Lateral triangular space
The lateral triangular space, also called the triangular interval or lower triangular space 1 or triceps hiatus, is a space connecting the axilla to the posterior compartment of the arm. It should not be confused with the similarly named medial (upper) triangular space.
It is a downwards pointing triangle with a base superiorly and apex inferiorly.
- long head of triceps brachii muscle (medial margin)
- teres major muscle (superior margin)
- humerus (lateral margin)