There are 7 scapulohumeral muscles that connect the scapula and Humerus. The role of these muscles are to stabilize the glenohumeral joint as well as to move the arm through all planes of motion.
The 7 Scapulohumeral Muscles include:
1. Infraspinatus muscle
2. Subscapularis muscle
3. Supraspinatus muscle
4. Teres minor muscle
(The 4 Rotator Cuff Muscles)
5. Coracobrachialis muscle
6. Deltoid muscle
7. Teres major muscle
Assessing the Scapulohumeral Muscle Length
In order to assess the length of the scapulohumeral muscles, it’s important to first test the latissimus dorsi length. This gives you a ‘starting point’ or a baseline for shoulder flexion that you can expect to see during the scapulohumeral mucle length test.
The proper position to assess the length of the scapulohumeral muscles is in supine (lying face up) with knees flexed to 90˚.
- Lie face up on a flat surface with knees bent to 90˚.
- Passively flex one arm overhead, keeping the thumb pointed upward so the Humerus stays laterally rotated.
- Monitor for these compensatory motions: the lateral border of the scapula protrudes more than ½ of an inch from the lateral side of the thorax. Other faulty motions may include scapular posterior tilting, anterior displacement of the humeral head, or excessive scapular abduction.
- Apply a correction to a protruding scapula by placing the arm in 90˚ shoulder flexion. Apply a manual pressure to the lateral border of the scapula so that it dos not protrude more than ½ inch from the thorax.
- With this pressure, passively flex the shoulder overhead and note if the range is less than the range achieved during the latissimus dorsi test (remember the baseline range of motion.)
- At the end range, medially rotate the Humerus. If greater range is achieved, then the teres major is a primary contributor to the shortness.
Interpreting the Results
Decreased Range: If you are not able to achieve the same range as the latissimus dorsi test, you have found the scapulohumeral muscles to be short.
More Range with Medial Rotation: If greater range is achieved when the arm is medially rotated, the teres major is the main scapulohumeral muscle that is short. (If no change is found with medial rotation, then all of the scapulohumeral muscles are considered short.)
Understanding the relationship between the scapulohumeral muscles and their length and flexibility can help to isolate the primary muscles involved in a restricted pattern of motion.
Stretching The Scapulohumeral Muscles
If the lateral rotators or posterior capsule is tight, the following motions can be used as a stretch. I’ll list two here and welcome more within the comments!
Prone Medial Rotation – Position yourself face down on an elevated surface with the humerus in line with the scapula so that your arm is in a 90˚/90˚ position (use a towel roll to support humerus). Perform pure medial rotation without pressing your shoulder into the towel roll (rotate your arm so your fingers are pointing towards your feet). Pure medial rotation is a conservative way to stretch the lateral rotators.
Horizontal Adduction – You can perform this motion while lying on your back, standing, or in a chair. Raise your arm to 90˚/90˚ (shoulder and elbow flexion) and turn your arm so that it’s parallel to the ground (palm facing down). With your other arm, gently pull your elbow towards the midline of your body while trying to keep the scapula from moving. This might require support from the back of a chair or even lying on a surface so the scapula is blocked.
What other stretches would you suggest to help lengthen the scapulohumeral muscles?