Joints of the Human Body PDF

Joints of the Human Body Siobhán O’Connor MSc PhD Certified Athletic Therapist (CAT) Joint (arthroses or articulation) • is the joining between two or more bones and can be movable or immovable. • Bones are two rigid to bend without being damaged so we have joints • When we say a bone articulates...

Joints of the Human Body Siobhán O’Connor MSc PhD Certified Athletic Therapist (CAT) Joint (arthroses or articulation) • is the joining between two or more bones and can be movable or immovable. • Bones are two rigid to bend without being damaged so we have joints • When we say a bone articulates with another bone, we mean the bones form a joint Types • Classified into types depending on their general morphology • Held together by fibrous tissue (and ligaments) that provide stability Simple • Only 2 articulating surfaces e.g. elbow Compound • 3+ articulating surfaces e.g. wrist Complex • 2+ surfaces and articular/fibrocartilage disc e.g. knee/vertebrae Joint Position • Close-packed - Max contact - Best fit - Most stable e.g. foot supination • Loose-packed - Min contact - Less stable e.g. foot pronated Joint Type 3 types of joints – Fibrous (synarthrosis) Movement - Little or none e.g. Skull sutures – Cartilaginous (amphiarthrosis) Movement - Limited – e.g. pubic symphysis, vertebrae - Synovial (diarthrosis) Movement – Large ROM – e.g. knee There is a synovial cavity • Fibrous joints – are found between two bones connected by fibrous tissue (collagen) • There are 3 different types of fibrous joint: – sutures (skull) – gomphoses (teeth) – syndesmosis (interosseous membrane) Fibrous Joint Cartilaginous joint • are two bones connected by a pad of cartilage • fibrocartilage or hyaline cartilage There are 2 types of cartilaginous joints: • Synchondroses (Primary) • Two bones are joined by hyaline cartilage. • With age these joints change into a synostosis as they ossify to become a continuous bone. e.g. epiphyseal plate • Symphyses (Secondary) • two bones which are covered in hyaline cartilage are joined together by a fibrocartilage disc. (allow a small amount of controlled movement) e.g. intervertebral disc and pubic symphysis Synovial joints • are movable joints and have a large range of motion • Hyaline cartilage and the synovial fluid • allows the bone surfaces to slide over each other relatively free from friction. • Fibrous joint capsule • Around the joint • This attaches to the articular margins of the adjacent bones • Lined by synovial membrane • Creates a cavity between the connecting bones which is filled with synovial fluid • Ligaments • Thickened parts of capsule • with the surrounding muscles hold the bones in position. Synovial (Diarthrosis) Synovial Joints • Typical bone ends are covered with Hyaline cartilage • Atypical bone ends covered with fibrocartilage e.g TMJ / sternoclavicular / sacroiliac • Consists of hyaluronic acid and interstitial fluid (filtered plasma) • Reduces friction by lubricating joint • Supplies nutrients to and removes waste from cartilage (diffusion) • Contains phagocytic cells • immune cells that play an important role in our immune response and ingest & destroy both microbes & cellular debris Synovial fluid Synovial Joint - Hinge Example. - Elbow joint (humeroulnar part) interphalangeal • A joint in which a convex surface joins with a concave surface Uniaxial - one plane • movement is restricted to one plane by the shape of the opposing articular surfaces as well as the strong collateral ligaments along the sides of the joint. • like the hinge on a door. • Generally, flexion and extension Example • Between the articular processes of the vertebrae • Carpals, tarsals Uniaxial • their articular surfaces are flat and glide over each other. Synovial Joint Gliding Synovial joint - Pivot Example • Radioulnar joint (sup. and inf.) • Skull and vertebrae • The atlas (C1) pivots around the dens of the axis (C2). • consists of a bony pivot (projection) within an osteoligamentous ring. Uniaxial Example • Only one in body • Carpometacarpal joint of the thumb (between the trapezium and the first metacarpal). Biaxial • with both bones possessing concavo-convex surfaces; • each surface is concave in one direction and convex in the other direction. • Many movements except rotation Synovial joint Saddle Synovial joint - Condyloid Examples • Knuckles • Metacarpophalangeal joints - joint between metacarpals and phalanges • Radiocarpal joint in wrist Biaxial • Flexion, extension, abduction, adduction, circumduction. • Oval shaped projection fits into an oval shaped depression Synovial Joint – Ball and Socket Example • Hip joint. • Shoulder joint Multiaxial • most flexible joints in the body. • Consist of a hemispherical head (ball like surface) that fits into a cup-like depression. • Flexion, extension, abduction, adduction, circumduction, rotation Capsule • Sleevelike articular capsule surrounds a synovial joint • It encloses the synovial cavity & unites the articulating bones. Accessory Ligaments • Help stabilise the joint • Extracapsular • Lie outside the articular capsule • E.g. medial collateral ligament (MCL) • Intracapsular • Lie inside the articular capsule • E.g. anterior cruciate ligament (ACL) Articular Discs • Some synovial joints (e.g. knee) have pads of fibro-cartilage lying between the articular surfaces of the bones & are attached to the capsule. • E.g. medial and later menisci (meniscus is singular) in the knee • E.g. Articular disk in the Sternoclavicular joint • Allow two bones of different shapes fit together more tightly, maintain stability of the joint & direct the flow of synovial fluid to areas of greatest friction • Friction can occur • Bursae (bursa singular) Bursae • Saclike structures strategically situated to alleviate friction in some joints (e.g. shoulder & knee joints)