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    Related Topics

    From Musculoskeletal System

    Achilles Tendon
    Tendon connecting the calf muscle to the heel bone.
    Anterior Longitudinal Ligament
    Spinal ligament running along the front of the vertebral column.
    Symphyses
    Cartilaginous joints where bones are connected by fibrocartilage.
    Femur
    Thigh bone, the longest and strongest bone in the body.
    Lacrimal Bones
    Bones forming part of the eye socket and housing the tear ducts.
    Sphenoid Bone
    Bone forming part of the base of the skull and sides of the orbits.
    Palatine Bones
    Bones forming part of the hard palate and nasal cavity.
    Rotator Cuff Muscles
    Supraspinatus, Infraspinatus, Teres Minor, Subscapularis.
    Scapula
    Shoulder blade providing attachment for muscles of the upper limb.
    Ellipsoidal (Condyloid) Joints
    e.g., wrist
    Carpals (8 bones)
    8 wrist bones.
    Acromioclavicular Ligament
    Ligament that connects the acromion to the clavicle.
    Ischium
    Part of the pelvis that supports weight while sitting.
    Cervical Vertebrae (C1 - C7)
    Vertebrae in the neck region (C1-C7).
    Medial Collateral Ligament (MCL)
    Knee ligament that stabilizes the inner knee.
    Humerus
    Upper arm bone connecting the shoulder to the elbow.
    Hinge Joints
    e.g., elbow, knee
    Quadriceps Tendon
    Tendon that connects the quadriceps to the patella.
    Ulna
    Forearm bone on the pinky side.
    Vomer Bone
    Bone forming the nasal septum.
    Masseter
    Muscle that elevates the mandible.
    Lateral Collateral Ligament (LCL)
    Knee ligament that stabilizes the outer knee.
    Ilium
    Uppermost and largest part of the hip bone.
    Biceps Brachii
    Muscle responsible for elbow flexion.
    Extensor Tendons
    Tendons that help extend the fingers and toes.

    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? Bones are living tissue that is constantly remodeling and repairing itself.