A tear or strain in the latissimus dorsi muscle, commonly called the “lat,” can be a significant injury. This muscle is the largest in the upper body, and an injury here causes symptoms that range from minor discomfort to a total inability to move the arm. Understanding the immediate sensations and ongoing signs of a lat tear is crucial for determining the severity and appropriate next steps for care.
The Latissimus Dorsi Muscle
The latissimus dorsi is a broad, triangular muscle spanning a significant portion of the back. It originates from a wide area, including the lower six thoracic vertebrae, the lumbar spine through the thoracolumbar fascia, and the posterior iliac crest, effectively connecting the back to the pelvis. The muscle fibers converge into a narrow tendon that inserts onto the front of the humerus. This extensive attachment pattern allows the lat muscle to perform several powerful actions on the shoulder joint.
The primary functions of the latissimus dorsi are the adduction, extension, and internal rotation of the arm. These movements are used in everyday activities like pulling a rope or performing a pull-up, where the muscle pulls the trunk upward when the hands are fixed overhead. Because of its role in powerful pulling and throwing motions, the lat is frequently strained during activities involving a sudden, forceful contraction or eccentric overload, such as in baseball pitching or competitive climbing.
Immediate Sensations of Injury
The moment a latissimus dorsi tear occurs is often marked by an acute sensation. Many individuals report hearing or feeling a distinct “pop,” “snap,” or “ripping” sound. This sign is frequently followed by an immediate, searing, sharp pain. The pain is typically felt deep in the side, often radiating from the armpit area, down the side of the torso, or toward the lower back.
The pain is usually accompanied by a sudden, profound weakness in the affected arm and shoulder. This weakness makes it difficult or impossible to continue the activity that caused the injury, as the muscle can no longer contract effectively. Following the initial event, the area may quickly develop involuntary muscle contractions or spasms. A feeling of burning pain may also be present, particularly near the site of the tear.
Identifying Severity Based on Symptoms
Latissimus dorsi injuries are classified into three grades based on the extent of muscle fiber damage. A Grade 1 injury, or mild strain, involves only a minor tear of the muscle fibers, causing localized tenderness and mild pain. The strength and range of motion are minimally affected, and the pain is primarily noticed during movements that specifically engage the muscle, like pulling or reaching.
A Grade 2 injury signifies a moderate or partial tear of the muscle fibers. The symptoms are more pronounced, including significant pain, a noticeable loss of strength, and restricted range of motion. Visible bruising and swelling may appear in the affected area several hours or days after the event, often tracking down the side of the torso. The person will likely find it difficult to perform routine movements, such as lifting the arm overhead or reaching behind the back.
The most severe injury, a Grade 3 tear, represents a complete rupture of the muscle or its tendon. This level of trauma results in excruciating pain and a near-total loss of function. A primary physical symptom is the presence of a palpable defect, which feels like a gap or divot in the muscle belly where the tissue has separated. In some cases, the muscle tissue may retract and form a visible lump or bulge below the shoulder blade or in the armpit area.
Next Steps and Seeking Professional Care
Following the acute injury, immediate self-care involves rest and cold application. Resting the arm and avoiding any activity that causes pain prevents further damage to the torn fibers. Applying a cold pack wrapped in a thin towel to the painful area for 15 to 20 minutes every few hours helps to reduce inflammation and manage the initial pain.
It is important to seek professional medical evaluation for any suspected lat tear, as self-diagnosis cannot accurately determine the grade of injury. Urgent care is necessary if the pain is severe, if there is a noticeable deformity or palpable gap in the muscle, or if the arm cannot be moved at all. A physician will perform a physical exam to assess pain and weakness, and they may use imaging tests like an MRI to confirm the tear’s location and severity.
Professional diagnosis is necessary for grading the tear and ruling out other potential issues, such as a rotator cuff injury or a rib fracture. Treatment for a lat tear is dependent on the grade, and a medical professional will guide the recovery. This typically involves a period of immobilization followed by a tailored physical therapy program. For the most severe Grade 3 ruptures, surgical repair may be required to restore strength and function.