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    From Musculoskeletal System

    Ilium
    Uppermost and largest part of the hip bone.
    Cervical Vertebrae (C1 - C7)
    Vertebrae in the neck region (C1-C7).
    Flexor Tendons
    Tendons that help flex the fingers and toes.
    Medial Collateral Ligament (MCL)
    Knee ligament that stabilizes the inner knee.
    Metatarsals (5 bones)
    5 bones forming the mid-foot.
    Obliques (External and Internal)
    Muscles responsible for torso rotation.
    Synchondroses
    Cartilaginous joints where bones are connected by hyaline cartilage.
    Gluteus Maximus
    Largest muscle in the buttocks responsible for hip extension.
    Tibia
    Shin bone, the larger bone in the lower leg.
    Levator Ani
    Pelvic floor muscle responsible for lifting the anus.
    Posterior Longitudinal Ligament
    Spinal ligament running along the back of the vertebral column.
    Lumbar Vertebrae (L1 - L5)
    Vertebrae in the lower back (L1-L5).
    Glenohumeral Ligaments
    Shoulder ligaments that stabilize the shoulder joint.
    Thoracic Vertebrae (T1 - T12)
    Vertebrae in the upper and mid-back (T1-T12).
    Femur
    Thigh bone, the longest and strongest bone in the body.
    Radius
    Forearm bone on the thumb side.
    Parietal Bones
    Bones forming the sides and roof of the skull.
    Ball-and-Socket Joints
    e.g., shoulder, hip
    Sternocleidomastoid
    Muscle that rotates and flexes the neck.
    Saddle Joints
    e.g., thumb joint
    Zygomatic Bones
    Cheekbones that form part of the orbit.
    Sphenoid Bone
    Bone forming part of the base of the skull and sides of the orbits.
    Carpals (8 bones)
    8 wrist bones.
    Pectoralis Major
    Chest muscle responsible for shoulder movement.
    Soleus
    Calf muscle responsible for plantarflexion of the foot.

    Extensor Tendons

    Reviewed by our medical team

    Tendons that help extend the fingers and toes.

    1. Overview

    The extensor tendons are strong, fibrous structures that connect the extensor muscles of the forearm and leg to the bones of the hand, fingers, and foot. They transmit the force generated by these muscles to extend the joints, particularly in the fingers, wrist, toes, and ankle. Extensor tendons are essential for performing actions such as releasing a grip, straightening fingers and toes, and maintaining upright posture during movement. Due to their superficial position, especially in the hand and foot, they are susceptible to injury.

    2. Location

    Extensor tendons are found in both the upper and lower limbs, typically on the dorsal (posterior) side:

    • Upper limb:

      • Extend from the lateral epicondyle of the humerus down the dorsal aspect of the wrist and into the fingers.

      • Pass through six dorsal compartments under the extensor retinaculum at the wrist.

    • Lower limb:

      • Originate from muscles of the anterior compartment of the leg and extend over the ankle to insert on the toes.

      • Pass beneath the superior and inferior extensor retinacula of the foot.

    3. Structure

    Extensor tendons are composed of dense regular connective tissue primarily made of type I collagen fibers aligned in parallel:

    • Sheathed tendons: Enclosed within synovial sheaths that reduce friction during motion, especially at the wrist and ankle.

    • Extensor mechanism (hand): Complex network over the dorsum of the fingers including the central slip, lateral bands, and terminal extensor tendon.

    • Retinacula: Thickened bands (extensor retinaculum at wrist; superior/inferior extensor retinacula at ankle) that secure tendons and prevent bowstringing.

    • Extensor hood (dorsal digital expansion): Flattened tendinous expansion that assists in coordinated finger extension by interconnecting intrinsic hand muscles.

    4. Function

    Extensor tendons transmit muscle contractions that allow the extension of joints:

    • Wrist extension: Via extensor carpi radialis longus/brevis and extensor carpi ulnaris tendons.

    • Finger extension: Controlled by extensor digitorum, extensor indicis, and extensor digiti minimi tendons.

    • Thumb extension: Enabled by extensor pollicis longus and extensor pollicis brevis tendons.

    • Toe extension: Performed by tendons of extensor hallucis longus and extensor digitorum longus in the foot.

    These actions are essential for releasing objects, walking, balancing, and fine motor activities.

    5. Physiological role(s)

    Extensor tendons contribute to a variety of physiological and functional processes:

    • Hand and foot control: Enable complex movement and fine control in the digits for tasks like writing, typing, or balancing during locomotion.

    • Posture and gait: Assist in dorsiflexion of the foot and toe extension to prevent tripping during walking.

    • Tension modulation: Distribute muscle force evenly across joints through interconnected tendon networks.

    • Proprioception: Contain mechanoreceptors that help the brain sense limb position and motion.

    6. Clinical Significance

    Extensor tendons are frequently involved in injuries, degenerative conditions, and surgical procedures:

    • Extensor tendon lacerations:

      • Commonly occur due to trauma or sharp injuries, especially on the dorsum of the hand or foot; require surgical repair if completely ruptured.

    • Mallet finger:

      • Caused by rupture or avulsion of the extensor tendon at the distal phalanx; results in inability to actively extend the fingertip.

    • Lateral epicondylitis (tennis elbow):

      • Overuse condition involving microtears in the extensor carpi radialis brevis tendon; causes lateral elbow pain.

    • Extensor tendon subluxation or dislocation:

      • Usually occurs in the hand due to damage to retinacula or sagittal bands.

    • Degenerative tendinopathies:

      • Repetitive stress and aging can lead to chronic extensor tendon inflammation, thickening, or rupture, particularly in rheumatoid arthritis.

    • Surgical relevance:

      • Common site for tendon transfers, grafts, or repair after trauma; requires careful management to restore balanced finger or foot function.

    Did you know? The knee is the largest joint in the body.