Four muscles make up the rotator cuff. Your doctor may refer to them by the abbreviation SITS, which stands for supraspinatus, infraspinatus, teres minor, and subscapularis. These muscles originate from the scapula, also known as the shoulder blade; their respective tendons come together as a cuff attached to the top of the humerus, or upper arm bone. These muscles work together with one another and with nearby, larger outer muscles, including the deltoid, to lift and rotate the arm. A torn rotator cuff means that one or more of these tendons has torn.
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Tears are described as partial thickness, which means the tendon is damaged but still attached to the humerus, or full thickness, in which the tendon is completely detached from the humerus. Full-thickness tears may involve just a single tendon, usually the one attached to the supraspinatus, or multiple tendons. Doctors also measure tendon retraction, the distance the tendon has separated from the bone, and the tear pattern, the shape of the tear.
Rotator cuff tears tend to occur in older patients who have degenerative tissue in which the collagen, a protein, has weakened. Collagen is essential to strengthening tendons and other tissues.
Symptoms of torn rotator cuff include shoulder pain, especially at night; difficulty lifting the arm above the shoulder level and reaching behind the back; a grinding or popping noise when you move your shoulder; and weakness in the arm. A torn rotator cuff can also interfere with the activities of daily living, such as dressing and taking a shower.
Doctors at NYU Langone use a physical exam and imaging tests to diagnose a torn rotator cuff.
During a physical exam, your doctor takes your medical history and asks you about your sports, recreation, and daily physical activities. You are also asked about your symptoms and whether they are interfering with daily living. Your doctor may also palpate—touch and press—the tissue around the shoulder and assess the range of motion of the joint.
Your doctor uses imaging tests to help diagnose a rotator cuff injury. An X-ray helps to rule out bone spurs or osteoarthritis as a cause of your symptoms. An MRI scan enables your doctor to see the soft tissue in the shoulder and determine if you have a rotator cuff tear and whether it is partial or full thickness. An MRI can also provide doctors information about the tendon retraction or tear pattern, which may influence decisions about what surgical techniques to use. Ultrasounds also create picture of soft tissue and give your doctor real-time information about the tendons and muscles of the shoulder as it is placed in various positions.
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