INTRODUCTION
ANATOMY
The serratus anterior is a fan-shaped muscle found at the lateral wall of the thoracic cavity. Because of its anatomical course, it has a “saw-toothed,” i.e., “serrated” appearance, also known as the “boxer’s muscle. ”
The main functions of the serratus anterior are front and lateral movements and rotation of the scapula.
CAUSES OF PAIN
The serratus anterior muscle can become painful. The pain most often occurs due to overuse, tension, or stress. The serratus anterior pain is most common in sports with repetitive shoulder motions, for example, in swimming, tennis, and weightlifting (especially heavy lifting).
Furthermore, peripheral neuropathies and motor neuron diseases can lead to muscle weakening and, consequently, pain. Trigger points are also a possible cause of the serratus anterior muscle pain.
Another but rare cause of serratus anterior pain is serratus anterior myofascial pain syndrome – a myofascial pain syndrome.
However, the pain in the serratus anterior usually occurs after muscle injuries or due to certain medical conditions, including rib fractures, asthma, inflammation or infection of the lung tissues, and ankylosing spondylitis.
In most cases of serratus anterior pain, the pain originates from the muscle itself. The trigger points in the muscle are the spots of increased sensitivity and irritability, presenting with different pain patterns. These spots represent the muscle knots that can cause localized or referred pain in other, usually adjacent, areas of the body.
Serratus anterior trigger points can become activated by other stressors to the muscle, causing pain. These trigger points are pretty common in patients suffering from shoulder joint dysfunction. Interestingly, even fast running or sprinting can overload the serratus anterior muscle and activate its trigger points.
Swinging the arms during running can be pretty intense, and because the serratus anterior is responsible for the forward swing, this movement can lead to muscle overload and trigger point activation.
Consequently, this causes pain. Furthermore, lung problems and a severe cough can activate the trigger points because it often requires deep breathing, which overloads the serratus anterior. Postural stress, i.e., bad posture, is also one of the causes of serratus anterior trigger point activation.
SYMPTOMS
If one is experiencing pain in the chest, arm, or back, along with a decreased range of motion in the shoulder joint, serratus anterior muscle pathology should be suspected. The symptoms of the serratus anterior pain can also include difficulty in lifting the arm overhead, reduced range of motion with the arm, as well as arm or finger pain, sensitivity, tightness, shoulder blade pain, pain in the chest, and difficulty with deep breathing.
Painful serratus anterior can cause referred pain to other regions of the body. It is, therefore, sometimes pretty difficult to diagnose the serratus anterior pathology or find the trigger points.
If the causes of the serratus anterior muscle pain are trigger points, one could experience pain at the lateral part of the ribcage and at the inner and lower parts of the shoulder blade. Moreover, the serratus anterior pain originating from trigger points can be referred to other areas, mainly radiating down the inner arm, including the 4th and 5th finger. Furthermore, serratus anterior trigger points could mimic the symptoms of a heart attack. It is, therefore, highly important to be aware of the trigger points, which are sometimes underlooked and neglected causes of muscle pain.
Usually, serratus anterior pain is not a result of a severe medical condition. However, immediate medical care is required in case the pain is accompanied by the following symptoms:
- Dizziness,
- Difficulty breathing,
- Stiff neck,
- High fever,
- Bull’s eye rash, or a tick bite,
- The onset of pain with the introduction of a new medication or increasing dosage of existing therapy,
- Worsening of the chest/back pain, or pain that does not improve with rest,
- The pain interferes with sleep and daily activities.
DIFFERENTIAL DIAGNOSIS
There are many differential diagnoses of serratus anterior trigger point pain, such as chronic neck pain, instability of the glenohumeral joint, slipped or broken rib, and shoulder impingement syndrome.
TREATMENT
The treatment of serratus anterior muscle pain depends on the cause. In order to effectively treat serratus anterior muscle pain, one has to know the exact cause. Throughout medical history and physical examination are the first steps in the diagnostic process and, eventually, successful treatment.
The treatment ranges from the RICE protocol (Rest, Ice, Compression, Elevation) over the nonsteroidal anti-inflammatory drugs (NSAIDs), oral steroids and muscle relaxants to warm compresses, dry needling, massages and injections.
The trigger point release is usually effective in pain release. After the trigger points in the serratus anterior are released, the muscle, which was previously feeling tight, may feel looser, having a larger pain-free range of motion. Furthermore, the muscle should be able to contract and relax better than earlier, following the trigger point release. In rare cases, patients with painful serratus anterior muscle may require surgery.
MD, PhD. Physical Medicine & Rehabilitation Physician from São Paulo - Brazil. Pain Fellowship in University of São Paulo.