What is rotator cuff tendonitis?
Pain with activity (particularly overhead lifting) tends to involve the muscles and tendons, known as the rotator cuff, that surround the shoulder joint. A common condition, known as impingement syndrome, occurs when the rotator cuffbumps up against the overlying bone as the shoulder is raised (Fig 1). This process can be worsened by the shape of the overlying bone, known as the acromion. In particular, hooking or spurring of the acromion can decrease the available space for the rotator cuff to function. Like a rope rubbing against a rock, repeated contact causes damage to the tendon and/or muscle, causing rotator cuff tendonitis, which means inflammation of the tendon. If it goes on for long enough eventually the rotator cuff will progress to a partial or full thickness rotator cuff tear. There may be a specific inciting event, but most often the symptoms come on gradually.
Is my shoulder pain from rotator cuff tendonitis?
The shoulder joint is not a ball-and-socket joint like the hip. Rather, it is more like a golf ball sitting on a golf tee (Fig 2). This lack of bony constraint gives it more freedom of movement but also makes it more unstable. This is why it is so much easier to dislocate your shoulder than your hip! The rotator cuff muscles act to provide stability of the shoulder through coordinated action. This is known as dynamic stability. So a good starting point for shoulder pain is to determine if symptoms are at rest or with activity. Pain with movement is usually caused by damage to the rotator cuff, which usually starts off as rotator cuff tendonitis. Pain at rest is more serious and can mean the rotator cuff has progressed from tendonitis to a tear (other possibilities include arthritis, discussed in another post). The entire constellation of symptoms, including tendonitis and tearing, is known as rotator cuff syndrome.
What does rotator cuff tendonitis feel like?
Pain from rotator cuff tendonitis is usually located on the outside part of the shoulder and can radiate down the arm (Fig 3). Patients will notice that pain and weakness occur with certain overhead motions, along with a sensation of popping or crackling. With continued damage to the rotator cuff, symptoms can persist long after activity. If the damage to the rotator cuff is severe enough to cause a tear, symptoms generally include the above, plus pain at rest. With a cuff tear, a common complaint is the inability to sleep on the affected side.
How is the diagnosis of rotator cuff tendonitis made?
Fortunately, most conditions affecting the shoulder can be properly diagnosed with a thorough history and physical exam, performed by a clinician with musculoskeletal training and experience. After the initial evaluation, an imaging study (x-ray or MRI) may be needed to confirm the diagnosis (Fig 4). Of note, MRI’s are noninvasive, safe, and highly accurate at imaging soft tissue like muscle and tendon.
How is rotator cuff tendonitis treated?
Treatment depends on how damaged the anatomy is. If the rotator cuff is inflamed, but not torn, then physical therapy is usually the best option. Therapy goals are to improve the mechanics of the shoulder, which can eliminate the impingement. Sometimes a cortisone injection calms down the inflamed tendon, however, cortisone is usually not a long term fix and should only be used sparingly. Platelet-rich plasma injections (PRP) are currently popular and have little downside. Studies are ongoing to determine its effectiveness.
If conservative measures fail, then surgery should be considered. Often this is necessary if the cuff is torn and/or the acromion has a big spur that needs to be removed. The good news is that, if surgery is needed, most conditions affecting the shoulder can be addressed with an arthroscopic technique (Fig 5). Using a pencil-thin camera and instruments, repairs can be performed through small incisions, allowing the patient to go home on the same day of surgery. The success of surgery is closely tied to whether the rotator cuff is torn and if so, the size and age of the tear (if the tear is large and has been present for long enough, it will retract and undergo structural changes, making repair more difficult). Other factors which make cuff repair more difficult include age >65, diabetes, and smoking.
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Orthopaedic Knowledge Update (OKU) 11, Published by the American Board of Orthopaedic Surgeons, 2014, pp 357-371