Articulations (Joints)Articulations (Joints)Chapter 8Chapter 8

Articulations (Joints)Articulations (Joints)Chapter 8Chapter 8

Weakest parts of the skeletonWeakest parts of the skeleton

Introduction to JointsIntroduction to Joints Articulation – site where two or more bones meet

Functions of joints

o Give the skeleton mobility

o Hold the skeleton together

Structural classification focuses on the material binding bones together and whether or not a joint cavity is present

The three structural classifications are:

Functional classification is based on the amount of movement allowed by the joint

The three functional classes of joints are:

o Fibrous

o Synarthroses – immovable

o Cartilaginous

o Synovial

o Amphiarthroses – slightly movable

o Diarthroses – freely movable

Fibrous JointsFibrous Joints

Sutures occur between bones of skull and use very short connective tissue fibers to hold the bones together.

o Synostoses – fused in adult

In syndesmoses, the bones are connected by a ligament, which is a cord or band of fibrous tissue.

A gomphosis is a peg-in-socket fibrous joint.

Cartilaginous JointsCartilaginous Joints

Synchondroses involve a bar or plate of hyaline cartilage uniting the bones, such as the epiphyseal plate.

In symphyses, such as the pubic symphysis, the articular surfaces are covered with articular cartilage that is then fused to an intervening pad or plate of fibrocartilage.

Hyaline Cartilage

Synovial Joints

Those joints in which the articulating bones are separated by a fluid-containing joint cavityAll are freely movable diarthrosesExamples – all limb joints, and most joints of the body

General Structure

Synovial Joints: Friction-Reducing StructuresSynovial Joints: Friction-Reducing Structures

Bursae – flattened, fibrous sacs lined with synovial membranes and containing synovial fluid

Common where ligaments, muscles, skin, tendons, or bones rub together

Tendon sheath – elongated bursa that wraps completely around a tendon

Synovial Joint StabilitySynovial Joint StabilityStability is determined by:

o Articular surfaces – shape determines what movements are possibleo Ligaments – unite bones and prevent excessive or undesirable motiono Labrums and menisci that deepen the articular surface

o Muscle tone is accomplished by: Muscle tendons across joints acting as stabilizing factors Tendons that are kept tight at all times by muscle tone

o Fat pads – protect nerves and blood vessels

Synovial Joints: Range of MotionSynovial Joints: Range of MotionNonaxial (translational) – slipping movements only

Uniaxial – movement in one plane

Biaxial – movement in two planes

Multiaxial – movement around all three planes

Gliding MovementsGliding MovementsOne flat bone surface glides or slips over another similar surface

Examples – intercarpal and intertarsal joints, and between the flat articular processes of the vertebrae

Angular MovementAngular Movement

Angular MovementAngular Movement

Angular MovementAngular Movement

RotationRotationThe turning of a bone around its own long axis

Examples

o Between first two vertebrae

o Hip and shoulder joints

Special MovementsSpecial Movements

Special MovementsSpecial Movements

Special MovementsSpecial Movements

Special MovementsSpecial Movements

Synovial Joint: Synovial Joint: Knee

Largest and most complex joint of the bodyAllows flexion, extension, and some rotationThree joints in one surrounded by a single joint cavity

o Femoropatellar

o Lateral and medial tibiofemoral joints

Ligaments and tendons

o Quadriceps tendon

o Lateral and medial patellar retinacula

o Fibular and tibial collateral ligaments

o Patellar ligament

Synovial Joints: Knee – Other Supporting Structures

Anterior cruciate ligament

Posterior cruciate ligament

Medial meniscus

Lateral meniscus

Shoulder (Glenohumeral)Ball-and-socket joint - stability is sacrificed for greater freedom of movement

Head of humerus articulates with the glenoid fossa of the scapula

Weak stability is maintained by:

o Thin, loose joint capsule

o Four ligaments – coracohumeral, and three glenohumeral

o Tendon of the long head of biceps, which travels through the intertubercular groove and secures the humerus to the glenoid cavity

o Rotator cuff that encircles shoulder joint and blends with articular capsule

Hip (Coxal) Joint

Ball-and-socket joint

Head of the femur articulates with the acetabulum

Good range of motion, but limited by the deep socket and strong ligamentso Acetabular labrum

o Iliofemoral ligament

o Pubofemoral ligament

o Ischiofemoral ligament

o Ligamentum teres

InjuriesInjuries

Sprains

o The ligaments reinforcing a joint are stretched or torn

o Partially torn ligaments slowly repair themselves

o Completely torn ligaments require prompt surgical repair

Cartilage Injuries

o The snap and pop of overstressed cartilage

o Common aerobics injury

o Repaired with arthroscopic surgery

Dislocations

o Occur when bones are forced out of alignment

o Usually accompanied by sprains, inflammation, and joint immobilization

o Caused by serious falls and are common sports injuries

o Subluxation – partial dislocation of a joint

Inflammatory and Degenerative ConditionsInflammatory and Degenerative Conditions

Bursitis

o An inflammation of a bursa, usually caused by a blow or friction

o Symptoms are pain and swelling

o Treated with anti-inflammatory drugs; excessive fluid may be aspirated

Tendonitis

o Inflammation of tendon sheaths typically caused by overuse

o Symptoms and treatment are similar to bursitis

ArthritisArthritis

Osteoarthritis (OA)Osteoarthritis (OA)Most common chronic arthritis; often called “wear-and-tear” arthritis

Affects women more than men

85% of all Americans develop OA

More prevalent in the aged, and is probably related to the normal aging process

More than 100 different types of inflammatory or degenerative diseases that damage the joints

Most widespread crippling disease in the U.S.

Symptoms – pain, stiffness, and swelling of a joint

Acute forms are caused by bacteria and are treated with antibiotics

Chronic forms include osteoarthritis, rheumatoid arthritis, and gouty arthritis

Osteoarthritis (OA)Osteoarthritis (OA)

Course of the DiseaseCourse of the Disease

o OA reflects the years of abrasion and compression causing increased production of metalloproteinase enzymes that break down cartilage

As one ages, cartilage is destroyed more quickly than it is replaced

The exposed bone ends thicken, enlarge, form bone spurs, and restrict movement

Joints most affected are the cervical and lumbar spine, fingers, knuckles, knees, and hips

Treatmentso OA is slow and irreversible

Treatments include:

o Mild pain relievers, along with moderate activity

o Magnetic therapy

o Glucosamine sulfate decreases pain and inflammation

Rheumatoid Arthritis (RA)

Chronic, inflammatory, autoimmune disease of unknown cause

Usually arises between the ages of 40 to 50, but may occur at any age

Signs and symptoms include joint tenderness, anemia, osteoporosis, muscle atrophy, and cardiovascular problems

Course

RA begins with synovitis of the affected joint

Inflammatory chemicals are inappropriately released

Inflammatory blood cells migrate to the joint, causing swelling

Inflamed synovial membrane thickens into a pannus

Pannus erodes cartilage, scar tissue forms, articulating bone ends connect

The end result, ankylosis, produces bent, deformed fingers

TreatmentConservative therapy – aspirin, long-term use of antibiotics, and physical therapy

Progressive treatment – anti-inflammatory drugs or immunosuppressants

The drug Enbrel, a biological response modifier, neutralizes the harmful properties of inflammatory chemicals

Gouty ArthritisGouty Arthritis

Deposition of uric acid crystals in joints and soft tissues, followed by an inflammation response

Typically, gouty arthritis affects the joint at the base of the great toe

In untreated gouty arthritis, the bone ends fuse and immobilize the joint

Treatment – colchicine, nonsteroidal anti-inflammatory drugs, and glucocorticoids