Human Anatomy & Physiology
Articulations
PowerPoint® Lectures created by Suzanne Pundt, University of Texas at Tyler
Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved
Second Edition
Module 8.1 Overview of Joints
Functions of Joints
By connecting two bones, joints perform three functions: 
•	Enable movement – link between bones allow movement when muscles and tendons exert necessary force across joint
•	Provide stability – some joints allow limited or no movement; very stable; critical for structures such as skull; protect underlying structures
•	Allow long bones to lengthen – epiphyseal plate is where long bones grow in length during skeletal development; temporary joint

Classification of Joints
Functional Classification 
Joints can be classified by how much motion they allow:
•	Synarthrosis – does not allow any movement between articulating bones
•	Amphiarthrosis – allows only a small amount of movement between articulating bones
•	Diarthrosis – freely moveable, allowing a wide variety of specific movements
Structural Classification 
Joints can be classified based on their anatomical features. 
•	Fibrous joints – fastened together by dense regular collagenous connective tissue without a joint space between articulating bones; can be synarthroses or amphiarthroses
•	Cartilaginous joints – cartilage between articulating bones without a joint space; can be synarthroses or amphiarthroses
•	Synovial joint- have a layer of hyaline cartilage on articulating surface of each bone; joint space is a fluid-filled cavity found between articulating bones, other supportive structures surround bones/enclose joint cavity, are diarthroses and provide most motion of any joint type.
Module 8.2 Structural Classification: Fibrous Joints 
Sutures
•	Suture – joint between edges of bones that make up cranium; fused sutures are very stable, well suited for protecting brain
•	-allow a small amount of movement during skeletal development, but fuse with maturity and become synarthrosis.
Gomphoses
•	Gomphosis – immoveable fibrous joint between each tooth and its bony socket in jaw; periodontal ligament is a strong fibrous membrane that links tooth firmly to jaw bone
Syndesmoses
•	Syndesmosis – joint between tibia, fibula, ulna, and radius; bones are joined by a long membrane composed of dense regular collagenous connective tissue, which allows for limited amount of movement
Fibrous Joints 
Module 8.3 Structural Classification: Cartilaginous Joints 
Synchondroses
•	Synchondrosis consists of bones united by hyaline cartilage; functionally are synarthroses:
•	Examples includes:
•	Epiphyseal plates – composed of hyaline cartilage that connects diaphyses and epiphyses of developing long bones; replaced with bone during maturation 
•	First sternocostal and costochondral joints are synchondroses that persist into adulthood
Synchondroses
Epiphyseal Plate Fractures
•	Epiphyseal plate in a child’s long bone is one of the weakest parts of a developing skeleton; even a minor injury can fracture this delicate structure, possibly with lifelong consequences [differences in limb length, limb deformities, and early-onset arthritis (joint inflammation)]
•	Most common causes include recreational activities, accidents, and competitive athletics; injuries may affect any joint but occur most often at epiphyseal plates of forearm
Epiphyseal Plate Fractures
•	Symptoms include swelling, pain, and redness over injured joint
•	Treatment depends on severity of fracture, which must be determined by careful diagnosis; minor epiphyseal plate fractures can generally be managed by immobilizing joint with a cast, but severe fractures usually require surgery
•	Many patients benefit from rehabilitation exercises to strengthen bones and muscles surrounding joint and regain full function; fortunately, most fractures do not impair bone development if managed properly
Symphyses
•	Symphysis – joint where bones are united by a tough fibrocartilage pad or plug; functionally an amphiarthrosis
•	Example of Structure-Function Core Principle; best suited for regions of skeleton that must resist compression and tension while still allowing a small amount of movement. Examples include:
•	Intervertebral joints – between adjacent vertebral bodies of spinal column 
•	Pubic symphysis – between pubic bones of pelvic girdle 
Symphyses
Module 8.4 Structural Classification: Synovial Joints 
Structural Elements 
•	Structural Elements:
•	Joint cavity (synovial cavity) – space found between articulating bones 
•	Articular capsule – double-layered structure
Structural Elements 
•	Articular capsule (continued):
o	Outer fibrous layer keeps articulating bones from being pulled apart and isolates internal environment
o	Inner layer (synovial membrane) lines entire inner surface except where hyaline cartilage is present; cells in this membrane secrete synovial fluid
o	Example of Structure-Function Core Principle: inner layer provides joint with means for obtaining life-sustaining substances and eliminating waste products
Structural Elements 
•	Synovial fluid – thick, colorless, oily liquid with the following 3 main functions: 
•	Provides lubrication – reduces friction between articulating surfaces of a joint
•	Serves metabolic functions; supplies nutrients and removes metabolic waste 
•	Provides shock absorption; helps to evenly distribute stress and force placed on articular surfaces during movement
Structural Elements 
•	Articular cartilage – composed of hyaline cartilage; covers all exposed articulating bones within a joint
•	Provides a smooth surface for articulating bones to interact; reduces friction and absorbs shock, illustration of Structure-Function Core Principle 
•	Articular cartilage is avascular; cells rely on synovial fluid for oxygen, nutrients, and waste removal
•	Other components of a synovial joint include adipose tissue, nerves, and blood vessels
Structural Elements 
Stabilizing and Supporting Factors
•	Synovial joints allow more mobility but are less stable than other joint types; the following structures provide additional stabilization:
-Articular capsule provides some structural support
-Ligament– strand of dense regular collagenous connective tissue; links one bone to another; provides additional strength and reinforcement to a joint
Stabilizing and Supporting Factors
•	Tendon – structural component of skeletal muscle; composed of dense regular collagenous connective tissue and connects muscle to bone
o	Tendons typically cross over or around a joint so that when a muscle contracts the force generated is transmitted across the joint. 
o	Muscles to which the tendons attach also help stabilize joints. Muscles constantly generate small contractions known as muscle tone.
Stabilizing and Supporting Factors
•	Bursae and tendon sheaths also provide joint stabilization and support
o	Bursa – synovial fluid-filled fibrous structure helps to minimize friction between all moving parts associated with joints
o	Tendon sheath – long bursa that surrounds some tendons; in high-stress regions, protects tendons as they slide over/around joint
Stabilizing and Supporting Factors
Bursitis
•	Bursitis refers to inflammation of a bursa; can result from a single traumatic event such as a fall, repetitive movements like pitching a baseball, or an inflammatory disease such as rheumatoid arthritis
•	Most common sites of bursitis are shoulder, elbow, hip, and knee
•	Clinical features of bursitis include pain both at rest and with motion of affected joint; joint may feel tender, swollen, and warm
Bursitis
•	Treatment – aimed primarily at reducing pain and swelling; rest, ice, compression of injured area, and medications are beneficial in early stages of injury
•	Anti-inflammatory steroid medications may be injected directly into bursa itself; fluid can also be removed from bursa to relieve swelling
•	Left untreated, bursitis can become chronically painful and increasingly difficult to cure
Arthritis 
•	Arthritis – defined as inflammation of one or more joints which results in pain and limitations of joint movement; three common types of arthritis include:
•	Osteoarthritis – most common form; generally associated with wear and tear; common features include pain, joint stiffness, and decreased mobility
•	Rheumatoid arthritis – associated with joint destruction mediated by individual’s own immune system
•	Gouty arthritis – causes joint damage by generating an inflammatory reaction to uric acid crystal deposits
Module 8.5 Function of Synovial Joints
Functional Classes of Synovial Joints
•	Bones in a synovial joint move in different planes around an axis or axes; different possible joint configurations include:
•	Nonaxial joints – allow motion to occur in one or more planes without moving around an axis
•	Uniaxial joints – allow motion around only one axis
•	Biaxial joints – allow motion around two axes
•	Multiaxial (triaxial) joints – allow motion around three axes
Concept Boost: Understanding Axes of Motion 
•	Elbow joint has only one axis (axis 1 in figure) and acts like a hinge; allows motion in one plane perpendicular to axis
•	Allows forearm and hand to move 
upward toward shoulder or to 
make opposite movement away 
from shoulder
Concept Boost: Understanding Axes of Motion 
•	Metacarpophalangeal joints – biaxial, between proximal phalanges and metacarpals
•	Can move around axis 1, allowing proximal phalanges to move toward and away from palm of hand (same as elbow joint)
•	Can also move around axis 2, allowing fingers to be squeezed together or fanned out
Concept Boost: Understanding Axes of Motion 
•	Third axis allows an additional motion that uniaxial and biaxial joints are not able to perform; shoulder is an example of a multiaxial joint
•	Humerus can move forward and backward around axis 1 (as when you swing arms back and forth while walking)
•	Humerus can also move away from and toward your body around axis 2 (as when you do jumping jacks)
•	Humerus can rotate (move in a circular fashion) around axis 3 (as when you throw a Frisbee)
Concept Boost: Understanding Axes of Motion 
Movements at Synovial Joints
•	Four general types of movement can take place at a synovial joint:
•	Gliding movements – gliding is a sliding motion between articulating surfaces that is nonaxial 
•	Angular movements – increase or decrease angle between articulating bones
Movements at Synovial Joints
Movements at Synovial Joints
•	Specific types of angular motion:
•	Flexion – decreases angle between articulating bones by bringing bones closer to one another
•	Extension – increases angle between articulating bones, is opposite of flexion; articulating bones move away from one another
•	Hyperextension – extension beyond anatomical position of joint
Movements at Synovial Joints
Movements at Synovial Joints
•	Specific types of angular motion (continued):
•	Abduction – motion of a body part away from midline of body or another reference point 
•	Adduction – motion of a body part towards midline of body or another reference point; opposite of abduction
Movements at Synovial Joints
•	Specific types of angular motion (continued):
•	Circumduction– only unpaired angular movement where a freely moveable distal bone moves around a fixed proximal bone in a cone-shaped motion; combination of flexion-extension and abduction-adduction
Movements at Synovial Joints
Movements at Synovial Joints
•	Rotation – nonangular motion in which one bone rotates on an imaginary line running down its middle longitudinal axis
Movements at Synovial Joints
•	Special Movements include those types not otherwise defined by previous categories:
•	Opposition and reposition: opposition of thumb at first carpometacarpal joint allows thumb to move across palmar surface of hand; reposition is opposite movement that returns thumb to its anatomical position
•	Depression and elevation: depression is movement of a body part in an inferior direction while elevation moves a body part in a superior direction
Movements at Synovial Joints
Movements at Synovial Joints
•	Special Movements (continued):
•	Protraction and retraction: protraction moves a body part in an anterior direction; retraction moves a body part in a posterior direction 
•	Inversion and eversion: inversion is a rotational motion in which plantar surface of foot rotates medially toward midline of body; eversion rotates foot laterally away from midline
Movements at Synovial Joints
Movements at Synovial Joints
•	Special Movements (continued):
•	Dorsiflexion and plantarflexion: dorsiflexion is a movement where angle between foot and leg decreases; angle between foot and leg increases during plantarflexion
Movements at Synovial Joints
•	Special Movements (continued):
•	Supination and pronation: rotational movements of wrist and ankle regions
Study Boost: Keeping Supination and Pronation Straight 
•	Supination vs. pronation: you hold a cup of soup when your hand is supinated, and you pour it out when your hand pronates
•	Abduction vs. adduction: with abduction, you abduct (take away) part from body; with adduction, you add part back to body
Range of Motion
•	Range of Motion: amount of movement joint is capable of under normal circumstances 
•	When you move your knee joint from a relaxed state to full flexion, and then return joint to its fully extended state, that is range of motion of knee
•	Uniaxial joints (such as knee) tend to have smallest range of motion; multiaxial joints (such as shoulder) tend to have greatest
Module 8.6 Types of Synovial Joints
Types of Synovial Joints
•	Plane joint (gliding joint) – most simple and least mobile, features 2 bones whose flat surfaces sit next to each other.
Types of Synovial Joints
•	Hinge joint – convex articular surface of one bone fits into concave depression of a second bone; allows for uniaxial movement
Types of Synovial Joints
•	Pivot joint – rounded surface of one bone fits into a groove on surface of a second bone, allowing for uniaxial movement, pivots or rotates on longitudinal axis
Types of Synovial Joints
•	Condylar or ellipsoid joint – biaxial joint where oval, convex surface of one bone fits into a shallow, concave articular surface of a second bone
Types of Synovial Joints
•	Saddle joint – each articulating bone surface has both a concave and convex region that complement one another; allows a great deal of motion for a biaxial joint 
Types of Synovial Joints
•	Ball-and-socket joint – multiaxial joint in which articulating surface of one bone is spherical and fits into a cup-shaped depression in second bone; allows motion in all three axes

Specific Hinge Joints 
Elbow –composed of two articulations and three strong ligaments that support articular capsule, more stable than knee:
•	Humeroulnar joint – larger articulation; between trochlea of humerus and trochlear notch of ulna
•	Humeroradial joint – smaller articulation between capitulum of humerus and head of radius
Specific Hinge Joints 
Elbow (continued):
•	Radial collateral ligament (lateral collateral ligament) supports lateral side of joint
•	Ulnar collateral ligament (medial collateral ligament) supports medial side of joint
•	Anular ligament binds head of radius to neck of ulna; stabilizes radial head
Specific Hinge Joints 
A&P Flix: Movement at the Elbow Joint
Specific Hinge Joints 
•	Knee:
•	Patellar ligament – distal continuation of quadriceps tendon 
•	Tibiofemoral joint – articulation between femoral and tibial condyles
•	Patellofemoral joint – articulation between patella and anterior patellar surface of femur
Specific Hinge Joints 
•	Knee (continued):
•	Medial and lateral meniscus – C-shaped fibrocartilage pads sit on tibial condyles; provide shock absorption and cushioning between articular cartilages of femoral and tibial condyles, also further stabilize the joint
•	Two collateral ligaments (medial and lateral)- located on either side of the knee joint, tighten when knee is extended to provide additional stability during weight bearing and walking.
Specific Hinge Joints 
Specific Hinge Joints 
A&P Flix: Movement at the Knee Joint
Knee Injuries and the 
Unhappy Triad
•	Despite supportive structures, knee joint is still susceptible to injury; any activity that involves quick changes in direction can injure knee
•	Athletes who participate in contact sports (football or soccer) are also at risk, especially if knee is struck from side or from behind
•	A lateral blow (like an illegal block below knees) often ruptures tibial collateral ligament; medial meniscus and anterior cruciate ligament may tear as well, creating the “unhappy triad”
•	Fibular collateral and posterior collateral ligaments can also be damaged, but this is less common
Knee Injuries and the 
Unhappy Triad
Knee Injuries and the 
Unhappy Triad
•	Treatment depends on their severity:
•	Initial interventions include rest, ice, compression, and anti-inflammatory medications to reduce swelling and minimize pain
•	More severe injuries may require surgical repair of damaged ligaments
•	Physical therapy and rehabilitation to strengthen surrounding muscles are also helpful
Specific Ball-and-Socket 
Joints
•	Shoulder (glenohumeral joint) – one of the articulations of pectoral girdle, connects upper extremity with axial skeleton; composed of ball-shaped head of humerus and glenoid cavity on lateral scapula:
•	Most freely moving joint in body, however, greater mobility comes at the price of less stability/increased risk of injury.
•	Glenoid labrum – fibrocartilaginous ring; sits on the rim of the glenoid cavity, helps support joint

•	Shoulder (continued):
•	Biceps brachii tendon – this tendon and muscle tone of the upper arm provide a stabilizing force that keeps the humeral head firmly in glenoid cavity. 
•	Supraspinatus, infraspinatus, subscapularis, and teres minor, these muscles and corresponding tendons are collectively called the rotator cuff. The rotator cuff surrounds the shoulder joint and provides most of its strength and stability.
Specific Hinge Joints 
Specific Hinge Joints 
Specific Hinge Joints 
A&P Flix: Movement at the Glenohumeral Joint: An Overview 
A&P Flix: Movement at the Glenohumeral Joint: An Overview 
Shoulder Dislocations
•	Mobility of shoulder joint comes at expense of stability; shoulder injuries are very common, accounting for more than half of all joint dislocations 
•	Dislocated shoulder – specific to glenohumeral joint; head of humerus is traumatically displaced from glenoid cavity
•	Separated shoulder – another common injury, specific to acromioclavicular joint; not actually a component of shoulder
Shoulder Dislocations
•	Contact sport athletes are especially susceptible to shoulder injuries, but anyone can suffer them under the right circumstances
•	Any fall in which hand and forearm are outstretched can result in a dislocation injury; impact may force head of humerus through inferior wall of articular capsule (weakest relative to rest of capsule)
Shoulder Dislocations
•	Chest wall muscles pull dislocated humeral head superiorly and medially; head comes to rest inferior to coracoid process of scapula
•	Makes shoulder look flattened or “squared off”; injured person often holds wrist of affected shoulder against abdomen, the least painful position
•	Some minor shoulder dislocations can “pop” back into place with limited effort; more severe injuries may need to be surgically repaired
Specific Ball-and-Socket 
Joints
•	Hip (coxal joint) –articulation between acetabulum and ball-shaped head of femur; much more stable than shoulder because of its role in weight bearing and locomotion. 
•	This increased stability comes with some reduction in mobility (especially compared to shoulder)
•	This joint derives its support from a strong articular capsule, the many large and powerful muscle groups that surround it, and a number of reinforcing ligaments.

Hip Joint Replacement Surgery
•	Hip replacement – surgical procedure that replaces a painful damaged joint with an artificial prosthetic device; individual may elect to have a hip replaced due to debilitating pain and subsequent loss of joint function
•	Severe arthritis, trauma, fractures, and bone tumors can all progress to point where hip joint replacement is an option
A&P Flix: Movement at the Hip Joint: An Overview
A&P Flix: Movement at the Hip Joint
Hip Joint Replacement Surgery
•	Total replacement removes and replaces head of femur and reconstructs acetabulum 
•	Partial replacement removes only head of femur; replaces it with a prosthetic device, leaving acetabulum intact
•	Choice of replacement depends 
on many factors, including type 
of injury, patient’s age, and general health
Hip Joint Replacement Surgery
•	Surgical complications are rare, further minimized with good postprocedure follow-up care
•	Rigorous rehabilitation program usually follows surgery to restore normal function as soon as possible; may take 3–6 weeks for patient to completely return to normal daily activities