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    Related Topics

    From Musculoskeletal System

    Iliolumbar Ligament
    Ligament connecting the ilium and lumbar vertebrae.
    Sutures (in the skull)
    Fibrous joints between skull bones.
    Coracoacromial Ligament
    Ligament that connects the acromion to the coracoid process.
    Quadriceps Tendon
    Tendon that connects the quadriceps to the patella.
    Lateral Collateral Ligament (LCL)
    Knee ligament that stabilizes the outer knee.
    Posterior Cruciate Ligament (PCL)
    Knee ligament that stabilizes the joint.
    Saddle Joints
    e.g., thumb joint
    Hinge Joints
    e.g., elbow, knee
    Coccygeus
    Pelvic floor muscle supporting the coccyx.
    Metatarsals (5 bones)
    5 bones forming the mid-foot.
    Rotator Cuff Tendons
    Tendons of the rotator cuff muscles.
    Obliques (External and Internal)
    Muscles responsible for torso rotation.
    Sesamoid Bones
    e.g., patella, some found in hands/feet.
    Flexor and Extensor Groups
    Muscles responsible for flexing and extending the hand and wrist.
    Latissimus Dorsi
    Back muscle responsible for arm adduction and extension.
    Sacroiliac Ligaments
    Ligaments connecting the sacrum to the iliac bones.
    Phalanges (14 bones)
    14 bones forming the toes.
    Wormian Bones
    Sutural bones in the skull.
    Quadriceps
    Rectus Femoris, Vastus Medialis, Vastus Lateralis, Vastus Intermedius.
    Biceps Tendon
    Tendon that attaches the biceps muscle to the bone.
    Tarsals (7 bones)
    7 ankle bones.
    Coccyx
    Tailbone, the remnant of the tail in humans.
    Humerus
    Upper arm bone connecting the shoulder to the elbow.
    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.
    Achilles Tendon
    Tendon connecting the calf muscle to the heel bone.

    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 metatarsals are the bones in the feet that connect to the toes.