Joints

Joint (AKA Articulation)

A point of contact between bones, between cartilage and bone or between teeth and bone

More Definitions

Arthrology – The study of joints

Kinesiology – study of the movement of the human body

Rheumatology – the field of medicine devoted to joint diseases and related conditions

Classification of Joints

Structural Classification – classified by the presence or absence of space between bones and the type of connective tissue that binds them together

Functional Classification – related to the degree of movement it permits

Structural Classifications

Fibrous Joints

Cartilaginous Joints

Synovial Joints

Functional Classifications

Synarthrosis – immovable joint

Amphiarthrosis – slightly moveable joint

Diarthrosis – Freely movable joint

Fibrous Joints

Bones are held together by fibrous connective tissue that is rich in collagen fibers

No synovial cavity

Fibrous joints

Permits little or no movement

Suture – connect bones of the skull

Syndesmosis – the distance between the 2 bones is greater than in a suture. Ex – between tibia and fibula

Gomphosis – a cone shaped peg (tooth) fits into a cavity (socket)

Cartilaginous Joints

The bones are held together by cartilage

No synovial cavity

Cartilaginous Joints

Allows little or no movement

Synchondrosis – the connecting material is hyaline cartilage. Ex - epiphyseal plate

Symphysis – ends of the bones are covered with articular cartilage but the cones are connected by a broad flat disc of fibrocartilage. Ex – pubic symphysis

Synovial Joints

Bones have a synovial cavity and are united by a dense irregular connective tissue and accessory ligaments

Synovial joints

Unique Characteristics:Synovial cavityArticular cartilageArticular capsule

Fibrous capsule – outer layer (can form ligaments)Synovial membrane – areolar connective tissue with

elastic fibersSynovial Fluid – secreted by the synovial

membrane. It lubricates the joint, supplies nutrients and removes metabolic waste.

Synovial joints

Accessory Ligaments – ligaments that are both inside and outside the articular capsule (ex – collateral ligaments of the knee)

Menisci – pads of fibrocartilage that lie between articular surfaces of the bones and attach to the fibrous capsule

Allows 2 bones of different shapes to fit more tightlyBursa – saclike structures between skin and

bone or between tendons and bones situated to reduce friction

Torn Meniscus

The tearing of the cartilage in the knee is common among athletes. Damaged cartilage can wear away the joint and eventually develop into arthritis. The surgical repair of the knee may be assisted by arthroscopy (a small lighted tool is inserted into the knee for visualization)

Types of Synovial Joints

Planar – intercarpal, intertarsal, sternoclavicular

Hinge – knee, elbow, ankle, fingers

Pivot – atlanoaxial, radioulnar

Condyloid – wrist and metacarpals

Saddle – wrist and thumb

Ball and Socket – shoulder, hips

SEE ALSO PAGE 163 IN THE TEXT BOOK FOR VERY GOOD ILLUSTRATIONS OF THE SYNOVIAL JOINTS