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    Related Topics

    From Musculoskeletal System

    Brachioradialis
    Muscle responsible for forearm flexion.
    Skull
    Bony structure of the head that encases the brain.
    Cervical Vertebrae (C1 - C7)
    Vertebrae in the neck region (C1-C7).
    Ribs (12 Pairs)
    12 pairs of bones that form the sides of the thoracic cage.
    Thoracic Vertebrae (T1 - T12)
    Vertebrae in the upper and mid-back (T1-T12).
    Maxillae
    Upper jaw bones that house the teeth and form part of the orbit.
    Hamstrings
    Biceps Femoris, Semitendinosus, Semimembranosus.
    Acromioclavicular Joint
    The acromioclavicular joint connects the clavicle and scapula at the top of the shoulder, enabling smooth scapular motion and stability during arm movements.
    Lumbar Vertebrae (L1 - L5)
    Vertebrae in the lower back (L1-L5).
    Sphenoid Bone
    Bone forming part of the base of the skull and sides of the orbits.
    Radius
    Forearm bone on the thumb side.
    Parietal Bones
    Bones forming the sides and roof of the skull.
    Fibula
    Smaller bone in the lower leg, located alongside the tibia.
    Biceps Brachii
    Muscle responsible for elbow flexion.
    Acetabulum
    The acetabulum is the pelvic socket that connects with the femoral head to form the hip joint, vital for stability, movement, and weight-bearing.
    Occipital Bone
    Bone forming the back and base of the skull.
    Mandible
    Lower jawbone that houses the teeth.
    Ilium
    Uppermost and largest part of the hip bone.
    Gliding (Plane) Joints
    e.g., between carpals
    Anterior Scalene Muscle
    The anterior scalene muscle is a deep neck muscle that elevates the first rib during inspiration and aids in neck flexion and stability, located between key neurovascular structures.
    Abductor Digiti Minimi Muscle
    The abductor digiti minimi muscle is a hypothenar muscle that abducts and flexes the little finger, aiding grip and precision in hand movements.
    Thoracic Cage
    Ribs and sternum forming the protective cage for the heart and lungs.
    Ellipsoidal (Condyloid) Joints
    e.g., wrist
    Temporal Bones
    Bones forming the lower sides of the skull and housing the ears.
    Scapula
    Shoulder blade providing attachment for muscles of the upper limb.

    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? The ischium is the part of the pelvis you sit on.