When the Mets’ Matt Harvey left the game last Wednesday after 58 pitches over four innings, he complained of a tired arm. An MRI and CT scan led to the diagnosis of a stress injury in his right scapula (shoulder blade). Though some media reports assumed the injury to be a “broken bone”, SI.com noted that Harvey had sustained a “stress reaction”. They are not one and the same.

Harvey’s velocity, already trending downward, was lower still on Wednesday, with his fastball averaging 91.83 mph. There was obvious cause for concern.

Since his great comeback in 2015 after returning from Tommy John surgery (October, 2013), Harvey has had a rough time. He came into this season following a procedure last July to remove a rib to decompress the nerve in the thoracic outlet. The condition, thoracic outlet syndrome, had caused Harvey to experience numbness, tingling and coldness in his right hand, all of which resolved following the procedure.

Distinguishing a stress reaction from a stress fracture

Stress injuries result from overuse and cumulative localized fatigue. A stress reaction is characterized by bony abnormalities that stop short of cracking the outer shell of bone known as the cortex. It is a precursor to a stress fracture, in which the cortical bone is fractured.

Stress injuries are suspected when there is pain of unknown origin, occurring in the absence of trauma. An athlete who continues to train or compete with a stress reaction will likely go on to have it progress to fracture.

Though stress injuries occur much more commonly in the lower extremities – due to the loading that occurs with weight bearing – the occurrence of upper extremity stress fractures in athletes is not entirely rare. One study demonstrated that the location of these injuries correlates with the type of sport played. Those bearing weight through the uppers (gymnasts, cheerleaders, divers) typically experienced stress injuries distal to (below) the elbow. Throwers (pitchers, soccer goalies, javelin throwers) had the majority of their stress fractures in the shoulder girdle, and athletes who swung an implement (golfers, tennis players) suffered more rib injuries. Weight lifters (football players, lifters, wrestlers) exhibited no particular pattern to their stress injuries.

A little anatomy

The bones of the shoulder complex include the scapula (shoulder blade), the clavicle (collar bone), the sternum (breast bone), ribs and the humerus (bone of the upper arm).

The scapula provides an anchor for the 17 muscles that attach to it. These muscles include those of the rotator cuff.

The two bony extensions of the scapula that serve as palpable landmarks are the acromion which is like a hood over the shoulder joint, and the coracoid process that projects just below the outer clavicle.

There are four articulations in the shoulder complex. Though there is no bony connection to the thorax on which it lies, the first of these is known as the scapulothoracic joint. The others are the glenohumeral (shoulder), the acromioclavicular, and the sternoclavicular joints.

Pitching and stress injuries

Though healthy bones respond to exercise by remodeling, creating new bone growth, when bony and muscular demand surpasses capacity the result is breakdown. This can occur with excessive or rapidly accelerated training, or with insufficient rest between bouts of strengthening so as not to allow for recovery.

Muscle fatigue due to weakness or repetitive / prolonged overuse can contribute to the undue stresses at the bony attachments. Hence training to optimize muscular endurance is as important to performance as strengthening.

The uncompensated forces that can result when muscle imbalances are in play can also be an issue. When a muscle functions sub optimally, its counterpart may be disproportionately strong, compounding the stress.

With the extreme demands that pitching places on the shoulder girdle, it is actually somewhat surprising that scapular stress fractures don’t occur with greater frequency. Muscles with scapular attachments act in every phase of the motion.

The Scapula muscles

The proper activation and recruitment patterns of muscles that stabilize the scapula enable normal and safe movement at the shoulder joint. When muscular weakness or inhibition occurs, functional deficits and subsequent injury can result. Inversely, injury in the shoulder complex can interfere with these normal patterns at the scapula, also leading to deficits and further insult.

The muscles responsible for scapula stabilization, as well as many of those controlling shoulder motion attach to the scapula.

In the pitching motion, “An intricate relationship between the dynamic stabilizers (rotator cuff, pectoralis major, and latissimus dorsi) and static stabilizers is required to simultaneously supply the range of motion, force, and stability of the glenohumeral joint. This integrated effort relies on the trapezius, rhomboids, levator scapulae, and serratus anterior muscles for stabilization, positioning, and synchronous scapular motion. The scapula acts synchronously with the rotator cuff to maintain the glenohumeral center of rotation within a physiologic range during the pitching motion.”

The above was excerpted from a wonderful article, The Kinetic Chain in Overhand Pitching, which goes on to break down and detail the specific demands of the six phases of the pitching motion. It is easy to see why even repetitive normal mechanics – not to mention those that are dysfunctional – so easily result in injury.

As for Matt Harvey? Look for about a four to six week period of rest (depending on the severity of the injury and the healing response), followed by a rehab and throwing program. He’ll be out awhile.

About the author

Abby serves as the Injury Expert for CBS New York where, since 2010, her Injury Breakdown Blog examines injuries in professional sports. She also blogs on health & fitness as well as sports injuries for Huffington Post, and Recovery Physical Therapy.com, where her blog earned a top ten mention for physical therapy blogs in 2012 @ WorldWideLearn.com. In a ranking of the Top 30 Healthcare Blogs for 2012, Top Masters in Healthcare also rated Abby’s blog in the top three in Physical Therapy! Abby is the founder of Fit-Screen and she welcomes your comments and questions!