Pelvis & lower limb
Pubic symphysis
The joint where the two hip bones meet in front. It is a secondary cartilaginous joint (a symphysis): the two symphyseal surfaces are covered with hyaline cartilage and joined by a fibrocartilaginous interpubic disc. It allows only slight movement and completes the bony pelvic ring at the front.
- Structural
- Cartilaginous joint, secondary type
- Functional
- Amphiarthrosis
- Synovial type
- Not synovial
- Axes
- —
Tap a bone or ligament on the model, or choose one from the list. Hide the capsule to see what lies inside it.
3D model: Z-Anatomy (CC BY-SA 4.0), derived from BodyParts3D © DBCLS (CC BY-SA 2.1 JP). Adapted by PharmaWallah. Credits & licence
Structures
Choose one to highlight it. Grey dots are taught here but not modelled.
Bones
Special structures
Ligaments
Identification
Location: In the midline at the front of the pelvis, between the bodies of the right and left pubic bones, just above the external genitalia.
Bones taking part
Articulating surfaces
- The oval symphyseal surface on the medial side of the body of each pubis.
- Each symphyseal surface is covered with a thin layer of hyaline cartilage, and the two cartilage layers are joined by the interpubic disc of fibrocartilage.
Classification & structure
- Structural
- Cartilaginous joint, secondary type (symphysis): hyaline cartilage on each bone surface, united by a fibrocartilaginous disc.
- Functional
- Amphiarthrosis (slightly movable).
Ligaments & supporting structures
| Structure | Attachments / position | Role |
|---|---|---|
| Interpubic disc | Fibrocartilage lying between and bound to the hyaline cartilage covering the two symphyseal surfaces; it is usually thicker in females. A small slit-like space may appear inside it, but this is not a synovial cavity. | Unites the two pubic bones while allowing slight compression, separation and shear; it absorbs and spreads forces passing across the front of the pelvic ring. |
| Hyaline cartilage of the symphyseal surfaces | A thin layer covering the symphyseal surface of each pubic body. | Bonds the bone to the interpubic disc; the presence of hyaline cartilage plus a fibrocartilage disc is what makes this a secondary (not primary) cartilaginous joint. |
| Superior pubic ligament | Connects the superior aspects of the two pubic bodies and the interpubic disc, extending laterally as far as the pubic tubercles. | Reinforces the joint from above. |
| Inferior (arcuate) pubic ligament | Arches across the inferior aspect of the joint between the two pubic bones, blending with the disc; it rounds off the apex of the pubic arch (subpubic angle). | Reinforces the joint from below and is regarded as its strongest ligament. |
Movements
Slight movement only
No true active movement. The joint allows a little compression, separation, shear and twisting between the two pubic bones as forces from the lower limbs pass around the pelvic ring, for example when standing on one leg or walking. The movement increases slightly in late pregnancy when the ligaments soften.
Not at this joint
- It is not a synovial joint, so it has none of the angular movements (flexion, extension, abduction, rotation) of the hip.
- Movements of the thigh at the hip are not produced here, although adductor and abdominal muscles attach close to the joint.
Function
- Completes the pelvic ring anteriorly, linking the two hip bones so the pelvis acts as one strong ring.
- Standing: helps resist the hip bones being spread apart as body weight passes through the sacroiliac joints and down to the femora.
- Walking: absorbs and spreads the alternating forces from each lower limb across the front of the pelvis.
- Balance: its stability gives a firm base for muscles of the abdominal wall and medial thigh that attach near it.
- Childbirth: slight widening in late pregnancy helps the pelvic outlet accommodate the baby.
Stability vs mobility: Built for stability with very little mobility. The fibrocartilaginous disc firmly binds the bones, reinforced by the superior and inferior pubic ligaments. The lack of a joint cavity and synovial membrane is why it cannot move freely.
Clinical correlations
- In late pregnancy hormonal softening of the pelvic ligaments allows the symphysis to widen slightly; this can cause pubic pain (symphysis pubis dysfunction).
- Rarely, the symphysis may separate during childbirth.
- High-energy pelvic injuries can disrupt the symphysis ('open-book' injury), widening the pelvic ring.
- The pubic symphysis and pubic crest are palpable landmarks used in clinical examination.
What examiners look for
- Class: secondary cartilaginous joint (symphysis) — not synovial, not fibrous.
- Explain 'secondary': hyaline cartilage on each bone + fibrocartilaginous disc between.
- Explain 'not synovial': no fibrous capsule lined with synovial membrane, no synovial fluid; any slit inside the disc is not a synovial cavity.
- Ligaments: superior pubic and inferior (arcuate) pubic.
- Functional class: amphiarthrosis.
- Contrast with primary cartilaginous joints (hyaline cartilage only, e.g. an epiphyseal growth plate).
Common mistakes
- Calling it a synovial joint — it has no synovial membrane or synovial cavity.
- Calling it a primary cartilaginous joint — it has a fibrocartilage disc, so it is secondary.
- Calling it a fibrous joint or suture.
- Saying it allows no movement at all — it allows slight movement (amphiarthrosis).
- Writing that the pubic symphysis joins the ischium — it joins the bodies of the two pubic bones.
Viva questions
Classify the pubic symphysis.Show answer
A secondary cartilaginous joint (symphysis), functionally an amphiarthrosis.
Why is it called a secondary cartilaginous joint?Show answer
Each bone surface is covered with hyaline cartilage, and the two are joined by a fibrocartilaginous disc; a primary cartilaginous joint has hyaline cartilage only.
Why is it not a synovial joint, even though a small space may be seen inside the disc?Show answer
It has no synovial membrane, no synovial fluid and no articular capsule of the synovial type; the slit within the disc is not a synovial cavity.
Name the ligaments of the pubic symphysis.Show answer
The superior pubic ligament and the inferior (arcuate) pubic ligament.
What does the inferior pubic ligament form?Show answer
It rounds off the apex of the pubic arch (the subpubic angle).
What happens to the joint in pregnancy?Show answer
Its ligaments soften under hormonal influence, allowing slight widening, which helps childbirth but can cause pubic pain.
Name another example of a secondary cartilaginous joint.Show answer
The joint between two vertebral bodies with an intervertebral disc.
Revision notes
- Midline, front of pelvis, between bodies of the two pubic bones.
- Secondary cartilaginous joint = symphysis = amphiarthrosis.
- Hyaline cartilage on each symphyseal surface + fibrocartilaginous interpubic disc.
- Ligaments: superior pubic and inferior (arcuate) pubic.
- Not synovial: no capsule of synovial type, no synovial membrane or fluid.
- Slight movement; widens slightly in late pregnancy.
Related joints
References
- Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. 5th ed. Philadelphia: Elsevier; 2023.
- Moore KL, Dalley AF, Agur AMR. Moore's Clinically Oriented Anatomy. 9th ed. Philadelphia: Wolters Kluwer; 2023.
- Federative International Programme for Anatomical Terminology (FIPAT). Terminologia Anatomica. 2nd ed. FIPAT.library.dal.ca; 2019. fipat.library.dal.ca/TA2
- Kervyn G, Zielinski M, Vinent L, et al. Z-Anatomy: the libre 3D atlas of anatomy. Models derived from BodyParts3D, The Database Center for Life Science (CC BY-SA 2.1 JP). CC BY-SA 4.0. www.z-anatomy.com/
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