A joint (also called an articulation) is the site where two or more bones meet in the body. Joints allow for movement and provide mechanical support.
Key Points:
- Joints may
be movable (like the knee), partially movable (like the
spine), or immovable (like skull sutures).
- Joints are
classified based on:
- Structure:
fibrous, cartilaginous, synovial
- Function:
immovable (synarthrosis), slightly movable (amphiarthrosis), freely
movable (diarthrosis)
Simple Mnemonic for
Function:
"SAD"
- Synarthrosis
= Still (Immovable)
- Amphiarthrosis
= A little movement
- Diarthrosis
= Dancing joints (Freely movable)
Classification of Joints
Fibrous Joints
- Sutures
(Skull bones)
- Syndesmosis
(Inferior tibiofibular joint)
- Gomphosis
(Tooth and alveolar socket)
Cartilaginous Joints
- Primary
(Synchondrosis): e.g., First sternocostal joint
- Secondary
(Symphysis): e.g., Intervertebral discs, Pubic symphysis
Synovial Joints (See
details below)
Details of Synovial Joints
- Structure: Joint
cavity, synovial fluid, articular cartilage, capsule
- Types of
Synovial Joints & Examples:
- Plane
Joint – Acromioclavicular joint
- Hinge
Joint – Elbow, Knee, Ankle
- Pivot
Joint – Atlantoaxial joint (between C1 & C2
vertebrae)
- Condyloid
Joint – Wrist joint (radiocarpal)
- Saddle
Joint – 1st carpometacarpal joint (thumb)
- Ball and
Socket Joint – Shoulder, Hip
Movements of Synovial Joints
- Flexion/Extension – Elbow,
Knee
- Abduction/Adduction –
Shoulder, Hip, Fingers
- Rotation –
Atlantoaxial joint, Shoulder
- Circumduction –
Shoulder, Hip
- Special
Movements:
- Pronation/Supination –
Radioulnar joint
- Inversion/Eversion –
Subtalar joint (ankle)
- Opposition/Reposition – Thumb joint
Examples of Each Joint Type
- Fibrous: Sutures
of skull, inferior tibiofibular joint
- Cartilaginous:
- Primary:
Costochondral joints
- Secondary:
Pubic symphysis
- Synovial:
- Plane:
Intercarpal joints
- Hinge:
Elbow
- Pivot:
Proximal radioulnar joint
- Condyloid:
Metacarpophalangeal joints
- Saddle:
Thumb joint
- Ball & Socket: Shoulder, Hip
Differences Between Joint
Types
|
Feature |
Fibrous |
Cartilaginous |
Synovial |
|
Mobility |
Immovable/slight |
Slight |
Freely movable |
|
Cavity |
Absent |
Absent |
Present |
|
Example |
Sutures |
Pubic symphysis |
Elbow, Shoulder |
Clinical Correlations &
Conditions Related to Joints
- Osteoarthritis –
Degeneration of joint cartilage (common in knees, hips)
- Rheumatoid
arthritis – Autoimmune, affects small joints
- Dislocation –
Shoulder, jaw commonly affected
- Sprain –
Ligament injury in ankle, wrist
- Bursitis – Inflammation of bursa (e.g., prepatellar bursa = "housemaid’s knee")
Joint Stability and Factors
Affecting It
- Shape of
articular surfaces
- Ligaments –
Cruciate ligaments in knee
- Muscle
tone – Rotator cuff muscles stabilize shoulder joint
- Joint
capsule
- Atmospheric
pressure
- Accessory structures – Menisci in knee, labrum in shoulder/hip
Tags
ANATOMY