Joint Structure and Function

A comprehensive set of practice flashcards covering the major concepts from the lecture notes on joints, including classifications, structures, synovial joint components, development, and synovial fluid analysis.

What is Arthrology?

The study of joints, their diseases, and treatments.

What are the four functional roles of joints?

Transmission of forces (tension, compression, shear, and torsion); differential growth; movement and locomotion.

What is the functional classification of joints?

Synarthrosis (very limited/no movement), Amphiarthrosis (limited movement), Diarthrosis (freely movable).

What is the anatomical classification of joints?

Fibrous, Cartilaginous, Bony, Synovial.

What is the combined classification of joints?

Fibrous synarthrodial (very limited movement), Cartilaginous amphiarthrodial (limited movement), Synovial diarthrodial (freely movable).

What are synarthrosis joints?

Fibrous joints with dense irregular connective tissue and little to no movement.

Name the fibrous synarthrosis types.

Sutures, Gomphosis, Syndesmosis.

Describe sutures.

Two bones initially separated fuse together via dense, fibrous connective tissue.

Describe gomphosis.

Conical peg fits into a socket.

Describe syndesmosis.

Fibrous articulations bound by interosseous ligaments or fibrous membranes.

What is a synarthrosis with a bony union?

Synostosis—two or more bones connected by a bony union.

What is a cartilaginous synarthrosis?

Synchondrosis—bones joined by hyaline cartilage.

What is primary synchondrosis?

A hyaline cartilage growth plate (epiphyseal plate) between metaphysis ends of a long bone that allows growth.

What is an amphiarthrosis of cartilaginous type?

Symphysis—fibrocartilage between bones allowing limited motion.

What are synovial joints?

Joints that are freely movable (diarthrodial).

What are the key structural features of synovial joints?

A fibrous capsule, articular cartilage on bone ends, a synovial membrane lining the joint, and a synovial fluid-filled cavity; bones do not contact each other directly.

What are the categories of accessory ligaments?

Capsular (thickening of the capsule), Extracapsular (outside the capsule), Intracapsular (inside the capsule).

What are articular discs or menisci?

Fibrocartilaginous structures between bones to improve fit and distribute load.

What is the role of muscles and tendons in synovial joints?

Important for the integrity and stability of joints.

What are the properties of articular cartilage?

Covers bone ends; wear resistant; low friction; lubricated by synovial fluid; elastic; compressible; absorbs compression and shear.

What is the synovial membrane?

A specialized membrane lining the inner surface of joint capsules, tendon sheaths, and bursae; not lining articular cartilage.

What is unique about the synovial membrane’s vascularization?

Dense network of vessels; highly vascular; pathogens can spread from blood to joint.

What are the two layers of the synovium?

Intima (produces/cleans synovial fluid) and Sub-intima (nerves, blood vessels, lymphatics).

What is the function of synovial fluid?

Lubricates joints; boundary lubrication with lubricin; viscosity increased by hyaluronan to aid lubrication.

How is cartilage nourished given its avascularity?

Nutrients are delivered via synovial fluid.

What is the typical composition of synovial fluid?

Filtrate of plasma containing hyaluronic acid, lubricin, proteases, collagenases; few leukocytes (<200/mL); mostly mononuclear; clear to slightly yellow; highly viscous; no microorganisms or crystals.

What is a normal synovial fluid WBC count?

Less than 200 cells per microliter (mL).

What WBC range characterizes noninflammatory synovial fluid?

Less than 2000 cells/mL (typically <200-2000).

What WBC range characterizes inflammatory synovial fluid?

Approximately 2,000 to 50,000 cells/mL.

What WBC range characterizes septic synovial fluid?

Greater than 50,000 cells/mL.

Which joints are examples of pivot joints?

Atlantoaxial joint and radioulnar joints.

Which joints are examples of plane joints?

Carpometacarpal joints (facilitating gliding movements).

Which joints are examples of hinge joints?

Elbow joint (flexion and extension).

Which joints are examples of saddle joints?

Metacarpophalangeal joint of the thumb (first MCP).

Which joints are examples of condyloid joints?

Wrist (radiocarpal) joints; biaxial with flexion/extension, abduction/adduction, and circumduction.

Which joints are examples of ball-and-socket joints?

Hip and shoulder joints; multiaxial with movement in several axes.

Why is the study of synovial joints important in medicine?

Understanding etiology, diagnosis, and management of joint diseases; synovial fluid analysis and imaging are key tools.

What is the difference between synovial and non-synovial joints?

Synovial joints have a joint cavity with synovial fluid and a synovial membrane; non-synovial joints lack a true joint cavity and synovial fluid.