Shoulder Instability

How does shoulder instability occur?

The shoulder is a ball and socket joint. It is the most mobile joint in your body.

This greater range of motion, however, can predispose you to shoulder instability. Shoulder instability occurs when the head, or ball, of the upper arm bone is forced out of the shoulder socket. This can happen as a result of a sudden injury or from repetitive overhead activity related to sport (e.g. volleyball, tennis) or work. Once a shoulder has dislocated, it is vulnerable to repeat episodes. In some patients, the shoulder can become unstable without a history of injury or repetitive strain. These patients have naturally loose ligaments throughout the body and may say they are “double-jointed”. Often, their shoulder is unstable in more than one direction.


Chronic shoulder instability is often first treated with non-surgical options. If these options do not relieve the pain and instability, surgery may be needed. It often takes several months of non-surgical treatment before you can tell how well it is working. Non-surgical treatment typically includes:

1) Activity modification

You must stay in a protected range of motion where your shoulder feels stable. Avoid activities, positions and “trick movements” that promote instability. This depends on the direction of instability.

I. Anterior instability (most common)

  • Avoid lifting your arm out to the side combined with rotating your shoulder outward.
    • E.g. throwing overhand, overhand serves in tennis or volleyball, lying on your back with
      your hands behind your head or sleeping on your stomach with your arm overhead.

      Shoulder Abduction + External Rotation

      Abduction + External Rotation

  • Avoid lifting your arm out to the side and reaching behind your body.
    • E.g. reaching into the back seat of your vehicle.
  • Avoid exercises that move your elbows or hands behind the plane of the body or in a position of abduction + external rotation (see image above).
    • E.g. bench press, overhead military press, pec flies, lat pull-downs, tricep dips, wide grip chin-ups, horizontal row, reverse plank, or holding or pulling down a bar behind your head.
  • Avoid hanging exercises or any exercise that causes a traction effect on the shoulder e.g. chin-ups.

II. Posterior instability

  • Avoid the combined motion of lifting your arm forward, across your body and internal rotation
    (thumb rotated inward or down).

    Flexion horizontal adduction internal rotation

    Flexion + horizontal adduction + internal rotation

  • You are safer reaching overhead with your arms wider apart and out to the side vs. in front of
    you (flexion).
  • Avoid reaching across the front of your body (horizontal adduction).
    • E.g. shaving or putting on deodorant under your opposite arm or reaching across to put
      on a seatbelt.
  • Avoid exercises that involve weight-bearing or loading the shoulder with the hand in front of
    the shoulder.

    • E.g. planking, push-ups (shoulder width or narrower) or bench press.
  • Avoid hanging exercises or any exercise that can cause a traction effect on the shoulder such
    as pull-ups.

2) Physical Therapy

Your therapist will design a home-based exercise program for your shoulder. Your rehabilitation program should include:

  • Education to prevent recurrence i.e. activity modification.
  • Posture re-education, core stabilization and strengthening.
  • Motor control training of specific muscles during functional activities (rotator cuff muscles, scapular stabilizers).
  • Strengthening of the shoulder girdle, in particular the deltoid, rotator cuff muscles and scapular stabilizers.
  • Stretching in particular posterior shoulder structures, pectoralis major and minor and any other muscles with flexibility impairments (dependent on direction of instability).
  • Manual therapy, as needed, targeting impairments of mobility in the acromioclavicular, sternoclavicular joints and cervical and thoracic spine.

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