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    From Musculoskeletal System

    Coracoacromial Ligament
    Ligament that connects the acromion to the coracoid process.
    Skull
    Bony structure of the head that encases the brain.
    Humerus
    Upper arm bone connecting the shoulder to the elbow.
    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.
    Deltoid
    Shoulder muscle responsible for arm abduction.
    Cervical Vertebrae (C1 - C7)
    Vertebrae in the neck region (C1-C7).
    Patella
    Knee cap, protecting the knee joint.
    Gluteus Maximus
    Largest muscle in the buttocks responsible for hip extension.
    Ribs (12 Pairs)
    12 pairs of bones that form the sides of the thoracic cage.
    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.
    Sternum
    Breastbone located in the center of the chest.
    Obliques (External and Internal)
    Muscles responsible for torso rotation.
    Mandible
    Lower jawbone that houses the teeth.
    Maxillae
    Upper jaw bones that house the teeth and form part of the orbit.
    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.
    Gomphoses
    Fibrous joints where a peg fits into a socket (e.g., teeth in jaw).
    Adductors
    Muscles that bring the thighs toward the midline.
    Tarsals (7 bones)
    7 ankle bones.
    Scapula
    Shoulder blade providing attachment for muscles of the upper limb.
    Ball-and-Socket Joints
    e.g., shoulder, hip
    Iliolumbar Ligament
    Ligament connecting the ilium and lumbar vertebrae.
    Pivot Joints
    e.g., atlanto-axial joint
    Cranial Bones
    Bones of the skull that protect the brain.
    Sutures (in the skull)
    Fibrous joints between skull bones.

    Rotator Cuff Tendons

    Reviewed by our medical team

    Tendons of the rotator cuff muscles.

    1. Overview

    The rotator cuff tendons are the tendinous extensions of the four rotator cuff muscles—supraspinatus, infraspinatus, teres minor, and subscapularis. These tendons insert on the humeral head and work together to stabilize the glenohumeral (shoulder) joint. They form a continuous sheath over the shoulder joint capsule and play a vital role in dynamic shoulder stability and motion.

    2. Location

    The rotator cuff tendons are located around the proximal humerus and encapsulate the shoulder joint:

    • Supraspinatus tendon: Passes under the acromion and inserts on the superior facet of the greater tubercle of the humerus.

    • Infraspinatus tendon: Inserts on the middle facet of the greater tubercle.

    • Teres minor tendon: Inserts on the inferior facet of the greater tubercle.

    • Subscapularis tendon: Inserts on the lesser tubercle of the humerus (anteriorly).

    3. Structure

    Rotator cuff tendons are composed of dense regular connective tissue primarily made up of Type I collagen fibers:

    • Collagen alignment: Fibers are oriented along the direction of pull to withstand tensile loads.

    • Insertion zones: Tendons transition through four zones—tendon, unmineralized fibrocartilage, mineralized fibrocartilage, and bone—to create a strong, gradual attachment.

    • Vascular supply: Relatively poor, especially in the supraspinatus tendon (notably in the “critical zone”), which makes it prone to degeneration and tears.

    • Synovial sheath: Tendons are surrounded by a synovial layer to reduce friction during motion.

    4. Function

    The rotator cuff tendons transmit force from the muscle bellies to the humeral head and:

    • Stabilize the shoulder: Anchor the humeral head into the glenoid fossa during shoulder movement.

    • Coordinate movement: Work synergistically with deltoid and scapular muscles to guide shoulder elevation and rotation.

    • Control joint mechanics: Prevent superior migration of the humeral head during arm elevation.

    5. Physiological role(s)

    Rotator cuff tendons contribute to upper limb mechanics and coordination:

    • Enable complex motions: Facilitate overhead activities, throwing, reaching, and lifting.

    • Proprioception: Contain sensory receptors that relay information about joint position and muscle tension.

    • Load distribution: Help spread mechanical stress across the shoulder capsule and joint surfaces.

    6. Clinical Significance

    Rotator cuff tendons are prone to injury due to their anatomical location, limited vascularity, and frequent use:

    • Tendon tears:

      • Partial thickness: Damage to some tendon fibers; often seen in overhead athletes and laborers.

      • Full-thickness (complete): Complete detachment of tendon from bone, most commonly affecting the supraspinatus.

    • Tendinopathy:

      • Chronic overuse can lead to tendon degeneration, thickening, and fibrosis—often referred to as rotator cuff tendinosis.

    • Impingement syndrome:

      • Compression of the rotator cuff tendons (especially supraspinatus) beneath the acromion, leading to inflammation and pain.

    • Calcific tendinitis:

      • Calcium deposits form within the tendon, typically the supraspinatus, causing severe pain and reduced mobility.

    • Rotator cuff arthropathy:

      • Chronic tears may lead to glenohumeral joint instability, arthritis, and superior migration of the humeral head.

    • Repair and rehabilitation:

      • Tendon repair (open or arthroscopic) may be required for full-thickness tears, followed by extensive physiotherapy.

    Did you know? The tibia is the second largest bone in the body after the femur.