Upper limb
Infraspinatus
Musculus infraspinatus
- Origin
- Infraspinous fossa of the scapula
- Insertion
- Greater tubercle of the humerus (middle facet)
- Function
- External rotation of the shoulder; stabilizes the humeral head in the glenoid fossa
- Innervation
- Suprascapular nerve (C5-C6)
- Movement & chain
- Part of the rotator cuff; works together with teres minor in external rotation and with the other cuff muscles in centering the head during every arm movement.
- Palpation
- Easily felt in the infraspinous fossa below the scapular spine, especially during resisted external rotation with the elbow at 90° flexion.
- Clinical
- Common site of rotator cuff tears and tendinopathy, often together with supraspinatus; atrophy is visible as a hollow in the infraspinous fossa with prolonged suprascapular nerve palsy.
- Segmental innervation
- Suprascapular nerve, C5-C6.
- In clinical practice
- The external rotation lag sign and the resisted external rotation test with the elbow fixed against the trunk are used clinically to assess infraspinatus function and rotator cuff integrity.
- Region in the model
- Upper limb