Anatomy of bones and joints

Joint stability refers to the resistance offered by various musculoskeletal tissues that surround a skeletal joint. Several structures influence the stability of a joint: • Shape of articulating surfaces • Fibrous capsule & ligaments • Muscles

• Joints have a rich blood & nerve supply • Common around joints: anastomoses (branching of vessels) • Hilton’s law: The nerve supplying a muscle that crosses a certain joint, also innervates this joint.

• Trauma • Arthritis – pain in joints linked to inflammation, osteoarthritis (defect in cartilage making movement difficult) and rheumatoid arthritis (autoimmune disorder) • Craniosynostosis – premature closing of cranial sutures, leading to abnormal deformed skull growth, which can affect brain development and trap nerves etc

• Standing upright • Head facing forward (anteriorly) • Upper limbs by sides, palms facing anteriorly, fingers together • Lower limbs straight, heels together, toes directed anteriorly • In males: erected penis • Anatomical position important as a common reference point

• Union between two or more rigid components (bone or cartilage) • Area of articulation • Joints are needed for movement and growth

Chondrocytes

Start on the inside and proceed to the outside: • Bones & articulating surfaces (hyaline cartilage from chondrocytes) • Synovial membrane • Intracapsular structures - discs, menisci, etc. • Capsule • Extracapsular structures - bursae • Stabilizing ligaments • Nerve and Arterial supply • Movements permitted & Muscles

Hinge - elbow Ball and socket - hip joint Pivot - atlantoaxial joint Saddle - between metacarpal and trapezium Condylar (ellipsoid) - knuckle Plane - acromioclavicular joint

Hinge – uniaxial, only permits flexion and extension e.g. elbow joint

Ball and socket – multiaxial, permits movements in several axes (flexion/extension, abduction/adduction, medial/lateral rotation, circumduction). Round head fitted into a cavity e.g. hip joint

Pivot – uniaxial, allows rotation. A round process of bone fits into a bony ligamentous socket e.g. atlantoaxial joint between atlas (C1) and axis (C2)

Saddle – biaxial, shaped like a saddle, concave and convex, found where bones are articulated e.g. between first metacarpal and trapezium of hand

Condylar (ellipsoid) – biaxial, permits wider range of flexion and extension, and a narrower range of abduction, adduction, and circumduction e.g. metacarpophalangeal (knuckle) joints

Plane – permits gliding and sliding movements e.g. acromioclavicular joint

The metaphysis is the wide portion of a long bone between the epiphysis and the narrow diaphysis. Is part of the growth plate in growing bones.

Condyle - articular facet, smooth end of a bone covered with cartilage that articulates in a joint with the condyle of and adjoining bone.

Epicondyle & Supracondylar region/ridge/line - protruding area above or below the condyle for attachment of ligaments and muscles that act on the joint.

Fossa (fossi pl.): a shallow depression

Process: Any projection or bump

Foramen (foramena): A rounded aperture for vessels and nerves, holes and bumps

Sulcus: A narrow groove

Tuberosity: A rough projection

Tubercle: A small rounded projection

Spine: A pointed process, allows attachment of muscle