification and treatment to prevent widespread tissue damage and possible sepsis.
Swelling Due to Masses and Growths
Swelling that presents as a distinct, palpable lump is considered a mass or growth, which can be either benign or malignant. Benign soft tissue masses include lipomas, which are fatty tumors that feel soft and movable under the skin. A ganglion cyst, a fluid-filled sac arising from a joint or tendon sheath, can also cause localized, firm swelling. These masses are typically painless and require investigation only if they cause discomfort.
Growths arising directly from the clavicle bone present as a harder, non-mobile swelling. Aneurysmal bone cysts are non-cancerous, blood-filled lesions that cause the bone to expand visibly. Primary malignant bone tumors of the clavicle are extremely rare but are characterized by a progressively enlarging, firm, and often painful mass. Imaging tests are necessary to differentiate these conditions from benign lesions.
In adults, a swollen clavicle can be the site of a metastatic lesion, meaning cancer has spread from a primary location elsewhere. Cancers originating in the lung, breast, or kidney can metastasize to the bone, causing localized swelling and structural weakness. This type of swelling warrants immediate investigation, even if it is the first sign of an underlying malignancy.
Swelling in the supraclavicular area, just above the collarbone, is frequently caused by enlarged lymph nodes (lymphadenopathy). While they often swell in response to a localized infection, a firm, non-tender supraclavicular lymph node can be a concerning sign of malignancy elsewhere and requires prompt medical workup.
Determining When to Seek Professional Care
While many causes of clavicle swelling are minor, certain associated symptoms indicate the need for immediate medical evaluation. Any swelling accompanied by severe, acute pain or the inability to move the shoulder or arm requires urgent attention, especially following an injury. Difficulty breathing or swallowing, which occurs with certain SC joint dislocations, is a medical emergency demanding immediate intervention.
Swelling accompanied by systemic signs, such as unexplained fever, chills, or night sweats, suggests a serious infectious process that must be rapidly addressed. Furthermore, any swelling that rapidly increases in size, is persistently painful, or is found alongside unexplained weight loss should be evaluated promptly. These findings guide a physician toward necessary diagnostic studies and potential biopsies.
A medical professional begins the diagnostic process with imaging, such as an X-ray, to evaluate the bone structure and look for fractures or bony growths. Depending on the initial findings, a computed tomography (CT) scan or magnetic resonance imaging (MRI) visualizes soft tissues, internal joint structures, and the extent of the mass. Blood tests are also ordered to check for markers of infection or systemic inflammation, helping to narrow the range of possible diagnoses.