The shoulder is the most complex joint in the body. It has the greatest range of motion of any joint in the body and in doing this it gives up stability for range of motion. Therefore, it has to be stabilized by a number of factors which all work together to allow the smooth functioning of this joint.
Anything that affects one of these stabilizing or mobility components may lead to the type of pain that is common and felt by many of us. The bony components are the humeral head which articulates with the glenoid fossa of the scapula i.e. the socket that is housed on the “shoulder blade”. The large head in the shallow socket has to be stabilized by the rotator cuff muscles, the four of which originate on the scapula and hold the head in the centred position in the socket and allows the larger shoulder muscles : deltoid, pectoralis, latissimus dorsi and the trapezius , to move the arm. The scapula itself is stabilized and moved to enable the arm to be positioned in various locations by the para-scapular muscles such as the rhomboids and the levator scapulae.
The whole process has to be well coordinated to allow us pain free function of the shoulder. Additonally, the nerves which go to the arm and hand ( from our cervical spine) pass just under the shoulder joint via our “arm-pit” and a pinched nerve in our neck may lead to pain being felt in our shoulder: a radicular type pain, that is perceived as coming from the shoulder but really originates in our neck.
In-coordination of the muscular mass that controls our shoulder and arm movements may lead to the muscles or tendons rubbing on the undersurface of the acromion process ( i.e. the hard bone just under the tip of the shoulder) and cause impingement syndrome which is an inflammatory condition that may lead to pain in certain arm positions and a nagging pain that is worse at night. This process may progress to the stage where our bodies ( some people are more susceptible to this phenomenon) lay down calcium deposits in the irritated tendon that leads to calcific tendonitis. The hallmark of this calcific tendonitis of the shoulder is acute flare ups of pain for no apparent reason:
“I haven’t done anything unusual or injured my shoulder so why is it paining so much?”
Further, chronic impingement may lead to a wearing out of the tendon ( commonly the supraspinatus tendon ) and to an actual rotator cuff tear which may result in a loss of motion of the arm or prior to this pain with use of that arm in an overhead position such as hanging clothes on the line or putting objects into a high cupboard. Some people may be affected by a painful shoulder and loss of motion due to “frozen shoulder” which is a completely different condition due to a “seizure “ of the joint that affects females mainly especially in the 5th decade, diabetics, people who have had trauma or operations to the arm.
Your Orthopaedic Surgeon will be able to consult with you, examine your shoulder and review the relevant investigations to determine exactly what is the cause of your shoulder pain so that the appropriate treatment can be applied to relieve the pain and improve the function of your shoulder.