Shoulder impingement syndrome is one of an array of conditions that indicates a dysfunction in shoulder mechanics. It frequently presents with rotator-cuff injuries and causes pain in the upper arm, decreased and painful range of motion, and interrupted sleep.

One possible culprit for impingement syndrome is the scapulohumeral rhythm, the coordination of the scapula in relation to the humerus during movement. There are two muscles that are prime-time players in this rhythm: the serratus anterior and the trapezius. But before looking at strategies and protocols for these muscles, it’s important to review the anatomy.

Shoulder Anatomy

The superior aspect of the shoulder joint is called the impingement area. The primary structures affected in impingement syndrome are the supraspinatus tendon, the subacromial bursa, and the long head of the biceps. When the humerus is internally rotated, the greater tubercle rolls forward, taking the supraspinatus tendon along for the ride. Since the supraspinatus attaches to the top of the greater tubercle, it will collide with the acromion process if the humerus is abducted in the internally rotated position (Image 1). Try internally rotating and abducting your humerus and you’ll feel the restriction of the greater tubercle colliding with the acromion process.

Just imagine how many times people do this on any given day. You can see why this muscle-tendon unit is so frequently torn and/or impinged (Image 2). The subacromial bursa lies above the supraspinatus and underneath the acromion process and, of course, it too suffers from irritation and inflammation when impinged.

As for the long head of the biceps, habitual internal rotation will cause that tendon to rub against either the lesser or greater tubercles, causing microtearing, impingement, and inflammation.

If you suspect impingement syndrome, you can test for it easily using the Hawkins-Kennedy Impingement Test (Image 3). Flex the client’s shoulder to 90 degrees. From that position, internally rotate and horizontally adduct the humerus across the chest as far as it will go. This brings the greater tuberosity of the humerus up under the coracoacromial arch, and it will press on the soft-tissue structures under the arch (the supraspinatus tendon, long head of the biceps, and subacromial bursa). If impingement syndrome is present, this test will reproduce the pain and discomfort.

The Likely Culprits

The shoulder girdle and shoulder joint dance a lovely duet, called the scapulohumeral rhythm. In order for the humerus to move beyond 30 degrees of abduction and 45–60 degrees of flexion, the scapula must move in order to accommodate the humerus. Upward and downward rotation of the scapula happens when the humerus is abducted more than 30 degrees or flexed more than 60 degrees. We’ll use abduction as our model. 

Image 4 shows the humerus abducted to 30 degrees and the scapula in neutral. As the humerus rises toward 90 degrees, the head of the humerus approaches the acromion process. In order to abduct the humerus more than 90 degrees, the scapula must get out of the way or else the head of the humerus will collide with the acromion process. Image 5 shows the scapula upwardly rotated, leaving a clear pathway for the head of the humerus. The dark gray scapula shows the scapula in neutral. Upward rotation refers to the acromion process, clavicle, and glenoid fossa rotating upward. 

Feel it on yourself by placing your fingers in the middle of your clavicle and walking your fingers laterally until they meet with the acromion process. Now, abduct your arm above 90 degrees and you will feel the acromion process and clavicle upwardly rotating. 

The serratus anterior and the trapezius are the prime movers for upward rotation of the scapula. Since these two muscles tend to be locked short (held in a concentric contraction), and fascially bound, they are likely candidates for impeding healthy rotator-cuff function and causing shoulder impingement syndrome.

A Scapulohumeral Rhythm Test

An easy way to determine if a client has scapulohumeral rhythm problems is to stand behind her and place one hand on her scapula. Ask her to slowly raise her arm above her shoulder. You will feel the upward rotation of the scapula. Now do the same thing on her other arm. The final step is to place your hands on both of her scapulae and ask her to raise both arms above her shoulders. Both scapulae should upwardly rotate at the same time. On someone who is having impingement symptoms, the affected scapula will lag behind the healthy shoulder. In other words, the upward rotation is not happening soon enough, and some irritation of those structures in the impingement area (the supraspinatus tendon, long head of the biceps, and subacromial bursa) is occurring. Over a long period of time, significant damage can occur. 

Working the Serratus Anterior

The serratus anterior is an important muscle for shoulder-girdle stabilization (holding the scapula on the torso to prevent “winging”) and torso alignment. When locked short, it pulls the scapula, shoulder, head, and neck forward and restricts the lateral movement of the ribs during respiration. Since the serratus and trapezius upwardly rotate the scapula, a tight and fascially bound serratus can limit painless and fluid abduction or flexion of the humerus when greater than 45–60 degrees. As we’ve seen, the humerus needs the scapula to upwardly rotate to avoid the collision of the acromion process and the head of the humerus.

Here’s a protocol for effectively addressing issues with the serratus anterior:

1. The client can be supine, side lying, or prone, but I find side-lying positions offer the most advantages for access. Have the client position her arm out of your way by propping it on a pillow. Start by skin rolling without lubricant, which helps to release the fascia.

2. To release the stubborn superior fibers of the serratus, place your fingers as if you were accessing the subscapularis. Instead of pressing toward the scapula, press your fingers on the upper ribs (Image 6). Your client’s arm can rest comfortably on your shoulder. You’ll find lots of trigger points and hot spots to release. Static compression and deep stroking are good choices here. The serratus lies on top of the ribs, not between, so you want your pressure to be directly on the ribs.

Include active movements to help your fingers “swim” into the tissue and gain depth. Have your client reach her arm across her body and back, protracting and retracting the scapula as you release trigger points and hot spots. Or, ask your client to abduct her arm more than 90 degrees to engage the fibers of the serratus that perform upward rotation.

3. Apply latitudinal stroking, anterior to posterior along the ribs, while taking the shoulder through both the passive and active range of motion described above. Locate tender spots and trigger points, and release them with static compression and deep stroking. Most tender areas and trigger points are found on the lateral ribs along the sight line of the nipple. Work the muscle from the ribs toward the shoulder blade, which promotes proper scapula placement. Encourage your client to breathe into the lateral ribs to expand them while you work.

4. Finish with a stretch of the serratus anterior, with the client in a side-lying position on the side opposite the one to be stretched. Press the shoulder blade into full adduction. This is a subtle stretch, but clients with a tight serratus will find it quite pleasant.

Working the Acromial/Clavicular Attachments of the Trapezius

Since the trapezius upwardly rotates the scapula, tightness here can limit abduction of the humerus when greater than 60–90 degrees. The trapezius is often the overlooked component in restoring full range of motion to the shoulder joint. Typically, the upper portion of the trapezius is more developed than the lower trapezius, which means the latter (that depresses the scapula) cannot balance the upward pull of the upper trapezius on the scapula and clavicle. The middle portion of the trapezius is often weak and overstretched due to a slumped shoulder posture. Both the middle and lower portions of the muscle usually benefit from strengthening exercises, which help stabilize the shoulder girdle and therefore release the load on the rotator cuff. The upper trapezius often gets enmeshed with the posterior scalene, which it sits on top of, in a dysfunctional relationship that inhibits healthy functioning of either muscle.

 Since most massage therapists are quite capable of releasing the trapezius, the following protocol focuses on working the acromial/clavicular attachments. Work the entire muscle, but concentrate on this usually overlooked area of “glued” tissue. Clients can be supine, side lying, or prone, but I find the supine position offers the best access. Concentrate your work in the small area around the attachments at the acromion process and the clavicle.

1. Skin roll the area, working to free this fascially bound tissue.

2. Perform deep parallel stripping, cross-fiber friction, and static pressure to free the attachments. Have the client do active movements to help your fingers “swim” into the tissue and gain depth while you work. Ask your client to abduct her arm more than 90 degrees to engage the fibers of the trapezius that perform upward rotation. Also, ask her to laterally flex the neck to the opposite side and return it to center.

3. Finish by stretching the trapezius with the client supine. Laterally flex the client’s neck, ear to shoulder, and ask the client to rotate her head away from the side of the neck being stretched. In Image 7, the therapist’s right hand is gently pushing the client’s right shoulder down while the left hand is gently pressing the head and neck toward the left shoulder. Traction the neck before and during the stretch.

If you have a client who is not responding to treatment, she may have a Type II or Type III acromion process. Type II acromion processes are curved and dip downward; Type III acromion processes are beaked. Both types obstruct the outlet for the supraspinatus tendon. This can easily be seen with an X-ray. In these cases, surgery may be the best option, especially for those with a Type III process. That being said, my impingement syndrome took a good year to resolve, and I have a normal acromion process. 

Combining massage therapy with other modalities such as ultrasound and acupuncture can produce a powerful therapeutic effect. Sleep position, posture, and body mechanics must be addressed for any treatment to be lasting. Regularity and continuity of treatment is essential for relief from shoulder impingement syndrome, and it’s wise to advise clients that healing may come in baby steps. 

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