Psoas Minor

Origin, Insertion, Action & Nerve

Attachments explained

The Psoas Minor is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.

Action & function

When the Psoas Minor contracts, it produces the following movement: Weakly flexes the trunk (lumbar vertebral column).

As part of the Gluteal & Hip group of the Lower Limb, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.

Nerve supply & clinical relevance

The Psoas Minor receives its nerve supply from the Anterior ramus of L1. This nerve carries fibres from spinal segment(s) L1.

Because a muscle can only contract when its nerve is intact, injury to the Anterior ramus of L1 or to its spinal roots (L1) can weaken or paralyse the Psoas Minor, impairing the movements it normally produces (weakly flexes the trunk (lumbar vertebral column)). This is why knowing the innervation is central to localising nerve lesions in clinical practice.

How to study the Psoas Minor (the OIANS method)

OIANS stands for Origin, Insertion, Action and Nerve, the four facts that uniquely define every skeletal muscle. To learn the Psoas Minor, work through them in order: picture its origin, trace the muscle to its insertion, reason out the action that shortening between those two points must create, then add the nerve that drives it.

Most students remember the Psoas Minor fastest by linking its action back to its attachments rather than memorising each fact in isolation. Once the origin and insertion make sense, the action usually follows logically.

Psoas Minor quick facts

Region

Lower Limb

Group

Gluteal & Hip

Origin

Lateral surfaces of the bodies of T12 and L1 and the intervening intervertebral disc

Insertion

Pectineal line of the pubis and iliopubic (iliopectineal) eminence

Action

Weakly flexes the trunk (lumbar vertebral column)

Nerve

Anterior ramus of L1

Spinal roots

L1

Frequently asked questions

Related muscles