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    Related Topics

    From Musculoskeletal System

    Clavicle
    Collarbone connecting the arm to the body.
    Biceps Brachii
    Muscle responsible for elbow flexion.
    Coccyx
    Tailbone, the remnant of the tail in humans.
    Ischium
    Part of the pelvis that supports weight while sitting.
    Lacrimal Bones
    Bones forming part of the eye socket and housing the tear ducts.
    Facial Bones
    Bones forming the structure of the face.
    Latissimus Dorsi
    Back muscle responsible for arm adduction and extension.
    Metacarpals (5 bones)
    5 bones forming the palm of the hand.
    Diaphragm
    Primary muscle for breathing.
    Ribs (12 Pairs)
    12 pairs of bones that form the sides of the thoracic cage.
    Lateral Collateral Ligament (LCL)
    Knee ligament that stabilizes the outer knee.
    Fibula
    Smaller bone in the lower leg, located alongside the tibia.
    Palatine Bones
    Bones forming part of the hard palate and nasal cavity.
    Anterior Longitudinal Ligament
    Spinal ligament running along the front of the vertebral column.
    Adductors
    Muscles that bring the thighs toward the midline.
    Phalanges (14 bones)
    14 bones forming the toes.
    Synchondroses
    Cartilaginous joints where bones are connected by hyaline cartilage.
    Iliolumbar Ligament
    Ligament connecting the ilium and lumbar vertebrae.
    Temporal Bones
    Bones forming the lower sides of the skull and housing the ears.
    Mandible
    Lower jawbone that houses the teeth.
    Pectoralis Major
    Chest muscle responsible for shoulder movement.
    Skull
    Bony structure of the head that encases the brain.
    Tibia
    Shin bone, the larger bone in the lower leg.
    Sacroiliac Ligaments
    Ligaments connecting the sacrum to the iliac bones.
    Sternum
    Breastbone located in the center of the chest.

    Pivot Joints

    Reviewed by our medical team

    e.g., atlanto-axial joint

    1. Overview

    A pivot joint, also known as a trochoid joint, is a type of synovial joint that allows rotational movement around a single axis. It functions like a mechanical axle, enabling one bone to rotate around another. Pivot joints are essential for motions such as head rotation and forearm pronation and supination. Though limited in range, they play a vital role in daily motor activities.

    2. Location

    There are two primary pivot joints in the human body:

    • Atlantoaxial joint (cervical spine): Located between the first (atlas) and second (axis) cervical vertebrae; allows head rotation side-to-side (e.g., "no" movement).

    • Proximal radioulnar joint (forearm): Located near the elbow, between the head of the radius and the radial notch of the ulna; enables pronation and supination of the forearm.

    3. Structure

    A pivot joint consists of a rounded or pointed bone that rotates within a ring formed by another bone and a ligament:

    • Bone component: One bone has a bony process (e.g., the dens of the axis or the radial head).

    • Ring or sleeve: This may be bony (e.g., atlas) or ligamentous (e.g., annular ligament of the radius).

    • Joint capsule: A fibrous capsule encloses the joint, allowing synovial fluid to lubricate and reduce friction.

    • Ligaments: Support and limit the range of motion; examples include the transverse ligament of the atlas and annular ligament in the elbow.

    4. Function

    Pivot joints allow uniaxial rotation around a central axis:

    • Rotation: The only permitted motion; no flexion, extension, abduction, or adduction.

    • Example in neck: Rotation of the head left and right via the atlantoaxial joint.

    • Example in forearm: Pronation (palm down) and supination (palm up) movements via the proximal radioulnar joint.

    5. Physiological role(s)

    Pivot joints are essential for specific physiological tasks and functional mobility:

    • Vision and awareness: The atlantoaxial pivot joint allows the head to rotate and track visual or auditory stimuli.

    • Tool manipulation: The radioulnar pivot enables rotational forearm movement, allowing gripping, turning, and writing.

    • Neuromuscular coordination: Smooth rotational movement supports coordinated motor skills in upper limb and neck.

    6. Clinical Significance

    Though small, pivot joints are subject to specific injuries and disorders:

    • Atlantoaxial instability:

      • May be congenital (e.g., Down syndrome) or acquired (e.g., rheumatoid arthritis), posing a risk for spinal cord compression.

    • Rotational subluxation:

      • Occurs when the atlas and axis misalign; can lead to torticollis or restricted head movement.

    • Radial head dislocation (nursemaid’s elbow):

      • Common in young children; results from sudden traction on the forearm causing the radial head to slip out of the annular ligament.

    • Fractures:

      • Radial head fractures can impair pronation and supination; dens fractures affect cervical rotation and may compromise neural structures.

    • Rheumatoid arthritis:

      • Chronic inflammation may erode ligaments or bones, especially in the cervical spine, destabilizing the pivot joint.

    Did you know? Sesamoid bones are bones that form within tendons, like the patella.