Anatomy of the Human Joints and Ligaments
Joints and Ligaments of the Human Body
Spine and Head
Joints of the Spine with the Head
Occipital Joint
Connects the occipital bone’s condyles with the atlas’s articular processes. Reinforced by the capsule and ligaments.
Atlantoaxial Joint
Comprises two joints:
- Atlantoaxial (connects the articular processes of the atlas and axis)
- Atlanto-odontoid (connects the atlas’s outer arch to the axis’s dens)
These joints are reinforced by ligaments.
Spinal Joints
Joints of the Vertebral Bodies
Cartilaginous joints formed by the vertebral bodies’ upper and lower faces. Joined by intervertebral discs (nucleus pulposus and annulus fibrosis) acting as ligaments. The nucleus pulposus facilitates flexion, extension, tilting, and rotation.
Ligaments of the Spine
Ligaments of Vertebral Bodies
- Anterior Longitudinal Ligament: Located in front of the vertebral body.
- Posterior Longitudinal Ligament: Located within the vertebral foramen, coating the bodies.
Ligaments of Vertebral Arches
- Ligamentum Flavum: Lines the back of the vertebral foramen.
Interapophyseal Ligaments
- Intertransverse Ligament: Connects transverse processes.
- Interspinous Ligament: Connects spinous processes.
- Supraspinous Ligament: Located above the spinous processes.
Other Spinal Structures and Joints
Joints of the Articular Processes
Shaped by movement direction. United by a capsule reinforced by ligaments. Crucial for bending.
Union of Spinous Processes
Connected via interspinous and supraspinous ligaments. The interspinous ligament fills the space between spinous processes, while the supraspinous ligament extends along the spine, connecting them.
Union of Transverse Processes
Connected by intertransverse ligaments. In the cervical region, these are replaced by intertransverse muscles.
Lumbosacral Joint
Connects L5 and S1, governing spinal movement relative to the pelvis.
Sacrococcygeal Joint
Cartilaginous joint with a ligament, enabling dorsal flexion and extension.
Spinal Movements
- Flexion-Extension: Occurs on the horizontal axis and sagittal plane (250° range).
- Lateral Bending: Occurs on the anteroposterior axis and frontal plane.
- Rotation: Primarily occurs in the back and atlantoaxial joint.
Upper Limb Joints
Sternoclavicular Joint
Connects the manubrium and first costal cartilage to the clavicle. Contains an articular disc. Includes the joint capsule and anterior, posterior, superior, and inferior ligaments. A saddle joint with limited mobility, enabling elevation, protraction, retraction, and circumduction.
Acromioclavicular Joint
Connects the clavicle’s extremity to the acromion. An artrodial joint with limited movement. Includes the acromioclavicular joint capsule, ligaments, coracoclavicular and coracoacromial ligaments.
Shoulder Joint (Glenohumeral Joint)
Connects the scapula to the humerus. Articular surfaces are the glenoid fossa and humeral head. Contains three bursae. Includes the joint capsule, glenohumeral ligaments, and periarticular muscles. A ball-and-socket joint enabling flexion, extension, adduction, abduction, rotation, and circumduction.
Elbow Joint
- Humeroantebrachial Joint: Connects the humerus with the ulna and radius. A trochlear joint allowing flexion and extension.
- Superior Radioulnar Joint: Connects the radius and ulna, involved in pronosupination. A trochoid joint.
The joint surfaces include the humeral trochlea, capitellum, radial fovea and circumference, ulnar trochlear notch. Includes the joint capsule, anterior, posterior, lateral, internal, and external ligaments. Enables flexion, extension, pronation, and supination.
Inferior Radioulnar Joint
A trochoid joint enabling supination and pronation. Contains an articular disc. Articular surfaces are the ulnar notch of the radius and ulnar head. Includes the joint capsule, anterior and posterior radioulnar ligaments, and the triangular ligament.
Radiocarpal Joint
Connects the glenoid fossa and condyle. Includes the capsule, anterior, posterior, lateral, ulnar, and radial ligaments. A condyloid joint enabling flexion, extension, abduction, adduction, and circumduction.
Carpal Joints
- Within Rows: First row (diarthrodial), second row (condylar).
- Between Rows: Condylar joint connecting the two rows.
Hand Joints
- Carpometacarpal: First finger (saddle), others (arthrodial).
- Intermetacarpal: Arthrodial.
- Metacarpophalangeal (MCP): Condylar.
- Interphalangeal (IP): Hinge (thumb has only one).
Forearm Muscles: Posterior Compartment
Superficial Layer
- Extensor Carpi Radialis Longus: Originates from the lateral epicondyle of the humerus and inserts at the base of the 2nd metacarpal. Performs wrist extension and radial inclination.
- Extensor Carpi Radialis Brevis: Originates from the lateral epicondyle of the humerus and inserts into the base of the 3rd metacarpal. Performs wrist extension and radial inclination.
- Extensor Carpi Ulnaris: Originates from the medial epicondyle and posterior border of the ulna, inserting at the base of the 5th metacarpal. Performs wrist extension and adduction.
- Extensor Digitorum: Originates from the lateral epicondyle of the humerus and inserts into the phalanges. Performs finger and wrist extension.
- Extensor Digiti Minimi: Originates from the epicondyle of the humerus and olecranon of the ulna, inserting into the back of the little finger. Performs little finger and wrist extension and ulnar deviation.
Deep Layer
- Abductor Pollicis Longus: Originates from the back of the ulna and radius, inserting into the outer face of the 1st metacarpal. Performs radial abduction, thumb abduction, and wrist extension.
- Extensor Pollicis Brevis: Originates from the posterior aspect of the radius and ulna, inserting on the base of the thumb. Performs wrist and thumb extension and radial abduction.
- Extensor Pollicis Longus: Originates from the back of the ulna and interosseous membrane, inserting into the base of the 2nd phalanx of the thumb. Performs extension of the 1st phalanx on the 2nd, wrist extension, and radial abduction.
- Extensor Indicis Proprius: Originates from the posterior ulna and interosseous membrane, inserting into the distal phalanx of the index finger. Performs index finger and wrist extension and radial abduction.