Flexion is a term used in anatomical terminology that refers to a movement that decreases the angle between two bones at a joint. For example, your elbow joint flexes when you bring your hand closer to the shoulder. Flexion is typically instigated by muscle contraction. A muscle that flexes a joint is called a flexor. In anatomy, flexion (from the Latin verb flectere, to bend) is a joint movement that decreases the angle between the bones that converge at the joint.
The iliacus and nearby muscles
The hip flexors are (in descending order of importance to the action of flexing the hip joint):
- Collectively known as the iliopsoas or inner hip muscles:
Without the iliopsoas muscles, flexion in sitting position is not possible across the horizontal plane.
- This article uses anatomical terminology; for an overview, see anatomical terminology.