Psoas minor
Psoas minor · lesser psoas · psoas minor muscle
The psoas minor is a thin, long, slender muscle that lies just in front of the psoas major. Not everyone has it: it is present in only around half of people. It is small enough that its presence or absence makes little difference in daily life, but it is a muscle that comes up when examining the lower back and the front of the pelvis.
Where is it, and what does it do?
The psoas minor begins deep in the back of the abdomen, on the front of the lumbar vertebrae. It originates from the vertebral bodies around the 12th thoracic and 1st lumbar vertebrae and the disc between them, continues into a long, slender tendon, and attaches to a bony ridge near the pubis at the front of the pelvis and to the fascia covering the iliacus. As “minor” in its name suggests, it is much smaller than its neighbor, the psoas major, and lies over its front surface. The psoas major and iliacus together form the iliopsoas, and the psoas minor is described as a small helper to this muscle.
As mentioned above, some people have it and others do not. The numbers vary somewhat between studies, but it is found in roughly half of people. Some people have it on only one side. Its absence does not cause problems with walking or bending the lower back, because the iliopsoas and abdominal muscles can do those jobs adequately.
It has two main functions.
- It bends the lumbar spine slightly forward. As an assistant to the psoas major, it pulls on the front of the lower back and provides very weak assistance in bending the trunk forward.
- It pulls on the fascia at the front of the pelvis. Its tendon attaches to the fascia lining the inside of the pelvis, so when it contracts, it makes that fascia slightly taut.
Rather than a muscle that generates much force, it is more like a thin cord connecting the lower back and pelvis.
How it may feel in everyday life
It is rare to feel aching specifically in the psoas minor alone. A pulling sensation at the front of the lower back and above the groin when standing up after sitting for a long time usually comes from shortening of both the psoas major and iliacus. The psoas minor lies among these muscles, so it can contribute to a shared feeling of stiffness. It is difficult to feel directly by hand because it is deep, must be reached through the abdomen, and overlaps with the psoas major.
In Integrative Manual Therapy (IMT), the psoas minor is presented as one of the muscles that push the lumbar spine forward. Weiselfish-Giammatteo’s textbook describes it as belonging to the group that pushes the lumbar spine forward during the propulsion phase of walking, together with muscles such as the psoas major, iliacus, quadratus lumborum, and abdominal obliques. Integrative Manual Therapy views these muscles at the front of the lower back not in isolation, but as links in a chain involved in walking. This leads to an approach that considers the condition of the muscles at the front, rather than looking only at the back of the lumbar spine when the lower back feels stiff or achy.
Ways to care for it
The psoas minor is not a muscle you care for in isolation, so it is easier to think in terms of looking after its neighboring muscles as well.
- Get up after sitting for a long time. While you sit, the muscles at the front of the lower back stiffen in a shortened position. Get up about once an hour to walk, or stand and straighten your lower back.
- Stretch the front of the hip. In a kneeling lunge position with one knee on the floor, gently shifting the pelvis forward stretches the iliopsoas region. Keep your abdominal muscles engaged so your lower back does not arch, and move slowly.
- Do not arch your lower back excessively. Bending your lower back far backward in an attempt to stretch can actually cause discomfort. Remember that the area being stretched is the front of the pelvis.
- Try breathing deeply. The diaphragm and the muscles at the front of the lower back are closely connected, so when your abdomen rises and falls gently with abdominal breathing, the front of the lower back also relaxes.
- Do not press forcefully deep into the abdomen. The intestines and major blood vessels are close to this area. Rather than pressing hard yourself, leave it to a professional or use posture and movement to ease the tension.
If pain at the front of the lower back or in the groin persists, numbness or tingling spreads into the leg, or other symptoms such as fever or weight loss occur alongside it, it is a good idea to have your condition assessed.