The subscapularis muscle belongs to a group of muscles and tendons in the shoulder area called the rotator cuff. The rotator cuff muscles help to lift and rotate the arm and stabilize the shoulder socket joint. All four muscles attach to the scapula in the back and the humerus or the upper arm bone in the front of the body. Unfortunately, rotator cuff tears are a common injury. The supraspinatus muscle is most commonly torn but the other cuff muscles, including the subscapularis muscle are also susceptible to injury.
Observation
The simplest test for rotator cuff problems is observation. A basic shoulder exam includes demonstration of the range of motion and arm strength. Additionally, the physician palpates the shoulder to isolate areas of pain or tenderness. The physician also looks for soft tissue changes such as swelling or redness in the shoulder area. While observation may help determine whether or not the problem lies in the rotator cuff, other tests are needed to isolate the affected muscle.
Belly Compression Test
The "belly compression" or Napolean test assesses the subscapularis muscle. The patient places her hand over her stomach with the palm facing the belly button. The physician places his hand in between the patient's hand and stomach and pulls outward while asking the patient to pull her hand toward the belly button. If the test is positive, the patient will experience pain or weakness indicating a possible subscapularis tear, lesion, or tendonitis.
Lift-Off Test
A second diagnostic test for assessing the subscapularis muscle is called the "lift off" or Gerber's test. The patient places his hand in the small of his back with the palm facing outward. The physician exerts pressure on the the patient's palm with his hand while asking the patient to push outwards. If the test is positive, the patient will experience discomfort indicating a possible subscapularis tear, lesion, or tendonitis.
Imaging Studies
Based on the physical exam, the physician may order imaging studies to confirm his diagnosis including X-ray, ultrasound and MRI. MRI is particularly useful for visualizing soft tissue making it a helpful tool for diagnosing muscle or tendon tears and lesions.
