Anatomy of Joints

Anatomy of Joints

• Presented by Dr. Sayed Jahin, lecturer of anatomy and embryology
• Joints connect bones, allowing movement.

How Bones Connect

• Ligaments: Tough bands of fibrous, slightly elastic tissue, connecting bone ends, preventing dislocation and excessive movement. Fractures can result from extreme movements
• Joints: Areas where two or more bones meet, enabling movements.

Joints - Definition and Functions

• Definition: Also called Articulations, the point where two or more bones connect.
• Functions:
  • Hold the skeletal system together
  • Enable flexibility in the skeleton
  • Aid in bone growth

Classification of Joints

• Functional Classification: Based on the degree of movement:
  • Synarthroses: Immovable joints
  • Amphiarthroses: Slightly movable joints
  • Diarthroses: Freely movable joints
• Structural Classification: Based on how bones connect:
  • Fibrous Joints: Generally immovable
  • Cartilaginous Joints: Immovable or slightly movable
  • Synovial Joints: Freely movable

Fibrous Joints

• Bones are joined by fibrous tissue (dense connective tissue), mainly collagen.
• Fixed (immovable) joints.
• Types of Fibrous Joints:
  • Sutures (e.g., skull sutures)
  • Syndesmoses (e.g., inferior tibiofibular joint)
  • Gomphoses (e.g., tooth in jaw socket)

Sutures

• Bones are tightly bound by a minimal amount of fibrous tissue called sutures.
• Located between the bones of the skull.

Syndesmoses

• Bones connected exclusively by ligaments or membranes.
• Movement depends on the length of the fibers.
• Example: Tibiofibular joint

Gomphoses

• Specialized fibrous joints restricting tooth placement in the alveolar sockets of the jawbones.
• Tooth root attached to socket by periodontal ligament.

Cartilaginous Joints

• Cartilage is a smooth, elastic, rubber-like tissue.
• Used in rib cage, ears, nose, bronchial tubes, intervertebral discs, and other body parts.
• Types of Cartilage:
  • Hyaline
  • Fibrocartilage
  • Elastic cartilage

1-Primary Cartilaginous Joints

• Temporary joints that disappear with age via ossification (bone growth).
• Immobile joints, consisting of a plate of hyaline cartilage.
• Examples:
  • Between the first rib and sternum (first sternocostal joint).
  • Between epiphysis and diaphysis of bones.
  • Rib to costal cartilage junctions.

2-Secondary Cartilaginous Joints

• Permanent joints found in the midline.
• Limited mobility.
• Articulating bone surfaces covered by hyaline cartilage, separated by fibrocartilaginous discs.
• Examples:
  • Intervertebral discs
  • Symphysis pubis

3- Synovial Joints

• Most mobile type of joint.
• Features:
  • Articular surfaces covered in hyaline cartilage for smooth movement.
  • Joint cavity filled with synovial fluid: Lubricates and nourishes articulating cartilage.
  • Articular capsule made of fibrous tissue lined with a synovial membrane.
  • Surrounded by ligaments and muscles for support

Types of Synovial Joints - 1 Hinge

• One bone is a convex cylinder, connecting with the concavity of another bone.
• Example: Elbow, ankles, interphalangeal joints, and knee (modified hinge).
• Axis of movement: Transverse axis (flexion and extension).

Types of Synovial Joints - 2 Ball and Socket

• Rounded head of one bone articulates with a socket of another.
• Example: Hip and shoulder.
• Produces wide range of movement: flexion/extension, abduction/adduction and rotation.

Types of Synovial Joints - 3 Plane (Gliding)

• Flat articular surfaces causing sliding movements.
• Example: Intracarpal and intratarsal joints.
• Moveable in flexion/extension, abduction/adduction

Types of Synovial Joints - 4 Pivot

• Rounded or conical surface of one bone fits into a ring of another bone.
• Example: Superior radio-ulnar joint.
• Only rotation movement.

Types of Synovial Joints - 5 Condylar

• Oval-shaped end of one bone fits into the oval cavity of another.
• Example: Wrist joint.
• Movements: flexion, extension, abduction, and adduction.

Types of Synovial Joints - 6 Saddle

• Saddle-shaped ends of bones that fit together.
• Example: Thumb joint.
• Allows extensive back-and-forth and up-and-down movement.

Stability of Synovial Joints

• Shape of articular surfaces: Ball and socket hip is a good example of how bone shape is important
• Strength of ligaments: Ligaments prevent excessive movement. Example: cruciate ligaments in knee.
• Tone of surrounding muscles: Maintains stability in most joints; example: shoulder muscles that keep shoulder head in glenoid cavity.

Summary of Questions and Answers (from the final image)

• Question 1: Knee joint type: Hinge
• Question 2: Most mobile joints: Synovial
• Question 3: Shoulder joint subtype: Ball and socket
• Question 4: Ankle joint subtype: Hinge
• Question 5: Ball and socket joint example: Hip (and potentially shoulder)
• Question 6: Intracarpal joints: Gliding
• Question 7: Only saddle joint example: Thumb