What is rotator cuff tendinosis (tendinopathy)? What are the consequences of labeling it as “tendinitis"? What are the consequences of labeling rotator cuff tendinopathy as a “partial rotator cuff tear”? What are the consequences of labeling rotator cuff tendinopathy as “impingement syndrome”?
Rotator cuff tendinosis (tendinopathy) is a clinical shoulder condition, usually associated with tendon degeneration, leading to pain with movement. The supraspinatus tendon is usually the focus of the condition, and thus overhead activity is usually the motion that is particularly painful, rotator cuff tendinitis. Rotator cuff tendinosis is produced by a combination of repetitive use, poor blood supply to the distal end of the tendon, and generalized senescence (age-related degenerative change).
Rotator cuff tendinitis
Rotator cuff tendinosis is more commonly known as Rotator cuff tendinitis.
Sticklers would be correct to say that the condition is more aptly named tendonosis, as the “-itis” suffix misleadingly suggests that the condition is inflammatory, which it is not. Referring to this condition as an “-itis” may in turn compel treatment aimed at inflammation, which is not necessarily needed. While anti-inflammatory medication can be helpful in the management of pain associated with rotator cuff tendinitis, they are effective because they are (also) analgesics and not necessarily due to their anti-inflammatory properties.
Partial rotator cuff tear
Because there is usually some fraying of the tendon seen in the setting of degeneration, rotator cuff tendinopathy may be read on an MRI as a “partial tear” of the cuff. That nomenclature is unfortunate, because it suggests a condition inflicted by trauma (“tearing”). Also, to some, the name connotes something in need of repair. (If it’s torn, you mend it.)
If one encounters a diagnosis of a “partial thickness rotator cuff tear” in the setting of degenerative tendinopathy, the second word “tear” is best interpreted as it would be in the idiom “wear and tear.”
Impingement comes from the Latin word meaning “to press upon” and indeed, years ago, it was thought that tendinitis was caused by pressure from the acromion. This ‘pressing upon’ theory makes intuitive sense: the pain experienced by patients with rotator cuff tendinopathy is worse with overhead arm movement, which is a position in which the supraspinatus is more apt to be, well, impinged, by the acromion (Figure 1). Moreover, there seems to be an association between larger acromial spurs and tendonitis.
Attributing rotator cuff tendinitis to impingement, however, can lead to unnecessary acromioplasty (Figure 2), a very popular operation years ago. It is now understood that there may be a causal link, but the arrow is pointing the other way around: acromial spurs are formed in response to the tendonitis, but do not cause it themselves.
Figure 1: Supraspinatus tendon path to insertion on humerus as seen on MRI: it sure does look like the acromion (noted by the red star) can “impinge” on this tendon. Note also the heterogeneous signal (mixed light and dark color) in the tendon, the region identified by the yellow arrow. This clearly shows that the damage is internal (modified from Radiopedia https://radiopaedia.org/cases/supraspinatus-tendinosis-1>)
Figure 2: Illustration example of acromioplasty. Shown on the left is a “Y” view (true lateral) of the shoulder. In a Y view, the body of the scapula forms the base of the Y, and the spine of the scapula and the coracoid form the left and right limbs, respectively, of the top of the Y. The acromion is a continuation of the spine of the scapula (shown on the left limb of the Y, highlighted by the red arrow). This particular acromion is slightly hooked (with an anterior spur). Removal of the spur is depicted on the radiograph to the right. (The x-ray image before annotation is borrowed from https://radiopaedia.org/cases/normal-shoulder)