Shoulder impingement syndrome (rotator cuff injury) occurs when the tendons of the rotator cuff and the subacromial bursa (sac filled with lubricating fluid) are squeezed between the humerus and the acromion. Shoulder impingement syndrome causes persistent pain, especially when reaching up or back. The rotator cuff tendons and bursa can become inflamed causing tendonitis or bursitis. Left untreated, the tendons can thin or tear.
Understanding the Shoulder Joint and Musculature
To understand impingement, it’s important to understand the anatomy of the shoulder joint: shoulder joint, rotator cuff, and bursa.
The shoulder joint is what is known as a ball-and-socket joint. It is comprised of three bones: the humerus (upper arm bone), shoulder blade (scapula), and collarbone (clavicle). The head of the humerus fits into a shallow socket in the shoulder blade. A network of soft tissue (ligaments, tendons, and muscles) called the shoulder capsule surrounds the joint. These things work together to produce shoulder movement.
The rotator cuff is a group of tendons and muscles in the shoulder, connecting the humerus to the scapula. The rotator cuff tendons provide stability to the shoulder and the muscles allow the shoulder to rotate. There are four muscles that comprise the rotator cuff: teres minor, infraspinatus, supraspinatus, and subscapularis. Each muscle of the rotator cuff inserts at the scapula, and has a tendon that attaches to the humerus. Together, the tendons and other tissues form a cuff around the humerus.
The bursa is a sac filled with lubricating fluid, located between tissues such as bone, muscle, tendons, and skin. Its job is to decrease rubbing, friction, and irritation.
What Is Shoulder Impingement (Rotator Cuff Injury)?
Impingement is a condition that occurs when the tendons of the rotator cuff and the subacromial bursa are squeezed between the humerus and a nearby bone called the acromion. The condition causes persistent pain and impacts everyday activities, such as reaching for things or even getting dressed.
With impingement, the tendons and the bursa are pinched and then they become inflamed and swollen, which leads to more pain. This pain becomes worse when the arm is raised.
Causes of Shoulder Impingement Syndrome (Rotator Cuff Injury)
Shoulder impingement is often caused by repetitive motions, particularly overhead activity. Activities which have a higher risk of producing shoulder impingement include:
- Sports, such as swimming, baseball, volleyball, tennis, weight lifting, tennis, surfing, and water polo
- Painting (particularly high walls or ceilings).
- Stocking high shelves repeatedly
Factors which may contribute to shoulder impingement:
- Narrow space between tendons and bones: Structural abnormalities, arthritis, and bone spurs can result in a narrower space in which the rotator cuff and bursa can move, making them more likely to get pinched.
- Inflammation: Overuse or repetitive irritation can lead to inflammation and swelling. This inflammation alone can be painful, but becomes exacerbated when it leads to impingement.
- Bone and joint abnormalities: Structural abnormalities can result in a narrower space between the tendons and the bones. Some people are born with a curved acromion, which narrows the space, but others develop arthritis and bone spurs, which can also narrow the space. When there is less room for the rotator cuff and bursa to move, they are more likely to get pinched.
- Shoulder instability: The shoulder is the most mobile joint in the body, but that mobility comes with a price—instability. Underlying shoulder instability is a common cause of impingement in young athletes.
Symptoms of Shoulder Impingement Syndrome
The onset of symptoms is typically related to an episode of overuse and the symptoms progress over time. The main symptoms of shoulder impingement are:
- Pain with overhead arm use
- Difficulty reaching up behind the back
- Shoulder weakness
- Decreased range of motion
- Left untreated, the condition can lead to rotator cuff tendonitis, bursitis, or rotator cuff tear
- Pain associated with shoulder impingement
- Difficulty reaching up behind the back
- Pain with overhead use of the arm
- Shoulder weakness
- Decreased range of motion
- Left untreated, the condition can lead to rotator cuff tendonitis, bursitis, or rotator cuff tear
Pain associated with shoulder impingement syndrome (rotator cuff injury):
- In the early stages, pain is sharp and intermittent
- The onset of pain is often gradual and occurs in the front or side of the shoulder
- As the condition progresses, pain becomes a constant ache
- Over time, simple movements become painful (as inflammation increases)
- Reaching and overhead motions increase the pain
- Sometimes the pain radiates down into the upper arm
- Arm movements at waist level are not painful (due to less compression)
- Pain increases at night (and many people have difficulty sleeping on the shoulder)
Diagnosing Shoulder Impingement
Diagnosing shoulder impingement involves a physical examination by your doctor which may include:
- Muscle tests to determine if rotator cuff is torn
- Manipulation of the arm to identify pain triggers
- X-ray and MRI may be recommended
Treatment for Shoulder Impingement
Shoulder impingement can be successfully treated with:
- NSAIDs: 6-8 week regiment.
- Physical therapy
- Avoidance of repetitive overhead activity
- Corticosteroid injection: If other treatments are unsuccessful.
- Subacromial decompression: In rare cases, a surgical procedure is performed which expands the space between the acromion and the rotator cuff tendons.
Most shoulder impingement patients recover fully within a few weeks, depending on symptom severity and treatments.
Our goal at OSMI is to provide our patients quality, cutting-edge orthopedic treatments, both surgical and non-surgical. If you have questions about total joint replacement surgery, joint pain, or physical therapy, please submit an online appointment request or contact our office at 817-529-1900.
