Chapter 8... Joints

Sutures

Occur between bones of the skull and use very short connective tissue fibers to hold the bones together. ONLY in the skull. Synarthrosis.

Dislocations

Occur when the bones are forced out of alignment.

Sprains

Occur when the ligaments reinforcing a joint are stretched or torn.

Cartilage Tears

Often occur at the knee, when a meniscus is subjected to compression and shear stress at the same time

Gliding Movement

One flat, or nearly flat, bone surface glides or slips over another. (moving the wrist when you wave)

Gomphosis

Peg-in-socket fibrous joint. Only example is teeth in its alveolar socket by the fibrous, periodontal ligament. Synarthrosis.

Saddle Joints

Consist of each articular surface bearing complementary concave and convex areas, and allow more freedom of movement than condyloid joints

Functional Classification

Movement allowed at the joint Synarthroses: Immovable joints Amphiarthroses: Slightly movable joints Diarthroses: Freely movable joints, mostly in limbs

Structure of Synovial Joints

All synovial joints have a joint cavity enclosed by a fibrous layer lined with synovial membrane and reinforced by ligaments. Connecting bone ends covered with articular cartilage and synovial fluid in the joint cavity. Some (knee) contain fibrocartilage discs that absorb shock.

Symphyses (sim fih sis)

Articular surfaces are covered with articular cartilage that is then fused to an intervening pad or plate of fibrocartilage. Amphiarthroses. Intrevertebral joints and the pubic symphysis of the pelvis.

Orgin

Attached to the immovable (less movable) bone.

Insertion

Attached to the movable bone.

Bursae and Tendon Sheaths

Bags of lubricant that reduce friction at synovial joints

Synchondroses (sin kon dro sis)

Bar or plate of hyaline cartilage uniting the bones. Almost all are synchondroses. Epiphyseal plate in long bones of children and the joint between the costal cartilage of the first rib and the manubrium of the sternum.

Syndesmosis

Bones are connected by a ligament, which is a cord or band of fibrous tissue. If fibers are short, little or no movement. If fibers are long, a large amount of movement is possible. Amphiarthrosis.

Fibrous Joints

Bones are connected by fibrous tissue, no joint cavity. Nearly all fibrous joints are synarthrotic. Three types are sutures, syndesmosis, and gomphosis.

Cartilaginous Joints

Bones are joined together by cartilage and they lack a joint cavity. Not highly moveable. Two types: Synchondroses and symphyses

Rheumatoid Arthritis

Chronic inflammatory disorder that is an autoimmune disease.

Synovial Joints

Connecting bones are separated by a fluid-containing joint cavity. Diarthroses.

Hinge Joints

Consist of a cylindrical projection that nests in a trough-shaped structure, and allow movement along a single plane.

Pivot Joints

Consist of a rounded structure that protrudes into a sleeve or ring, and allow uniaxial rotation of a bone around the long axis.

Ball-and-Socket Joints

Consist of a spherical or hemispherical structure that articulates with a cuplike structure. They are the most freely moving joints and allow multiaxial movements.

Condyloid or Ellipsoid Joints

Consist of an oval articular surface that nests in a complementary depression, and permit all angular movements.

Arthritis

Describes many inflammatory or degenerative diseases that damage the joints, resulting in pain, stiffness, and swelling of the joint.

Knee Joint

Enclosed in one joint cavity, the knee joint is actually three joints in one: the femoropatellar joint, the lateral and medial joints between the femoral condyles, and the menisci of the tibia, known collectively as the tibiofemoral joint. Many different types of ligaments stabilize and strengthen the capsule of the knee joint. The knee capsule is reinforced by muscle tendons such as the strong tendons of the quadriceps muscles and the tendon of the semimembranosus.

Plane Joints

Flat articular surfaces and allow gliding and transitional movements.

Angular Movements

Increase or decrease the angle between two bones. Flexion decreases the angle of the joint and brings the articulating bones closer together. Extension increases the angle between the articulating bones. Dorsiflexion decreases the angle between the top of the foot (dorsal surface) and the anterior surface of the tibia. Plantar flexion decreases the angle between the sole of the foot (plantar surface) and the posterior side of the tibia. Abduction is the movement of a limb (or fingers) away from the midline body (or of the hand). Adduction is the movement of a limb (or fingers) toward the midline of the body (or the hand). Circumduction is moving a limb so that it describes a cone in the air.

Bursitis

Inflammation of the bursa, is usually caused by a blow or friction.

Tendonitis

Inflammation of the tendons, and is usually caused by overuse.

Lyme Disease

Inflammatory condition caused by a type of spirochete bacteria transmitted by the bites of ticks living on deer and mice.

Developmental Aspects of Joints

Joints develop at the same time as bones, resembling adult form by eight weeks gestation. At late middle age and beyond, ligaments and tendons shorten and weaken, intervertebral discs become more likely to herniate, and there is onset of osteoarthritis

Structrual Classification

Material binding the bones together and whether or not a joint cavity is present Fibrous joints Cartilaginous joints Synovial joints

Osteoarthritis

Most common chronic arthritis. It is the result of breakdown of articular cartilage and thickening of bone tissue, which may restrict joint movement.

Gouty Arthritis

Results when uric acid is deposited in the soft tissues of the joints.

Joints or Articulations

Site where two or more bones meet.

Shoulder (Glenohumeral) Joint

Stability has been sacrificed to provide the most freely moving joint in the body. The ligaments that help to reinforce the shoulder joint are the coracohumeral ligament and the three glenohumeral ligaments. The tendons that cross the shoulder joint and provide the most stabilizing effect on the joint are the tendon of the long head of the biceps brachii and the four tendons that make up the rotator cuff.

Classification of Joints

Structural classification: material binding the bones together and if a joint cavity is present Functional classification: movement allowed at the joint

Other Special Movements

Supination is rotating the forearm laterally so that the palm faces anteriorly or superiorly. Pronation is rotating the arm medially so that the palm faces posteriorly or inferiorly. Inversion turns the sole of the foot so that it faces medially. Eversion turns the sole of the foot so that it faces laterally. Protraction moves the mandible anteriorly, juts the jaw forward. Retraction returns the mandible to its original position. Elevation means lifting a body part superiorly. Depression means to move an elevated body part inferiorly. Opposition occurs when you touch your thumb to the fingers on the same hand.

Elbow Joint

The elbow joint provides a stable and smoothly operating hinge joint that allows flexion and extension only. The ligaments involved in providing stability to the elbow joint are the anular ligament, the ulnar collateral ligament, and the radial collateral ligament. Tendons of several arm muscles, the biceps and the triceps, also provide additional stability by crossing the elbow joint.

Hip (Coxal) Joint

The hip joint is a ball-and-socket joint that provides a good range of motion. Several strong ligaments reinforce the capsule of the hip joint. The muscle tendons that cross the joint contribute to the stability and strength of the joint, but the majority of the stability of the hip joint is due to the deep socket of the acetabulum and the ligaments.

Factors Influencing the Stability of Synovial Joints

The shapes of the articular surfaces of bones found at a synovial joint determine the movements that occur at the joint, but play a minimal role in stabilizing the joint. Ligaments at a synovial joint prevent excessive or unwanted movements and help to stabilize the joint; the greater the number of ligaments at the joint, the greater the stability. Muscle tone keeps tendons crossing joints taut, which is the most important factor stabilizing joints.

Temporomandibular Joint

The temporomandibular joint allows both hingelike movement and side-to-side lateral excursion. The joint contains an articular disc that divides the synovial cavity into compartments that support each type of movement. The lateral aspect of the fibrous capsule contains a lateral ligament that reinforces the joint.

Rotation

Turning of a bone along its own long axis. Medial rotation moves towards the midline of the body while lateral rotation is the opposite.