In many cases of stubborn and difficult-to-treat shoulder pain that is accompanied by loss of motion, the subscapularis muscle is often the hidden source. Understanding the role of the subscapularis muscle in shoulder movement and proper treatment of this muscle are extremely important in addressing the root cause of many lingering shoulder conditions that are not responding to treatment.
The subscapularis is often involved in many patients experiencing shoulder problems, but is often overlooked in treatment. Therefore, it is important to routinely check this muscle, particularly when working with patients who have difficulty lifting their arm overhead or reaching behind their back. The subscapularis should also be examined when treating supraspinatus tendonitis, frozen shoulder or shoulder impingement conditions. Treating this muscle is often the key to completely restoring full range of motion for those conditions.
The subscapularis muscle is one of the four rotator cuff muscles, but is less accessible to palpate and needle than the other rotator cuff muscles. The thick belly of the subscapularis is located on the anterior surface of the scapula and fills almost the entire front surface of the shoulder blade. The subscapularis tendon passes across the front of the shoulder joint and attaches to the humerus at the lesser tubercle between the biceps tendons and deep to the deltoid muscle. This means the bulk of the muscle lies between the ribs and the scapula. It is essentially sandwiched between the serratus anterior and pectoralis major muscles on the anterior and the teres major and latissimus dorsi muscles at the posterior.
Its action is to internally rotate and adduct the humerus, which means that this muscle is activated with swinging the arms across the body while walking, forehand and backhand tennis strokes, throwing, rowing, swimming (front crawl) and in a rounded shoulder posture. The other important function of the subscapularis is to pull the head of the humerus downward and compress the head of the humerus in the glenoid fossa. This prevents the head of the humerus from moving too far superior and anterior in the shoulder joint when the arm is raised. Imagine the origin of the subscapularis pulling closer to the insertion on the greater tubercle. This line of force pulls the subscapularis into the shoulder joint. When the subscapularis becomes hypertonic, the humeral head is compressed into the glenoid fossa resulting in loss of motion (abduction and lateral rotation). Tension and trigger points in this muscle can cause painful and progressive loss of shoulder motion resulting in symptoms of frozen shoulder. Conversely, when this muscle is weak, the humeral head moves too far upward and forward leading to shoulder instability, supraspinatous tendonitis and impingement syndrome. Interestingly, in activities such as a tennis or volleyball serve, pitching a baseball, or swimming the front crawl, the subscapularis elongates under tension (eccentric contraction) and then rapidly contracts (concentric contraction) during follow-through. The subscapularis has more potential to become injured during these activities.
Signs of subscapular involvement include pain with both activity and rest, difficulty lying on the affected side, difficulty completely raising the arm overhead or reaching behind the body, pain with throwing. Examination of the shoulder will show loss of range of motion with abduction and lateral rotation and weakness and/or pain with resisted medial rotation and an abnormal lift-off sign. Trigger points in the subscapularis muscle refer pain to the anterior and posterior shoulder, scapula, posterior arm and can wrap around the wrist (SI, TB, LI and HT meridians).
Because of its location, the subscapularis can be challenging to find and treat.
Distal points may not be consistently effective and local needling can be risky. Manual soft tissue release may the preferred method of treatment. Manual therapy also provides a more thorough release of the muscle and tendon. To treat this muscle position the patient supine with the arm abducted to 90 degrees (less if it is uncomfortable for the patient). Place the patient's arm into a comfortable position of external rotation and support it with a pillow or towels. The practitioner is standing level with the patient's chest. With the lower hand the practitioner places the index finger just below heart 1 and gently presses with the pads of the fingers onto the anterior surface of the scapula until tissue resistance is felt. The practitioner places her upper hand at the posterior surface of the scapula and tractions it laterally. With this tractioning, more of the subscapularis is exposed and the lower hand will be able to slide more deeply onto the anterior surface of the scapula. Press statically for approximately 10 seconds.
If the patient experiences tingling or numbness, the practitioner is compressing the nerves and blood vessels of the thoracic outlet and needs to shift the lower hand inferiorly. Repeat this process by moving down the subscapularis in 1-inch intervals until the entire muscle has been treated. Repeat once more. Next, to further lengthen the muscle and break up any adhesions, the patient adducts her upper arm across her body. The practitioner then contacts the subscapularis and the patient actively moves her arm into abduction and external rotation by moving her arm over her head. Repeat in intervals until the entire muscle has been covered. The practitioner should always work within the patient's comfort zone. To treat the tendon attachment, find the head of the lesser tubercle which is located approximately 1-inch lateral to the coracoids process. Press between the two tendons of the biceps brachii and deep to the deltoid. The subscapularis tendon attaches to the medial surface of the lesser tubercle and can be very tender. Use short strokes in the direction of the fibers moving lateral to medial and then cross fiber moving superior to inferior. Afterwards, stretch all the muscles of the rotator cuff. It is important to remember that this muscle can be exquisitely tender and to always work within the patient's comfort zone. Do not over treat. After treatment the area may feel sore and tender to the touch. This reaction can be reduced by applying blood moving salves or liniments to the area or applying moist heat immediately after the manual release.
In Chinese medicine, the axilla is considered the doorway for the circulation of qi and blood through the arm. Blockages must be cleared in order for qi and blood to flow freely and nourish the upper extremity. Taking a small amount of extra time to examine and treat the subscapularis will reap big rewards in alleviating pain and restoring normal range of shoulder motion.
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