Rotator Cuff Tendiniti, Bursitis, Impingement


Bones & Joints

The primary joint in shoulder is a ball and socket joint.    The ball side of the joint is convex and is part of the arm bone (humerus).   The socket side of shoulder blade is very shallow (concave) and is part of the shoulder blade (scapula).

Above the ball and socket joint is the roof of the shoulder.     It is also formed by 2 bones:   the tip of shoulder blade (acromion) and the collar bone (clavicle).      The roof is a secondary joint and has very little movement.

Therefore,  in terms of bones & joints, the shoulder has 3 layers:

  1. The Roof,
  2. The Space under the Roof,  +
  3. The Ball & Socket Joint.


The shoulder joint is stabilized by a group of muscles called the Rotator Cuff.     The rotator cuff is not one muscle but the group name of 5 different muscles/tendons which is part of this group.    As a group,   these muscles/tendons work to stabilize the shoulder joint from front, back, and under the roof.

In addition to working as a group,  each individual muscle/tendon is aligned and has a primary function to move the shoulder joint into a specific direction.    For example:


A common problematic area is in the space under the roof of shoulder:

Due to amount of friction either from wear & tear from overuse or acute injury,   muscles of the rotator cuff and/or the bursa (water cushion designed to reduce friction) under the roof can be injured leading to tendinitis, and/or bursitis respectively.      If swelling and inflammation is sufficiently severe,   impingement can occur under the roof causing considerable difficulty and pain in elevating arm from side and front:


  • Pain and spasm
  • Difficulty in lifting arm above shoulder height (front and side) and behind back
  • Painful Arc caused by impingement
  • Weakness
  • Difficulty with functional activities involving arm  (i.e. reaching overhead, shower, combing,  laying on side, etc.)


A comprehensive diagnosis can be synthesized by combination of history,  physical examination, and diagnostic imaging.  Commonly used diagnostic imaging techniques include x-rays, diagnostic ultrasound, and MRI with each technique providing different clinical information:

  • X-ray – can only see bones and joints.   Therefore,  useful to rule out any osteoarthritis,  fractures, and dislocations.
  • Ultrasound – can be used for muscles and tendons.  Therefore,  useful for confirmation of tendinitis and bursitis including its’ severity such as tears.
  • MRI – provides high definition imaging for muscles and tendons especially if surgical option is to be considered.


Grade I

  • There is no significant structural damage
  • Microscopic inflammation and swelling
  • Commonly referred as “tendinitis”

Grade II

  • Partial Tear
  • There is structural damage but two ends of tendon are not completely severed
  • Grade II tears represent a wide spectrum ranging from minor structural tear to anything up to and short of a complete tear.

Grade III

  • Complete Tear
  • Two ends of tendon are not touching.   There is complete severance.