Arthrology and Joint Classification: Study Notes for Anatomy & Physiology

Arthrology and Kinesiology

Introduction to Arthrology

Arthrology is the scientific study of joints, their structure, function, and disorders. Joints, also known as articulations, are points where two or more bones meet, allowing for movement and providing mechanical support to the skeleton.

• Joint: A site of articulation between bones.

• Kinesiology: The study of body movement, closely related to joint function.

Classifications of Joints

Joints by Function

Joints are classified functionally based on the degree of movement they permit.

Classification	How much does it move?
Diarthrosis	Freely movable joints (e.g., shoulder, hip)
Amphiarthrosis	Slightly movable joints (e.g., intervertebral discs, pubic symphysis)
Synarthrosis	Immovable joints (e.g., sutures of the skull)

Joints by Structure

Structural classification is based on how the bones are joined together.

Classification	How does it attach?
Fibrous	Bones joined by dense connective tissue; no joint cavity
Cartilaginous	Bones joined by cartilage; no joint cavity
Synovial	Bones separated by a fluid-filled joint cavity; most movable type

Types of Joints: Examples and Classification

Specific joint types are classified by their location, structural class, and functional class.

Name	Location, Name	Structural class	Functional class
Suture	Skull	Fibrous	Synarthrosis
Syndesmosis	Distal tibiofibular joint	Fibrous	Amphiarthrosis
Gomphosis	Teeth in sockets	Fibrous	Synarthrosis
Synchondrosis	Epiphyseal plate, first sternocostal joint	Cartilaginous	Synarthrosis
Symphysis	Pubic symphysis, intervertebral discs	Cartilaginous	Amphiarthrosis
Synovial	Shoulder, hip, knee, elbow	Synovial	Diarthrosis

Synovial Joints

Unique Characteristics of Synovial Joints

Synovial joints are the most movable type of joint in the body and have several distinguishing features.

• Joint cavity: Space between articulating bones filled with synovial fluid.

• Synovial fluid and membrane: Lubricates and nourishes the joint.

• Articular cartilage and capsule: Hyaline cartilage covers bone ends; capsule encloses the joint.

• Ligaments, tendons, bursa: Provide stability and reduce friction.

Axes of Movement

Synovial joints are classified by the number of axes around which movement occurs.

• Uniaxial: Movement in one plane (e.g., hinge joint).

• Biaxial: Movement in two planes (e.g., saddle joint).

• Multiaxial: Movement in multiple planes (e.g., ball-and-socket joint).

Types of Synovial Joints

There are several types of synovial joints, each allowing specific movements.

• Gliding (Plane): Flat surfaces slide past each other (e.g., intercarpal joints).

• Hinge: Allows flexion and extension (e.g., elbow, knee).

• Pivot: Rotation around a single axis (e.g., atlantoaxial joint in the neck).

• Ellipsoidal (Condyloid): Movement in two planes (e.g., wrist joint).

• Saddle: Allows movement in two planes, with concave and convex surfaces (e.g., thumb carpometacarpal joint).

• Ball and Socket: Multiaxial movement (e.g., shoulder, hip).

Joint Movements

Types of Movements at Joints

Joints allow a variety of movements, essential for daily activities and complex motions.

Movement
Flexion / Extension
Hyperextension
Abduction / Adduction
Elevation / Depression
Protraction / Retraction
Circumduction
Lateral / Medial rotation
Opposition / Reposition
Eversion / Inversion
Pronation / Supination
Occlusion
Plantar Flexion / Dorsiflexion
Palmar Flexion / Dorsiflexion
Lateral / Medial Excursion
Intorsion / Extorsion

• Flexion: Decreasing the angle between bones.

• Extension: Increasing the angle between bones.

• Abduction: Moving away from the midline.

• Adduction: Moving toward the midline.

• Rotation: Movement around an axis.

• Circumduction: Circular movement combining flexion, extension, abduction, and adduction.

Major Synovial Joints of the Body

Shoulder Joint

The shoulder joint (glenohumeral joint) is a ball-and-socket synovial joint, allowing a wide range of motion.

• Articulating bones: Scapula and humerus.

• Features: Joint capsule, ligaments, tendons, and bursa.

Hip Joint

The hip joint is another ball-and-socket synovial joint, providing stability and mobility.

• Articulating bones: Fused hip bones and femur.

• Features: Strong ligaments and deep socket for stability.

Temporomandibular Joint (TMJ)

The TMJ connects the mandible to the temporal bone, allowing movements necessary for chewing and speaking.

• Articulating bones: Mandible and temporal bone.

• Features: Articular disc, capsule, and ligaments.

Clinical Considerations: Joint Disorders

Common Joint Disorders

Joints are susceptible to various disorders that can affect movement and cause pain.

• Gout: Inflammatory arthritis due to uric acid crystal deposition.

• Rheumatoid Arthritis: Autoimmune disorder causing joint inflammation.

• Osteoarthritis: Degenerative joint disease due to cartilage breakdown.

• Osteonecrosis: Bone tissue death due to lack of blood supply.

• Osteochondrosis: Disorders affecting bone and cartilage growth.

• Chondrocalcinosis: Calcium pyrophosphate deposition in cartilage.

• Cartilaginous Tumors: Abnormal growths in cartilage tissue.

Other Joint Injuries

• Sprain: Stretching or tearing of ligaments.

• Strain: Stretching or tearing of muscle or tendon.

• Luxation: Dislocation of a joint.

• Other Disorders: Includes various less common joint pathologies.

Summary Table: Joint Classification Overview

Structural Class	Functional Class	Example
Fibrous	Synarthrosis/Amphiarthrosis	Suture, syndesmosis, gomphosis
Cartilaginous	Synarthrosis/Amphiarthrosis	Synchondrosis, symphysis
Synovial	Diarthrosis	Shoulder, hip, knee, elbow

Additional info: Some table entries and explanations were inferred based on standard anatomical knowledge to ensure completeness and clarity.