Joints (lecture 3) Flashcards
Joints
Regions of the skeleton where bones meet
and articulate with each other:
• Supported by a variety of soft tissues
• Function is either to allow movement or
growth
• There is no single best way to classify joints
but classification is usually based on either the
degree of movement possible or the nature of
the soft tissues involved
Classifications
• Fibrous – Bones are only separated by connective tissue with negligible movement • Cartilage – Primary cartilaginous (Synchondrosis) – Secondary cartilaginous (Symphysis) • Synovial – Characterized by 6 criteria
Fibrous joints
• Sutures – Immovable – Dense irregular connective tissue between bones • Syndesmosis – Slight movement – Greater distance – More connective tissue • Gomphosis - Teeth • Interosseous membrane
Cartilaginous joints
• Synchondrosis: – Bone and hyaline cartilage meet – Immobile – Very strong – Epiphyseal growth plate • Symphysis: 1. Articular surfaces lined with hyaline cartilage with a fibrocartilage disc in between 2. Limited amount of movement 3. Pubic symphysis
Synovial joints
• Articular surfaces covered with hyaline cartilage • Has a joint cavity • Has a joint capsule • Has a synovial membrane • Reinforced by ligaments internally, externally or both • Capable of varying degrees of movement
Synovial Joint Movements
• Gliding – Flat bone surfaces – Limited in range – No significant alteration in angle • Angular – Change in angle – Described in terms of the body planes – Flexion – Extension – Abduction – Adduction – Lateral flexion, Hyperextension, Circumduction
c
Rotations:
– A bone revolves around its own longitudinal axis
– Usually requires “fixing” another joint before rotation
can be achieved
– At limbs this is defined in relation to the midline
– Medial / internal rotation
– Lateral / external rotation
Synovial Joint Movements
Special movements:
Elevation – Depression – Protraction – Retraction – Inversion – Eversion – Dorsiflexion – Plantarflexion – Supination – Pronation – Opposition
Temporomandibular Joint
• Classification – Atypical Synovial joint – Modified hinge/ condylar • Articular surfaces: – Condyle of the mandible – (Anterior) Articular tubercle of temporal bone – Mandibular fossa
What makes the TMJ unique?
• Articular surfaces not covered with Hyaline cartilage
Glenohumeral Joint
• Articulation between – Head of humerus & glenoid cavity • Highly mobile at expense of stability • Factors increasing stability – Bony arch – Rotator cuff – Ligaments both intra- and extracapsular
Dislocation
• Prevented by: – Bony arch – superior – Ligaments – anterior and posterior – Biceps long head tendon – Rotator cuff muscles – mainly during movement • Shoulder joint is weakest inferiorly • Dislocation usually happens infero-anteriorly in the absence of fracture • Very painful • Once dislocated can reoccur
Hip joint
• More stable than shoulder and somewhat less mobile • Weight bearing joint • Femur neck fractures often in elderly – Osteoporosis – Can be devastating
Age related changes
• Decreased production of synovial fluid • Articular cartilage becomes thinner • Mainly on weight bearing joints – Knees and hips • Osteoarthritis
Replacements
Interesting bit: Metal and ceramic replacements carry unique serial numbers that can be
traced to manufacturer and is registered to the individual – can be used in identification
