When we talk about the shoulder we usually mean the deltoid. There are more important muscles around your shoulder joint than deltoid, like the rotator cuff muscles, and you should take care of them to avoid injuries.

The Deltoid muscle is the muscle forming the rounded contour of the shoulder. It is divided into three portions, anterior, lateral and posterior, with the fibers having different roles due to their orientation.


  1. The anterior fibers are involved in shoulder abduction when the shoulder is externally rotated. It also works with the subscapularis, pecs and lats to internally (medially) rotate the humerus.
  2. The posterior fibers are strongly involved in transverse extension particularly as the latissimus dorsi is very weak in strict transverse extension. The infraspinatus and teres minor, also work with the posterior deltoid as external rotators, antagonists to strong internal rotators like the pecs and lats. The posterior deltoid is also the primary shoulder hyperextensor, more so than the long head of the triceps which also assists in this function.
  3. The lateral fibers perform the shoulder abduction when it is internally rotated, and perform shoulder transverse abduction when the shoulder is externally rotated.


  1. Lateral, anterior 1/3 of the distal clavicle.
  2. Lateral boarder of the acromion.
  3. Scapular spine.


Deltoid tuberosity of the humerus.

Pain and symptoms associated with the Deltoid muscle

– Pain over the tip of the shoulder going down the upper arm
– Shoulder weakness
– Pain in the shoulder area when lifting
– Pain in the shoulder area when holding objects up and in front of the body
– Pain decreases when arm and shoulder are at rest

Pain around the shoulder area caused by the deltoids muscles will subside when resting. If the pain in the deltoid area is continuous even at rest, chances are the source of the pain is being caused by other muscles in the neck, shoulder, upper back, and/or chest.

Activities that cause deltoid pain and symptoms

– Swimming
– Skiing
– Weight-lifting
– Throwing a ball; baseball, softball, football
– Holding heavy tools up
– Picking up and carrying children
– Typing when the keyboard is set up too high

The Teres major is a medial rotator and adductor of the humerus and assists the latissimus dorsi in drawing the previously raised humerus downward and backward (extension, but not hyperextension). It also helps stabilize the humeral head in the glenoid cavity. It is only functional when the Rhomboids fix the scapula. This muscle mainly helps latissimus dorsi.


Inferior, lateral margin of the scapula.


Crest of lesser tubercle (just medial to the insertion of latissimus dorsi)

Pain and symptoms associated with the Teres Major muscle

– Pain in the back of the upper arm when reaching forward and up
– Sharp pain in the back of the shoulder with aching sensation in the upper arm when resting elbows on a table.
– Pain in the back of the arm that skips the elbow and continues down to the back of the forearm.

Activities that cause teres major muscle pain and symptoms

– Rowing
– Throwing or pitching a ball
– Swimming
– Chopping wood
– Driving
– Exercise that requires pulling up (chin-up) or pushing down (push-ups) with the arms, or reaching forward or overhead repetitiously

The Supraspinatus muscle is one of the four muscles which make up the rotator cuff. Its main function is to stabilize the upper arm by holding the head of the humerus in position. It is important in throwing motions to control any forward motion of the head of the humerus. Contraction of the supraspinatus muscle leads to the abduction of the arm at the shoulder joint. It is the main agonist muscle for this movement during the first 10-15 degrees of its arc. Beyond 30 degrees, the deltoid muscle becomes increasingly more effective at abducting the arm and becomes the main propagator of this action.


  1. Supraspinous fossa.
  2. Muscle fascia.


Uppermost of three facets of the greater tubercle of the humerus.

Pain and symptoms associated with the Supraspinatus muscle

– Deep ache over the outside of the shoulder area which continues during rest
– Pain down the outside of the arm, occasionally extending down into the wrist
– Can cause clicking or popping in the shoulder joint
– Concentrated pain toward the outside of the elbow
– Pain when lifting the arm overhead
– Difficulty and shoulder pain while shaving the face or combing hair

Activities that cause supraspinatus muscle pain and symptoms

– Carrying heavy objects with the arm hanging down ie. suitcase, a bucket of paint, etc.
– Working with arms outstretched in front of the body and /or overhead (painting, working at the computer, driving for long periods)
– Tennis
– Golf

The Infraspinatus muscle is another of the four rotator cuff muscles crossing the shoulder joint and is commonly injured. It is the main external rotator of the shoulder joint. When the arm is fixed, it abducts the inferior angle of the scapula. Its synergists are teres minor and the deltoid. The infraspinatus and teres minor rotate the head of the humerus outward (external, or lateral, rotation); they also assist in carrying the arm backward. Also, reinforces the capsule of the shoulder joint.


  1. Infraspinous fossa.
  2. Muscle fascia.


The middle facet of greater tubercle of the humerus.

Pain and symptoms associated with the Infraspinatus muscle

– Pain deep in the front of the shoulder
– Pain going down the front and outside of the arm, sometimes going down into the hand
– Pain going up the back of the neck to the base of the skull
– Pain in the upper back at the inside edge of the shoulder blade
– Weakness and stiffness in the shoulder and arm
– Difficulty reaching the arm behind the body and reaching into a back hip pocket

Activities that cause infraspinatus pain and symptoms

– Keeping the arms overhead for extended periods of time
– Painting overhead
– Keeping the arms extended in front of the body for extended periods of time
– Driving with hands on top of the steering wheel
– Keyboarding and using the mouse on the computer
– Swimmers
– Sports throwing a ball or swinging at a ball
– Tennis
– Baseball
– Football

The subscapularis rotates the head of the humerus medially (internal rotation); when the arm is raised, it draws the humerus forward and downward. It is a powerful defense to the front of the shoulder-joint, preventing displacement of the head of the humerus.


Subscapular fossa.


Lesser tubercle of the humerus.

Pain and symptoms associated with the Subscapularis muscle

– Severe pain deep in the back of the shoulder
– Pain in the back of the upper arm
– Pain over the shoulder blade area
– Pain can extend down the back of the arm
– Persistent aching in the wrist with extreme tenderness in the back of the wrist
– Occasionally an extremely tender spot on the front of the shoulder

Activities that cause subscapularis pain and symptoms

– Pitching a baseball
– Tennis
– Swimming
– Tossing heavy objects
– Playing the violin, guitar, banjo
– Falling and landing on your side
– Sleeping on one side
– Immobilization of the arm for long periods (casted arm)

The Teres minor is a narrow, elongated muscle of the rotator cuff.

The Teres minor and the infraspinatus attach to the head of the humerus; they help hold the humeral head in the glenoid cavity of the scapula. They work in tandem with the posterior deltoid to externally (laterally) rotate the humerus, as well as perform transverse abduction, extension, and transverse extension.


The middle half of the scapula’s lateral margin.


Lowest of three facets of the greater tubercle of the humerus.

Pain and symptoms associated with the Teres Minor muscle

– Pain toward the back of the upper arm
– Numbness or tingling without pain or aches in the fourth and fifth fingers

Activities that cause teres minor pain and symptoms

– Bringing the arm back with force
– Pitching a baseball
– Rowing, Kayaking
– Holding arms above head for extended periods
– Holding arms out in front of the body for extended periods of time
– Bracing your arms either in front of the body to avoid a fall or overhead impact (something falling from above)

There are two types of rotator cuff injuries:

  1. Acute tears occur as a result of a sudden movement. This might include throwing a powerful pitch, holding a fast moving rope during water sports, falling over onto an outstretched hand at speed, or making a sudden thrust with the paddle in kayaking.
  2. A chronic tear develops over a period of time. They usually occur at or near the tendon, as a result of the tendon rubbing against the underlying bone.

Rotator cuff tear

Please, be careful :)

21 thoughts on “Shoulder”

  1. Thanks for the post that I needed to see….I had a torn rotator cuff years ago from lifting a heavy rock…I refused surgery and let it heal naturally, 6 to 8 weeks, however I was told it will be weak and probably be subject to arthritis in my later years…well my later years are here and the first part of my body that hurts when I work out is my rotator cuff on my right arm…I try to push through the pain but sometimes I have to just give in and either stop or lighten the weight….any advice??? My thought is lighten the weights before I reinjure my muscle and back off when it starts to ache and have pain…??? I hate ice, but I am guessing it would be better than heat??? kat

  2. You´re welcome Kat! Thank you for sharing your experience. My first advice is: avoid all kind of press exercises (chest, shoulder…) for a long, long time. I will probably force you to do only preacher curl bench for your biceps. As you see, we try to keep the shoulders fixed, so the rotator cuff don´t work (too much at least). With this couple of things, you can adapt your workout to your little problem. Now, in order to rehab and improve these little bast*** First, avoid mistakes (VERY serious):
    With these tips in mind, specific exercises:
    If you feel pain, STOP, there is always another day! I´m not a fan of ice or heat, but simply rest as necessary. If you have more questions, please, will be a pleasure. David :)

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