|Your shoulder may be completely painfree most of the time, but on certain movements, usually out to the side or overhead, it gives a sharp pinching pain, that eases immediately the action is stopped. |
The generic term for this type of shoulder presentation is ‘Thrower’s’ or ‘Pitcher’s’ Shoulder (as you can imagine, it was first given this title in America!). The condition is most commonly seen in the early summer, associated with coming out of winter hibernation to play ball/ tennis/ rounders and such in the park on fine summer evenings. This year we have noted several incidences of Thrower’s Shoulder from intense sessions of tennis on the newest electronic craze, the Wii fit.
So what is this condition and why does it develop? As in many musculoskeletal conditions, it all starts with basic anatomy. The shoulder is the most mobile joint in the body. As you may remember from Junior Cert biology, is a ball and socket joint, with freedom to move through 360 degrees. The shoulder girdle is made up of three interconnected bones and joints: the clavicle or collarbone, the scapula or shoulderblade and the humerus or upper arm bone.
It is ligaments and muscles of the upper arm that keep the ball and socket joint together, otherwise the arm would just fall uselessly out of the socket. A particularly important group of muscles comes from the shoulderblade, travels under the bony point of the shoulder to attach onto the top of the upper arm. This group of four muscles is known as the rotator cuff. The fact that it lies in a bony arch or tunnel between the top of the upper arm bone and the point of the shoulder is a clever architectural or anatomic design, but it also puts the muscle at risk of injury over time.
This small but vital muscle group is involved in every action of the shoulder, controlling alignment of the arm bone with the socket. The fine control provided by these muscles allows for repeated accuracy in delivery in throwing or racquet sports. As the throwing action is repeated again and again, these muscles work in a confined bony space where they are sensitive to compression from bone above and below. Occasionally through less than perfect sports technique or even a single bad throw or unguarded movement of the shoulder, the cuff of muscles becomes pinched and injured by excessive compression.
The primary injury response of all soft tissues is for the tissues to swell. This is fine in an ankle or knee, where there is room within the joint and overlying skin for the swelling to emerge. However in the small bony tunnel where the rotator cuff lives, there is minimal room for enlarged swollen tissues. In fact the swelling further compresses the muscle cuff, virtually doubling the effect of the original injury. This is the process that creates the painful pinching sensation classically seen in Thrower’s Shoulder. The pain is often around the tip of the shoulder, but not superficial, as the sore muscles lie under the bony tip of the shoulder rather than on the tip.
To make matters worse, once the rotator cuff muscles are painfully pinched, the pain switches off or inhibits larger muscles which clamp the shoulderblade onto the ribcage.
Free movement and strength of what we call collectively the shoulder is dependant for the most part by the mechanism whereby the scapula clamps onto the back of the ribcage, providing support for the mobile arm. The clamping ability of the scapula onto the ribcage is entirely muscular in origin. When pain from the tip of the shoulder switches off some of shoulderblade muscles the whole smooth motion expected of the shoulder region changes and becomes dysfunctional. In turn this has further negative implications for the rotator cuff muscles in their bony tunnel.
The special anatomical constraints of this area mean that once there is pain, ongoing damage is occurring to the muscles. If left untreated movement dysfunction of the shoulder worsens and leads to increasing and permanent degeneration of this small group of muscles in the bony tunnel. Most of us have no problem imagining how wear and tear affects our joints later in life, but wear and tear, or degeneration also affects muscles and in particular this rotator cuff of shoulder muscles. The muscles begin to wear out just like old worn fabric that has become thin and see-through. In severe cases surgery is necessary to attempt to re-stitch them together like darning old socks and, just as in socks, the repair is never as good as the original.
However, in the early stages Thrower’s Shoulder can be successfully treated with a combination of medication, steroid injection or electrotherapy to reduce inflammation. Manual therapy and exercise rehabilitation address the movement dysfunction, while a session with a sport coach can improve a less than perfect technique.
Though Thrower’s Shoulder is well described within medical and sports literature, similar painful pinching of the rotator cuff can occur outside of sports. Irrespective of origin, the same anatomical mechanism is at fault when pinching pain around the tip of the shoulder is present. So if you notice pain in this area, only associated with particular movements it is not a symptom you should ignore.