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 (skull).

Amphiarthrosis: a slightly movable joint (pelvis).

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.

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.

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 periodonatalligament. 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 hyalinecartilage. An example is the epiphyseal plate that connectsthe epiphysis and diaphysis of a growing bone. Anotherexample is the joint between the first rib and manubrium ofthe sternum.

Symphyses: here the ends of the articulating bones arecovered with hyaline cartilage but the bones are connected bya broad flat disc of fibrocartilage. Examples: pubicsymphysis, 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 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).

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.

Types of Synovial Joints Condyloid Joints-also called ellipsoidal joint. The convex oval-

shaped projection of one fits into the oval-shaped depression ofanother. Eg. Wrist and metacarpophalangeal joints. Biaxial.

Saddle Joints-here the articular surface of one bone issaddle-shaped and the articular surface of the other fitsinto the “saddle”. Eg. Carpometacarpal joint. Biaxial.

Ball-and-Socket Joints- this consists of the ball-likesurface of one bone fitting into a cuplike depression ofanother 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.

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

Range of motion (ROM)Refers to the range, measured in degrees of a circle, through which the bones of a joint can be moved

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.