The Anatomy of the Pectoralis Minor Muscle

The pectoralis minor muscle is a small, flat, triangular-shaped muscle located in your chest. The muscle, also know known as pec minor, is located beneath its counterpart pectoralis major and serves to move both your ribs and shoulder blade. Injury to your pec minor may cause difficulty with shoulder motions and proper rib elevation, and the muscle may be implicated in postural impairments.

The pectoralis minor originates as small flat strips from the surface of ribs three, four, and five. (Some people have strips coming from rib number two, and some from rib number six.) From its origin at the ribs, the pec minor travels up and inserts at the coracoid process of the shoulder blade. This small bone protrudes forward from the top of your shoulder blade, over your ribs, and towards your chest. You have two pectoralis minor muscles, one on each side of your body.

The pectoralis minor forms the anterior (front) wall of your axilla, or armpit.

There are several important structures that course through or near your pectoralis minor. The brachial plexus, a bundle of nerves that comes from your neck and travels to your arm, courses just under your pec minor. Your subclavian artery and vein also course underneath your pec minor. These vascular structures move blood to and from your arms. Pinching of these nerve and vascular structures between your pectoralis minor and ribs may cause pain, numbness, or tingling in your arm.

The pectoralis minor is innervated by the medial pectoral nerves that arise from cervical level eight and thoracic level one of your spine. Blood is supplied to the pec minors via the thoracoacromial artery.

There are several functions of the pectoralis minor muscle depending on the position of your body. When your ribs are stabilized, the pec minor helps to draw your shoulder blades forward and internally. They also serve to depress your shoulder blades, pulling them down. When your shoulder is stabilized, the pec minor elevates your ribs. Therefore, the pectoral muscles can be considered an accessory muscle of inspiration; as you breathe in, the pec minor contracts to draw your ribs up, allowing air to fill your lungs.

The pectoralis minor also works with your serratus anterior to bring your shoulder blades forward. This muscle force-couple allows for full range of motion of the shoulder blades and shoulder complex.

Isolated injury to the pectoralis minor is rare, and only a few cases have been described in the scientific literature. There are several conditions, though, where the pec minor may be implicated. These may include:

• Postural syndrome. A forward head, rounded shoulders posture may place your pec minor in a shortened position. This can draw your shoulders forward, causing pain and limited mobility in your upper extremities. Poor posture with a shortened pec minor may lead to pinching of the artery, nerves, and vein that course underneath the muscle.
• Shoulder pain. Since the pec minor muscle attaches to your shoulder blade and works to move your shoulder complex, it may be implicated in episodes of shoulder pain. Tightness in your pec minor may lead to poor postural control and decreased shoulder movement. This decrease in shoulder movement while lifting your arm may pinch the muscles of your rotator cuff and subacromial bursa, leading to pain.
• Pectoralis minor syndrome . A shortened and hypertonic pec minor muscle can cause problems with normal shoulder motion and pain or tingling sensations in your arm, forearm, or hand. Weakness in your forearm and hand may also be present. Symptoms of pectoralis minor syndrome may mimic those of thoracic outlet syndrome, so a careful examination by your physician is in order to determine if your pec minor is implicated in your symptoms.

If you suspect you have an injury or problem involving your pectoralis minor, you should check in with your physician. They can give you an accurate diagnosis of your condition and help guide you in finding the right treatment. You may benefit from working with a physical therapist to help you recover from your injury.

Treatments for pec minor injuries may involve several components. Keep in mind that you should visit your physician or physical therapist before performing any self-care treatments for your pec minor.

If your pec minor is tight or in spasm, heat may be used to help improve blood flow and relax the muscle. Applying heat to the muscle can also help decrease pain. Heat can be applied to the front of your shoulder for 10 to 15 minutes several times each day. Care should be taken not to burn your skin while applying heat.

Ice is often used to help decrease pain and inflammation in tissues in your body. If your pectoralis minor is inflamed and painful, ice may be used to manage the inflammation. Ice should be applied to the front of your shoulder for 10 to 15 minutes several times each day. Once the inflammation is under control, switching to heat for your pec minor may be indicated.

A shortened or hypertonic pectoralis muscle can pull your shoulders forward, giving you a rounded posture. It may also cause pain in the front of your shoulder and can limit shoulder motion. Massage to the pec minor can help decrease spasm in the muscle, allowing it to move and stretch normally. Massage to pec minor may be painful; the muscle lies beneath pectoralis major and is often difficult to get to with massaging hands.

If your pectoralis minor is tight, your physical therapist may prescribe stretching exercises to loosen it up. Easy stretches for your pec minor may include:

• The doorway stretch. Stand in a doorway, and place your arm out to the side with your elbow bent 90 degrees. Place your elbow against the door jamb, and then slowly lean forward. You should feel a slight pulling sensation in your chest. Hold the stretch for 30 seconds, and then relax. Repeat the stretch three times.
• The supine pec stretch. Lie on your back near the edge of your bed. Raise your arm up overhead, keeping your palm facing the ceiling. Make sure your arm is about 8 inches away from the side of your head. Then, allow your arm to fall gently down towards the floor until a stretch is felt in your chest. Hold the stretch for 30 seconds, and then relax. Repeat the stretch three times.

Stretching for your pectoralis minor can be done several times each day. Just be sure the stretches cause a pulling sensation; pain in the front of your shoulder should be avoided.

Shoulder pain is often caused by weakness around the muscles of your scapula, and the pec minor may be one of those muscles. Since the pec minor is so small, is often gets worked while strengthening other muscles around your shoulder. Strengthening exercises that can help your pectoralis minor may include:

• Shoulder internal rotation
• Shoulder scapular stabilization exercises
• Shoulder proprioceptive neuromuscular facilitation diagonal patterns

Strengthening exercises for your shoulder and pectoralis minor are often done three to five times each week.

If your pectoralis minor is tight, it may pull your shoulder blades forward, giving you a "forward head and rounded shoulders" posture. Correcting your posture may be prescribed. Postural correction techniques may include:

• Using a lumbar roll while sitting
• Performing scapular stabilization exercises
• Performing the slouch-overcorrect procedure

One of the best ways to correct your posture is with frequent reminders. Set an alarm on your phone to ring every hour, and when it does, sit up straight and maintain that good posture.

If you are suffering from pectoralis minor syndrome and are experiencing numbness or tingling in your upper extremity or hand as a result, you may benefit from nerve gliding exercises. These exercises gently "floss" the nerves of the brachial plexus, allowing them to glide and slide normally through the tunnel created by your pec minor and ribs.

The three nerve glides for the upper extremity include:

• The median nerve glide
• The ulnar nerve glide
• The radial nerve glide

These nerve stretching exercises may cause a slight increase in tingling in your hand or arm; the tingling should subside within minutes of stopping the exercise.

Injections directly into the pectoralis minor muscle are rare, but they may be done to diagnose painful problems with the muscle. Your doctor may inject lidocaine into the pec, blocking the nerve signals from the muscle. If the injection eliminates your pain, then your doctor knows that pain is coming from there and can direct treatments to your pec minor. Injections may also be used to decrease spasm and tone in the muscle; again, these are rare and are often used as a last-line treatment for pec minor problems.

Many injuries to the pec minor resolve within six to eight weeks of starting treatment. Your specific situation may take a bit longer, or it may be shorter. Be sure to work closely with your medical provider to understand what to expect from your pec minor rehab.

Your pectoralis minor muscles are major stabilizers of your shoulder girdle and may help with respiration. Understanding how these muscles function and their anatomy can help you get the right treatment after injury.