Chapter 8 Joints - Lecture notes 8 PDF

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William Rose...

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Chapter 8 Joints

Joints (Articulations) -

Weakest parts of the skeleton Articulation o Site where two or more bones meet Functions of joints o Give the skeleton mobility o Hold the skeleton together

Classfication of Joints: Structural -

Structural classification focuses on the material binding bones together and whether or not a joint cavity is present The 3 structural classification are o Fibrous o Cartilaginous o Synovial

Classification of Joints: Functional -

Functional classification is based on the amount of movement allowed by the joint The 3 functional classes of joints are o Synarthroses  Immovable o Amphiarthroses  Slightly moveable o Diarthroses  Freely movable

Fibrous Structural Joints -

The bones are joined by fibrous tissues There is no joint cavity Most are immovable There are 3 types o Sutures o Syndesmoses o Gomphoses

Fibrous structural joints: sutures -

Occur between the bones of the skull Comprised of interlocking junctions completely filled with connective tissue fibers Bind bones tightly together, but allow for growth during youth In middle age, skull bones fuse and are called synostoses

Fibrous structural joints: Syndesmoses -

Bones are connected by a fibrous tissue ligament Movement varies from immovable to slightly variable Examples include the connection between the tibia and fibula, and the radius and ulna

Fibrous structural joints: Gomphoses -

The peg-in-socket fibrous joint between a tooth and its alveolar socket The fibrous connection is the periodontal ligament

Cartilaginous Joints -

Articulating bones are united by cartilage Lack a joint cavity Two types o Synchondroses o Symphyses

Cartilaginous Joints: Synchondroses -

A bar or plate of hyaline cartilage unites the bones All synchondroses are synarthrotic Examples include o Epiphyseal plates of children o Joint between the costal cartilage of the first rib and the sternum

Cartilaginous Joints: Symphyses -

Hyaline cartilage covers the articulating surface of the bone and is fused to an intervening pad of fibrocartilage Amphiarthrotic joints designed for strength and flexibility Examples include intervertebral joints and the pubic symphysis of the pelvis

Synovial Joints -

Those joints in which the articulating bones are separated by a fluid-containing joint cavity All are freely movable diarthroses Examples – all limb joints, and most joints of the body

Synovial Joints: General Structure 

Synovial joints all have the following 

Articular cartilage

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Joint (synovial) cavity

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Articular capsule

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Synovial fluid

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Reinforcing ligaments

Synovial Joints: Friction-Reducing Structures 

Bursae – flattened, fibrous sacs lined with synovial membranes and containing synovial fluid

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Common where ligaments, muscles, skin, tendons, or bones rub together

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Tendon sheath – elongated bursa that wraps completely around a tendon

Synovial Joints: Stability 

Stability is determined by: 

Articular surfaces – shape determines what movements are possible

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Ligaments – unite bones and prevent excessive or undesirable motion

Synovial Joints: Stability 

Muscle tone is accomplished by: 

Muscle tendons across joints acting as stabilizing factors

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Tendons that are kept tight at all times by muscle tone

Synovial Joints: Movement 

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The two muscle attachments across a joint are: 

Origin – attachment to the immovable bone

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Insertion – attachment to the movable bone

Described as movement along transverse, frontal, or sagittal planes

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The two muscle attachments across a joint are: 

Origin – attachment to the immovable bone

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Insertion – attachment to the movable bone

Described as movement along transverse, frontal, or sagittal planes

Synovial Joints: Range of Motion 

Nonaxial – slipping movements only

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Uniaxial – movement in one plane

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Biaxial – movement in two planes

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Multiaxial – movement in or around all three planes

Gliding Movements 

One flat bone surface glides or slips over another similar surface

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Examples – intercarpal and intertarsal joints, and between the flat articular processes of the vertebrae

Angular Movement 

Flexion — bending movement that decreases the angle of the joint

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Extension — reverse of flexion; joint angle is increased

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Dorsiflexion and plantar flexion — up and down movement of the foot

Angular Movement 

Abduction — movement away from the midline

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Adduction — movement toward the midline

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Circumduction — movement describes a cone in space

Special Movements 

Supination and pronation

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Inversion and eversion

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Protraction and retraction

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Elevation and depression

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Opposition

Varus and Valgus 

Describe alignment of two segments in the frontal (coronal) plane.

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Varus alignment: distal segment deviates medially relative to proximal segment. Valgus alignment: distal segment deviates laterally relative to proximal segment. Varus, valgus often used to describe alignment at knee and ankle. Valgus at the knee: “knock-kneed” Varus at the knee: “bow-legged” Bunion: hallux valgus

Talocrural Joint -

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Ankle Joint (talus to lower leg = crural region) Ankle sprain – most common joint injury Low ankle sprain: tear of ligaments “below the ankle” o Inversion sprain – more common – damage to lateral ligaments (ant. & post. talofibular, calcaneofibular) o Eversion – damage to medial (deltoid) ligament High ankle sprain: tear of ligaments “above the ankle” o Tear of syndesmotic ligaments of distal tibiofibular joint (tibiofibular joints are syndesmotic, a subset of fibrous, and amphiarthrotic, i,.e. slightly movable.) o High ankle sprain generally takes longer to heal.

Protraction and Retraction -

Protraction o Moving the lower jaw forward or bringing it out Retraction o Moving the lower jaw backward...