Deltoid Muscle Strain

The deltoid muscle is a large and powerful muscle in the shoulder joint. During our everyday tasks the deltoid muscle does most of the work for your shoulder movements. Along with the rotator cuff it helps stabilize your shoulder joint from dislocation.

Deltoid strain is a common injury with shoulder muscles.

The shoulder can be overextended with some movements such as throwing or lifting too much. Long periods of over-use and abuse to the shoulder muscles can easily produce trigger points pain that can be felt as a deep pain in the shoulder. A fall or sudden injury can cause dislocation of the shoulder causing damage to the muscle.

The affected shoulder may have signs and symptoms as:

  • Swelling, bruising to the area (from damaged to small blood vessels under the skin) or redness
  • Pain and soreness when at rest
  • Stiffness in the muscle
  • Limited range of movement or unable to use the muscle (shoulder/arm) at all.

More serve cases may experience even more range of motion, weakness and muscle loss (atrophy), the outer end of the scapula to which the collarbone is attached to the acromion bone can be seen painly as a bump on the shoulder.

There are three grades to a deltoid muscle strain.


  • Grade 1 – a minor tear of the muscle (10% of the muscle fibers). You may be able to continue your activity because the pain is minor twinge in your shoulder. The shoulder muscle feels achy and tightness for two to five days after the injury, recovery for healing is 7 to 10 days.
  • Grade 2 – partial tearing of the deltoid muscle (90% of the muscle fibers). You will feel sharp pain and minor to moderate swelling of your shoulder. Lifting your arm to the front, side or back and carrying a small load (carrying a bag of groceries) will cause pain and may be difficult to do. The shoulder muscle feels achy and tightness for a least a week after the injury, recovery for healing within about 4 to 6 weeks
  • Grade 3 – complete tearing of over 90% of the deltoid muscle or rupture. This is the most painful of all the grades of shoulder deltoid pain, causing immediate severe pain, considerable bruising and swelling in the shoulder. A slight flex of the muscle might produce a bulge. You may not able to use your arm for daily activities, achy, tightness for about 30 to 35 days, recovery for healing within about three to four months.


Depending on the severity of the deltoid injury the effective treatment will concentrate on:

  • Stabilising the shoulder to prevent further injury and allow recovery to occur.
  • A specific physical therapy program comprised of strengthening and mobilisation exercises to prevent frozen shoulder and re-strengthen the damage muscle.
  • ESWT Shockwave therapy, which has been shown increase muscle healing rates by rebuilding soft tissue, is used to dramatically reduce recovery time.
  • A progressive increase in mobility and intensity of the prescribed rehabilitation exercises without causing re-injury combined with EWST Shockwave therapy, is the most successful method to allow full recovery.

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