The serratus anterior is a fan-shaped muscle located along the outer side of the rib cage, just beneath the armpit. Because the discomfort can feel like rib or chest pain, it often causes confusion when it becomes painful. It wraps around the back of the scapula (shoulder blade) and attaches to the ribs. Its location makes it susceptible to strain from common movements, making addressing the underlying cause key to finding relief.
Anatomy and Function of the Serratus Anterior
The serratus anterior is a broad muscle originating from the outer surfaces of the upper eight or nine ribs, giving it a saw-toothed appearance. It inserts along the entire length of the medial border of the scapula, which is responsible for its powerful stabilizing function during arm movement.
The muscle’s primary action is scapular protraction, pulling the shoulder blade forward and around the chest wall, earning it the nickname “the boxer’s muscle.” It also works with the trapezius muscle to upwardly rotate the scapula, which is necessary for elevating the arm overhead.
The serratus anterior plays a significant role in anchoring the shoulder blade against the rib cage to maintain shoulder joint stability. If the muscle is weak or dysfunctional, the shoulder blade can lift away from the rib cage, a condition known as “scapular winging.” The long thoracic nerve provides the electrical signals that allow this muscle to contract.
Common Musculoskeletal Causes of Pain
The most frequent cause of serratus anterior pain is muscle strain or overuse, often resulting from repetitive activities involving pushing, throwing, or lifting. Sports like swimming, tennis, boxing, and weightlifting can overload the muscle, especially if intensity or volume increases suddenly. This overuse leads to micro-tears in the muscle fibers, causing localized tenderness and pain.
Poor posture, particularly a chronic slouch, places the serratus anterior in a mechanically disadvantaged position. When the shoulder blades are habitually protracted, the muscle must work harder to maintain stability, leading to chronic tension and myofascial trigger points. These trigger points manifest as persistent, deep aching pain around the side of the rib cage.
Scapular winging, where the serratus anterior fails to anchor the shoulder blade, is a significant source of chronic pain. This failure is often linked to muscle weakness or injury to the long thoracic nerve. When the muscle cannot stabilize the scapula, other muscles must overcompensate, causing widespread shoulder and upper back pain.
Direct trauma, such as a fall or impact to the side of the chest, can cause acute pain by bruising or straining the muscle against the ribs. Even prolonged, intense coughing can strain the serratus anterior, as the muscle assists in expanding the rib cage.
Initial Self-Care and Home Management
For mild pain presumed to be a muscle strain, initial self-care focuses on reducing inflammation and allowing the muscle to rest. Activity modification is the first step, involving the temporary cessation of activities that aggravate the pain, such as heavy lifting or repetitive overhead movements.
Applying ice to the painful area for 15 to 20 minutes several times a day during the first 48 hours helps manage acute pain and swelling. After this initial phase, alternating between heat and ice can promote blood flow and relax the muscle tissue.
Gentle, sustained stretching helps restore the muscle’s resting length and alleviate tension. Simple stretches like reaching the arms overhead or performing a side bend can target the serratus anterior, but these should be performed slowly and stopped if they increase the pain. Over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, may be used for short-term pain relief, but consultation with a healthcare provider is recommended.
Self-massage techniques, using fingertips or a small ball, can be applied to the area to help release taut bands or trigger points. Focus on gentle pressure along the side of the rib cage, just under the armpit, avoiding forceful pressing. These home strategies are intended for temporary management of mild muscle soreness.
Indicators for Professional Medical Consultation
While most serratus anterior pain is musculoskeletal and resolves with rest, certain symptoms warrant consultation with a medical professional. If the pain is severe, constant, or progressively worsens despite a week of home care, professional evaluation is required.
Signs that the pain may stem from a more serious underlying issue include difficulty breathing, severe chest pain, or coughing up blood. Pain in this area can sometimes mimic or overlap with cardiac or pulmonary issues, and systemic symptoms like fever, unexplained weight loss, or night sweats necessitate urgent medical attention.
Noticeable scapular winging that develops suddenly or is accompanied by weakness in the arm suggests a possible injury to the long thoracic nerve, requiring neurological assessment. Pain that radiates into the arm or is accompanied by numbness or tingling should also be investigated to rule out nerve compression or referred pain from the spine.
Pain in this region can also be referred from the neck or thoracic spine, or related to conditions like intercostal neuralgia or a rib stress fracture, especially in athletes. A doctor can perform a thorough examination, which may include imaging or specialized testing, to accurately diagnose the source of the pain and recommend appropriate treatment.