Articulating Surfaces

Question 1

Describe the articular surfaces of the humero-ulnar joint

Answer 1

Humerus

• Trochlea = concave from side to side but convex from front to back
• Medial side of trochlea descends further down than lateral side
• Covered in hyaline cartilage

Ulna

• Trochlear notch has rounded, curved longitudinal ridge; extending from tip of olecranon to tip of coronoid process (fits groove of trochlea)
• covered in hyaline cartilage

Question 2

Describe the articular surfaces of the humero-radial joint

Answer 2

Humerus

• Capitulum = bony hemisphere on anterior inferior surface of distal humerus
• Covered with hyaline cartilage

Radius

• Head = concave with continuous convex cartilage around the sides (thickest in centre of concavity)
• Covered in hyaline cartilage
• annular ligament wraps around radial head to deepen articulation

Question 3

Describe the articulating surfaces of the superior radio-ulnar joint

Answer 3

Radial head

• Convex + circular
• Covered in hyaline cartilage

Ulna

• Radial fossa = concave
• Only articulates with 1/5 of radial head so annular ligament holds it in place

Question 4

Describe the articular surfaces of the inferior radio-ulnar joint

Answer 4

Ulnar head

• Convex, crescent shaped
• covered in hyaline cartilage

Radius

• Concave Ulnar notch
• covered in hyaline cartilage
• fibrocartilaginous ligament (triangular fibrocartilaginous articular disc) holds ulna and radius together
• attaches from lateral ulna styloid process to inferior margin of ulnar notch on radius