Ch 8 Joints

Joints (Articulations) Weakest parts of the skeleton  Articulation – site where two or more bones meet Functions     Give the skeleton mobility     Hold the skeleton together

Classification of Joints: Structural Structural classification focuses on the material binding bones together and whether or not a joint cavity is present The three structural classifications are:     Fibrous     Cartilaginous     Synovial

Classification of Joints: Functional Functional classification is based on the amount of movement allowed by the joint The three functional class of joints are:     Synarthroses – immovable     Amphiarthroses – slightly movable     Diarthroses – freely movable

Fibrous Structural Joints The bones are jointed by fibrous tissues There is no joint cavity Most are immovable There are three types: Sutures Syndesmoses Gomphoses

Fibrous Structural Joints: Sutures Occur between the bones of the skull Comprised of interlocking junctions completely filled with CT fibers Bind bones tightly together, but allow for growth during youth In middle age, skull bones fuse and are called synostoses

Fibrous Structural Joints: Syndesmoses Bones are connected by a fibrous tissue ligament Movement varies from immovable to slightly variable Examples include the connection between the tibia and fibula, and the radius and ulna

Fibrous Structural Joints: Gomphoses The peg-in-socket fibrous joint between a tooth and its alveolar socket The fibrous connection is the periodontal ligament

Cartilaginous Joints Articulating bones are united by cartilage Lack a joint cavity Two types – synchondroses and symphyses

Cartilaginous Joints: Synchondroses A bar or plate of hyaline cartilage unites the bones All synchondroses are synarthrotic Examples include:     Epiphyseal plates of children     Joint between the costal cartilage of the first rib and the sternum

Cartilaginous Joints: Symphyses Hyaline cartilage covers the articulating surface of the bone and is fused to an intervening pad of fibrocartilage Amphiarthrotic joints designed for strength and flexibility Examples include intervertebral joints and the pubic symphysis of the pelvis

Synovial Joints Those joints in which the articulating bones are separated by a fluid-containing joint cavity All are freely movable diarthroses Examples – all limb joints, and most joints of the body

Synovial Joints: General Structure Synovial joints all have the following:     Articular cartilage     Joint (synovial) cavity     Articular capsule     Synovial fluid     Reinforcing ligaments

Synovial 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 Joints: Stability Stability is determined by:     Articular surfaces – shape determines what movements are possible     Ligaments – unite bones and prevent excessive or undesirable motion Muscle tone is accomplished by:     Muscle tendons across joints are the most important stabilizing factor     Tendons are kept tight at all times by muscle tone

Synovial Joints: Movement Muscle attachment across a joint Origin – attachment to the immovable bone Insertion – attachment to the movable bone Described as movement along transverse, frontal, or sagittal planes

Synovial Joints: Range of Motion Nonaxial – slipping movements only Uniaxial – movement in one plane Biaxial – movement in two planes Multiaxial – movement in or around all three planes

Gliding Movements One 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 Movement Flexion Extension Dorsiflexion and plantar flexion of the foot Abduction Adduction Circumduction

Rotation The turning of a bone around its own long axis Examples:     Between first two vertebrae     Hip and shoulder joints

Special Movements Supination and pronation Inversion and eversion Protraction and retraction Elevation and depression Opposition

Types of Synovial Joints Plane joints     Articular surfaces are essentially flat     Allow only slipping or gliding movements     Only examples of nonaxial joints Hinge joints     Cylindrical projections of one bone fits into a trough-shaped surface on another     Motion is along a single plane     Uniaxial joints permit flexion and extension only     Examples: elbow and interphalangeal joints

Pivot Joints Rounded end of one bone protrudes into a “sleeve,” or ring, composed of bone (and possibly ligaments) of another Only uniaxial movement allowed Examples: joint between the axis and the dens, and the proximal radioulnar joint

Pivot Joints

Condyloid, or Ellipsoidal, Joints Oval articular surface of one bone fits into a complementary depression in another Both articular surfaces are oval Biaxial joints permit all angular motions Examples: radiocarpal (wrist) joints, and metacarpophalangeal (knuckle) joints

Saddle Joints Similar to condyloid joints but with greater movement Each articular surface has both a concave and a convex surface Example: carpometacarpal joint of the thumb

Ball-and-Socket Joints A spherical or hemispherical head of one bone articulates with a cuplike socket of another Multiaxial joints permit the most freely moving synovial joints Examples: shoulder and hip joints

Synovial Joints: Shoulder (Glenohumeral) Ball-and-socket joint in which stability is sacrificed to obtain greater freedom of movement Head of humerus articulates with the glenoid fossa of the scapula

Synovial Joints: Shoulder Stability Weak stability is maintained by:     Thin, loose joint capsule     Four ligaments – coracohumeral, and three glenohumeral     Tendon of the long head of biceps, which travels through the intertubercular groove and secures the humerus to the glenoid cavity     Rotator cuff (four tendons) encircles the shoulder joint and blends with the articular capsule

Synovial Joints: Knee Largest and most complex joint of the body Allow flexion, extension, and some rotation Three joints in one surrounded by a single joint cavity     Femoropatellar     Lateral and medial tibiofemoral joints

Types of Joints

Synovial Joints: Major Ligaments and Tendons – Anterior View Tendon of the quadriceps femoris muscle Lateral and medial patellar retinacula Fibular collateral ligament Tibial collateral ligament Patellar ligament

Synovial Joints: Knee – Other Supporting Structures Anterior cruciate ligament Posterior cruciate ligament Medial meniscus (semilunar cartilage) Lateral meniscus

Synovial Joints: Knee – Posterior Superficial View Adductor magnus tendon Articular capsule Oblique popliteal ligament Arcuate popliteal ligament Semimembranosus tendon

Sprains The ligaments reinforcing a joint are stretched or torn Partially torn ligaments slowly repair themselves Completely torn ligaments require prompt surgical repair

Sprain

Cartilage Injuries The snap and pop of overstressed cartilage Common aerobics injury Repaired with arthroscopic surgery

Cartilage Injuries

Dislocations Occur when bones are forced out of alignment Usually accompanied by sprains, inflammation, and joint immobilization Caused by serious falls and are common sports injuries Subluxation – partial dislocation of a joint

Dislocation

Dislocation

Inflammatory and Degenerative Conditions Bursitis     An inflammation of a bursa, usually caused by a blow or friction     Symptoms are pain and swelling     Treated with anti-inflammatory drugs; excessive fluid may be aspirated       Tendonitis     Inflammation of tendon sheaths typically caused by overuse     Symptoms and treatment are similar to bursitis

Arthritis 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) 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

Osteoarthritis: Course 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

Osteoarthritis: Treatments OA is slow and irreversible Treatments include:     Mild pain relievers, along with moderate activity     Magnetic therapy     Glucosamine sulfate decreases pain and inflammation     SAM-e (s-adenosylmethionine) builds up cartilage matrix and regenerates tissue

Rheumatoid Arthritis (RA) Chronic, inflammatory, autoimmune disease of unknown cause, with an insidious onset 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 The course of RA is marked with exacerbations and remissions

Rheumatoid Arthritis: Course RA begins with synovitis of the affected joint 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

Rheumatoid Arthritis: Treatment Conservative therapy – aspirin, long-term use of antibiotics, and physical therapy Progressive treatment – anti-inflammatory drugs or immunosuppressants The drug Embrel, a biological response modifier, removes cells that promote inflammation

Gouty 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

Developmental Aspects of Joints By embryonic week 8, synovial joints resemble adult joints Few problems occur until late middle age Advancing years take their toll on joints including: Ligaments and tendons shorten and weaken Intervertebral discs become more likely to herniate OA is inevitable, and all people of 70 have some degree of OA Prudent exercise (especially swimming) that coaxes joints through their full range of motion is key to postponing joint problems