JOINTS

Chapter 9

Arthrology

• Bones are too rigid to bend. Flexible connective tissues from joints and permit movement.

• A joint, also called articulation is a point of contact.

• The scientific study of joints is called arthrology.• The study of the motion of the human body is

called kinesiology.

Joint Classification

• Structurally joints are classified as following:– Fibrous joints : the bones are held together by

fibrous connective tissue that is rich in collagen fibers. No synovial cavity.

– Cartilaginous joints: the bones are held together by cartilage. No synovial cavity.

– Synovial joints: the bones forming the joint have a synovial cavity and are united by dense irregular connective tissue.

Joint Classification

• Functionally, joints are classified as one of the following:– Synarthrosis: an immovable joint.– Amphiarthrosis: a slightly movable joint.– Diarthrosis: a freely movable joint. All

diarthroses are synovial joints.

Fibrous Joints

• These are joints that lack a synovial cavity. They permit little or no movement.– Sutures: thin layer of dense connective issue.

Unites bones of the skull. Because a suture is immovable, it is functionally classified as a synarthrosis. Some sutures are replaced by bone in the adult. Such a suture is called synostosis.

Fibrous Joints

– Syndesmoses: there is a greater distance between the bones and more fibrous connective tissue. The tissue is either arranged as a bundle (ligament) or as a sheet (interosseus membrane). Example tibia/fibula. Because it permits slight movement, a syndesmosis is classified functionally as an amphiarthrosis.

Fibrous Joints

• Gomphoses- this is a type of fibrous joint in which a cone-shaped peg fits into a socket. The only example are the articulations of the roots of the teeth with the sockets of the alveolar processes of the maxillae and mandible. The dense fibrous connective tissue is called the periodonatal ligament. This is functionally classified as a synarthrosis.

Cartilaginous Joints

• This also lacks a synovial cavity and permits little or no movement.– Synchondroses: here the connecting material is

hyaline cartilage. An example is the epiphyseal plate that connects the epiphysis and diaphysis of a growing bone. Another example is the joint between the first rib and manubrium of the sternum.

Cartilaginous Joints

• Symphyses: here the ends of the articulating bones are covered with hyaline cartilage but the bones are connected by a broad flat disc of fibrocartilage. Examples: pubic symphysis, junction of the manubrium and sternum, intervertebral joints. Functionally, this is an amphiarthrosis, a slightly movable joint.

Synovial Joints

• These have a space called a synovial cavity between the articulating bones. Classified functionally as diarthroses.– The bones at synovial joint are covered by an

articular cartilage. Consists of two layers, an outer fibrous capsule and an inner synovial membrane.

– Fibrous capsule-ligaments– Synovial membrane-areolar connective tissue with

elastic fibers. Adipose tissue-articular fat pads.

Synovial Joints

• Synovial fluid: the synovial membrane secretes this. Consists of hyaluronic acid and interstitial fluid filtered from blood plasma. Reduces friction by lubricating the joint. Supplies nutrients and removes metabolic wastes. Contains phagocytic cells. Benefits of a “warm up” before exercise is that it stimulates the production and secretion of synovial fluid.

Synovial Joints

• Accessory ligaments and articular discs:• Nerve and Blood Supply: contain many nerve

endings. Convey information to the brain and spinal cord. Arteries penetrate the ligaments and articular capsule to deliver oxygen and nutrients. Veins remove carbon dioxide and wastes from the joints. The articulating portions receive nourishment from the fluid. Rest by blood capillaries.

Types of Synovial Joints

• Planar joints- the articulating surfaces are flat or slightly curved. Example are intercarpal joints, intertarsal joints, sternoclavicular joints, acromioclavicular joints, sternocostal joints, vertebrocostal joints.

• Hinge Joints-the convex surface of one fits into the concave surface of another. Eg. Knee, elbow, ankle, interphalangeal. Monaxial (uniaxial).

Types of Synovial Joints

• Pivot Joints-here the rounded or pointed surface of one bone articulates with a ring formed partly by another bone and partly by a ligament. This is monaxial. Examples atlanto-axial joint, radioulnar joint:turns palm anteriorly and posteriorly.

• Condyloid Joints-also called ellipsoidal joint. The convex oval-shaped projection of one fits into the oval-shaped depression of another. Eg. Wrist and metacarpophalangeal joints. Biaxial.

Types of Synovial Joints

• Saddle Joints-here the articular surface of one bone is saddle-shaped and the articular surface of the other fits into the “saddle”. Eg. Carpometacarpal joint. Biaxial.

• Ball-and-Socket Joints- this consists of the ball-like surface of one bone fitting into a cuplike depression of another bone. Egs. Shoulder and hip joints. Multiaxial.

Bursae and Tendon Sheaths

• Bursae: saclike structures that reduce friction. Located in the shoulder and knee joints. Found between skin and bone, tendons and bones, muscles and bones, ligaments and bones.

• Tendon Sheaths: tubelike bursae that wrap around tendons. Found at the wrist, ankle, fingers and toes.

Types of Movements

• Gliding:this consists of side-to-side and back-and-forth movements.

• Angular movements: there is an increase or decrease in the angle between articulating movements. Includes flexion, extension, lateral flexion, hyperextension.

Types of Movements

• Abduction: this is the movement of a bone away from the midline.

• Adduction: this is the movement of bone toward the midline.

• Circumduction: this is the movement of the distal end of a body part in a circle.

Types of Movements

• Rotation: a bone revolves around its own longitudinal axis. Pivot and ball-and-socket joints permit rotation. Medial (internal) rotation and lateral (external) rotation.

• Special movements: elevation, depression, protraction, retraction, inversion, eversion, dorsiflexion, plantar flexion, supination, pronation, opposition.

Factors affecting ROM at Synovial Joints

• Structure or shape of the articulating bones• Strength and tension of ligaments.• Arrangement and tension of muscles• Apposition of soft parts• Hormones• Disuse

Aging and Joints

• Decreased production of synovial fluid• Articular cartilage becomes thinner with

age, ligaments shortens and lose flexibility.• Genetic factors• Males commonly develop degenerative

changes in the vertebral column-hunched.• Osteoarthritis-occurs over age 70.