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MuscleShoulderintermediateDraft

InfraspinatusMusculus infraspinatus

Thick, flat rotator cuff muscle below the spine of the scapula that laterally rotates the arm and steadies the shoulder joint.

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LatinMusculus infraspinatus
Origin
  • Infraspinous fossa of the scapula
Insertion
  • Middle facet of the greater tubercle of the humerus
Action
  • Laterally (externally) rotates the arm
  • Stabilises the glenohumeral (shoulder) joint by holding the head of the humerus in the socket
NerveSuprascapular nerve (C5–C6)
NameLatin infra, 'below', and spina, 'spine' — it lies below the spine of the scapula.

Palpation

  1. Client prone with the arm resting by the side or hanging off the table edge.
  2. Find the spine of the scapula, then place your fingers flat in the broad area below it, between the medial and lateral borders.
  3. Feel a thick, dense muscle filling most of the back of the shoulder blade.
  4. Ask the client to rotate the arm outwards (turn the palm away from the body) against light resistance; feel the muscle firm up.

Landmarks: Spine of scapula · Medial border of scapula · Inferior angle of scapula

Infraspinatus is the “I” in SITS, the four rotator cuff muscles (Supraspinatus, infraspinatus, Teres minor and Subscapularis). It shares its nerve with supraspinatus and does most of the work of lateral rotation, helped by teres minor just below it.

It fills the area below the Spine of scapula and is one of the easiest cuff muscles to reach, as only a thin edge is covered by the Deltoid and lower Trapezius. Many clients report tender spots here that seem to spread into the front or side of the shoulder. Work it with circular friction and sustained compression on the flat bone underneath.

Techniques

  • Petrissage — Kneading strokes that compress, lift and squeeze the muscle away from the bone, working the tissue between the hands.
  • Circular friction — Small circles made with the finger or thumb pads that move the skin over the deeper tissue without sliding, to work a specific spot.
  • Compression — Pressing straight down into a muscle with the palm, fist or forearm, holding briefly, then releasing and moving on.
  • Effleurage — Long, gliding strokes with the whole palm that spread the medium, warm the tissue and link the other strokes together.

Works with

  • Teres minor — Narrow rotator cuff muscle along the lateral border of the scapula that laterally rotates the arm and stops the humerus riding upwards.
  • Deltoid — Thick, triangular muscle that caps the shoulder and is the main muscle for lifting the arm out to the side.
  • Supraspinatus — Rotator cuff muscle above the spine of the scapula that starts arm abduction and holds the head of the humerus in its socket.

Opposes

  • Subscapularis — Large, triangular rotator cuff muscle on the front of the scapula that medially rotates the arm and guards the front of the shoulder joint.
  • Teres major — Thick, rounded muscle from the inferior angle of the scapula to the front of the humerus that pulls the arm down, back and inwards.
  • Pectoralis major — Large, fan-shaped chest muscle that flexes, adducts and medially rotates the arm.
  • Latissimus dorsi — Broad, flat, fan-shaped muscle of the lower and middle back that extends, adducts and medially rotates the arm.

Used in routines

Sources

  1. Wikipedia: Infraspinatus muscle
  2. Wikipedia: Suprascapular nerve