Synovial Joints and Their Characteristics

Classification of Synovial Joints by Shape

• Gliding/Planar Joints

• Description: Flattened or slightly curved faces.

• Motion: Limited motion - nonaxial.

• Examples:

  • AC joint

  • Claviculosternal joint

  • SI joint

  • Vertebrocostal joints

  • Intercarpal/intertarsal joints

• Hinge Joints

• Description: Allow angular motion in a single plane (monaxial).

• Examples:

  • Ankle joint

  • Knee joint

  • Elbow joint

  • Interphalangeal joints

• Pivot Joints

• Description: Allow rotation only (monaxial).

• Examples:

  • Atlas (C1) on Axis (C2) joint

  • Proximal radioulnar joint

• Condylar (Ellipsoid) Joints

• Description: Oval articular face within a depression.

• Movement: Biaxial movement.

• Examples:

  • Radiocarpal joint

  • MCP joints 2-5

  • MTP joints

• Saddle Joints

• Description: Each articular face is concave along one axis and convex along the other.

• Motion: Permits angular movement while inhibiting rotation (biaxial).

• Example: First carpometacarpal joint (thumb joint).

• Ball-and-Socket Joints

• Description: Round articular face in a depression.

• Movement: Triaxial, allows for circumduction.

• Examples:

  • Hip joint

  • Shoulder joint

Intervertebral Articulations

• C1 to C2 Articulation:

• Joint type: Pivot joint

• Note: No disc allows rotation.

• C2 to L5 Spinal Vertebrae Articulation:

• Structure: Inferior and superior articular processes form diarthrotic gliding joints.

• Adjacent vertebral bodies: Amphiarthrotic symphyseal joints.

• Sacrum and coccyx segments are fused with no discs or symphyseal joints.

Intervertebral Discs (IVDs)

• IVDs Structure:

• Composed of fibrocartilage.

• Contains:

  • Anulus fibrosus (outer layer, circular fiber arrangement)

  • Nucleus pulposus (inner gel-like core)

• Damage to IVDs:

• Herniated Disc: Also known as "slipped disc", occurs when the nucleus pulposus displaces and may compress spinal nerves.

Intervertebral Ligaments

• Functions: Bind vertebrae together and stabilize the vertebral column.

• Key Ligaments:

1. Anterior longitudinal ligament: Connects anterior vertebral bodies.

2. Posterior longitudinal ligament: Connects posterior vertebral bodies.

3. Ligamentum flavum: Connects laminae.

4. Interspinous ligament: Connects spinous processes of adjacent vertebrae.

5. Supraspinous ligament: Connects the tips of spinous processes from C7 to sacrum.

6. Ligamentum Nuchae: Continuation of supraspinous ligament from C7 to the base of the skull.

Shoulder Joint (Glenohumeral Joint)

• Characteristics:

• Highest mobility → least stable joint.

• Supported by skeletal muscles, tendons, and ligaments.

• Joint type: Ball-and-socket diarthrosis.

• Glenoid Labrum: Deepens socket of the glenoid cavity and provides a fibrocartilage lining that extends beyond the bone.

• Accessory Structures:

• Ligaments:

  • Acromioclavicular ligament

  • Coracoacromial ligament

  • Coracoclavicular ligament

  • Coracohumeral ligament (cut)

  • Glenohumeral ligaments

• Muscles: Supraspinatus, infraspinatus, teres minor, subscapularis.

• Bursa: Subcoracoid, subacromial, and subdeltoid bursae.

Elbow Joint

• Joint type: Diarthrotic hinge joint consisting of three articulations:

• Humeroulnar joint: Largest articulation - trochlea of humerus and trochlear notch of ulna (limited movement).

• Humeroradial joint: Smaller articulation - capitulum of humerus and head of radius.

• Accessory Structures:

• Biceps brachii muscle: Attached to radial tuberosity.

• Key Ligaments:

  • Radial collateral ligament

  • Annular ligament

  • Ulnar collateral ligament

Hip Joint (Coxal Joint)

• Joint type: Diarthrotic ball-and-socket joint.

• Fibrocartilage Acetabular Labrum: Enhances stability and depth of the socket.

• Key Ligaments include:

• Iliofemoral ligament

• Pubofemoral ligament

• Ischiofemoral ligament

Knee Joint

• Joint type: Diarthrotic hinge joint that transfers weight from femur to tibia.

• Articulations:

• 2 femur-tibia articulations at medial and lateral condyles.

• 1 between patella & patellar surface of femur.

• Medial and Lateral Menisci: Fibrocartilage pads that cushion and stabilize the joint, providing lateral support.

Additional Information

• Autoimmune diseases and degenerative joint diseases (DJD) may be affected by diet high in uric acid (related to conditions like gout).

• Muscles associated with lower limbs include:

1. Gluteus medius

2. Sartorius

3. Fibularis longus

4. Rectus femoris

5. Pectineus

• Additional muscles: Soleus, tibialis anterior, gastrocnemius.