The clavicle, commonly known as the collarbone, is a slender, S-shaped bone connecting the sternum (breastbone) to the scapula (shoulder blade). This bone acts as a strut, transferring force from the arm to the rest of the skeleton. Because of its exposed position and role in shoulder movement, pain in the left collarbone is a frequent complaint. The discomfort can stem from a simple local irritation or signal a serious condition affecting an internal organ. Understanding the potential causes, from acute mechanical injury to referred pain, is the first step toward appropriate care.
Localized Injuries and Mechanical Stress
The most straightforward causes of left collarbone pain involve acute trauma or repetitive mechanical stress affecting the bone or surrounding joints. A clavicle fracture, or broken collarbone, is a common injury often resulting from a fall onto the shoulder or an outstretched arm. This injury typically presents with intense, sudden pain, swelling, and a visible bump or deformity. Shoulder movement usually produces a grinding or crackling sensation known as crepitus.
Another frequent traumatic injury is an acromioclavicular (AC) joint separation, often called a shoulder separation. This occurs where the clavicle meets the shoulder blade. Ligaments connecting these bones can tear due to a direct blow, causing pain at the top of the shoulder and sometimes a noticeable protrusion or bump. The severity is graded based on the extent of ligament damage and resulting joint displacement.
Overuse injuries and muscle strains are common sources of pain near the collarbone. Repetitive activities, such as certain weightlifting movements, can lead to distal clavicular osteolysis, sometimes called “weightlifter’s shoulder.” This involves the breakdown of bone at the AC joint. Strains in surrounding muscles, like the pectoralis or trapezius, can also refer pain and tenderness to the collarbone area, particularly after strenuous exercise or poor posture.
Degenerative Conditions and Nerve Compression
Pain that develops gradually may indicate a chronic or degenerative condition affecting the joints or nervous system near the collarbone. Arthritis is a common culprit, often affecting the sternoclavicular (SC) joint (where the clavicle meets the breastbone) or the AC joint. Osteoarthritis, or “wear and tear” arthritis, causes the protective cartilage to thin, leading to pain, stiffness, and sometimes a grinding sound with movement.
Inflammatory conditions, such as rheumatoid arthritis, can also target the SC joint, resulting in swelling, redness, and pain that may radiate into the neck and chest. These changes cause a gradual narrowing of the joint space and the formation of bony spurs. Unlike acute injuries, this pain is chronic and worsens over time, sometimes accompanied by morning stiffness.
Chronic pain can also involve nerve or vascular compression, most notably Thoracic Outlet Syndrome (TOS). The thoracic outlet is the narrow space between the collarbone and the first rib, through which major nerves (the brachial plexus) and blood vessels pass into the arm. Compression here can cause vague, aching pain in the shoulder and neck, often accompanied by numbness, tingling, or weakness extending down the arm and into the fourth and fifth fingers. This compression can be mechanical (such as from an extra rib) or due to poor posture or overly tight muscles.
Referred Pain from Internal Organs
The left collarbone is an area where pain originating from internal organs may be felt, a phenomenon known as referred pain. This occurs because the nerves supplying internal structures share pathways with the nerves of the shoulder and collarbone region. The most concerning source of referred pain to the left clavicle area is a cardiac event, such as angina or a heart attack.
In a heart attack, the pain often begins in the chest but can radiate outward to the left arm, jaw, neck, or shoulder area. This discomfort is described as pressure, squeezing, or fullness, and is often accompanied by symptoms like shortness of breath, cold sweats, or nausea. The pain does not usually worsen with movement or deep breaths, which helps distinguish it from musculoskeletal pain.
Referred pain can also originate from the abdominal cavity, specifically the spleen, which is located on the left side. A ruptured or injured spleen can cause a severe form of referred pain known as Kehr’s sign. This occurs when irritation of the diaphragm by blood is transmitted through the phrenic nerve. Since the phrenic nerve shares nerve roots with the supraclavicular nerves, the patient feels acute pain at the tip of the left shoulder or above the collarbone.
Less commonly, pulmonary issues can manifest as pain near the collarbone, such as with a Pancoast tumor. This rare type of lung cancer develops at the apex of the lung. As the tumor grows, it can press on the nearby brachial plexus nerves or invade surrounding bony structures, including the upper ribs and clavicle. The resulting pain is severe, persistent, and may radiate down the arm, often preceding classic respiratory symptoms.
Warning Signs Requiring Immediate Care
While many causes of collarbone pain are musculoskeletal, certain accompanying symptoms signal a medical emergency. Any sudden, crushing chest pain or discomfort that radiates to the left collarbone, arm, or jaw must be treated as a potential heart attack. This risk is heightened if the pain is accompanied by shortness of breath, lightheadedness, or profuse sweating.
Following any trauma, seek emergency care if the collarbone appears visibly deformed, if there is an inability to move the arm, or if the skin over the bone is broken. Symptoms of nerve or blood vessel compromise indicate a potentially serious vascular or neurological injury. These include severe numbness, tingling, weakness, or the arm/hand becoming cold or blue. Additionally, pain accompanied by a high fever, chills, or redness and warmth over the joint may suggest a joint or bone infection (osteomyelitis), which requires urgent medical intervention.