Lecture 9 cont Articulations and Joints

Structural Classification

• Structural criteria: presence of a joint cavity; type of connective tissue involved.

• Fibrous joints: no joint cavity; held by dense fibrous CT; little or no movement.

  • Examples: sutures, syndesmoses, interosseous membranes, gomphosis (teeth in sockets).

• Cartilaginous joints: no joint cavity; bones joined by cartilage; limited movement.

  • Examples: synchondroses (hyaline cartilage, e.g., epiphyseal plates, first sternocostal joint), symphyses (fibrocartilage, e.g., pubic symphysis, intervertebral joints).

• Synovial joints: have a synovial cavity; ends of long bones covered by articular cartilage; freely movable; surrounded by an articular capsule and ligaments.

  • Examples: hip, knee, shoulder, elbow, TMJ.

Functional Classification

• Synarthroses: no movement (e.g., sutures, gomphosis).

• Amphiarthroses: little movement (e.g., pubic symphysis, intervertebral discs).

• Diarthroses: freely movable (e.g., hip, knee, shoulder, elbow, TMJ).

Characteristic Features of Joint Types

Fibrous Joints

• Held together by fibrous connective tissue.

• No synovial cavity.

• Little to no movement.

• Examples:

  • Sutures: found in the skull, immovable.

  • Syndesmoses: bones connected by a ligament, slight movement (e.g., tibiofibular joint).

  • Interosseous membranes: broad sheet of fibrous CT connecting long bones (e.g., between radius and ulna).

  • Gomphosis: teeth in sockets, considered a type of fibrous joint with little or no movement.

Cartilaginous Joints

• Bones connected by cartilage.

• No joint cavity.

• Limited movement.

• Two main types:

  • Synchondroses: hyaline cartilage; temporary joints; allow no movement in mature individuals.

  • Examples: epiphyseal plates (temporary), first sternocostal joint.

  • Symphyses: fibrocartilage; allow slight movement (amphiarthroses).

  • Examples: pubic symphysis, intervertebral joints.

Synovial Joints

• Contain a synovial cavity, making them freely movable (diarthroses).

• Ends of bones covered with articular (hyaline) cartilage.

• Structure:

  • Articular cartilage: hyaline cartilage, reduces friction, absorbs shock.

  • Articular capsule: two layers:

  • Fibrous membrane: dense irregular CT, attaches to periosteum, may contain ligaments.

  • Synovial membrane: areolar tissue, lines the joint cavity except for articular cartilage; produces synovial fluid.

  • Synovial fluid: viscous, lubricates, cushions, nourishes articular cartilage, and removes waste.

  • Ligaments: reinforce the joint capsule, connecting bones.

• Features: well-vascularized and innervated; most joints in the body are synovial.

• Associated structures:

  • Bursae: sacs filled with synovial fluid; cushion movement between structures.

  • Tendon sheaths: elongated bursae surrounding tendons with high friction.

Body Movements at Synovial Joints

• Angular movements:

  • Flexion: decreases the angle between bones.

  • Extension: increases the angle between bones.

  • Abduction: movement away from the midline.

  • Adduction: movement toward the midline.

  • Circumduction: combination of flexion, extension, abduction, and adduction in a cone-like motion.

• Rotation: turning a bone around its own long axis.

  • Medial (internal) rotation: rotation toward the midline.

  • Lateral (external) rotation: rotation away from the midline.

• Special movements:

  • Pronation: forearm rotates medially, palm faces posteriorly.

  • Supination: forearm rotates laterally, palm faces anteriorly.

  • Dorsiflexion: lifting the foot superiorly toward the shin.

  • Plantar flexion: depressing the foot (pointing toes).

  • Inversion: sole of the foot turns medially.

  • Eversion: sole of the foot turns laterally.

  • Protraction: anterior movement of a body part.

  • Retraction: posterior movement of a body part.

  • Elevation: superior movement of a body part.

  • Depression: inferior movement of a body part.

  • Opposition: movement of the thumb to touch the tips of other fingers.

Types of Movement at Synovial Joints (based on axis and shape)

• Condyloid: biaxial (flex/extend; abduct/adduct; limited circumduction).

• Saddle: biaxial (similar movements as condyloid, but different articulation shape, e.g., carpometacarpal joint of the thumb).

• Ball-and-socket: multiaxial (flex/extend; abduct/adduct; rotation, e.g., hip, shoulder).

Structure and Movements of Specific Body Joints

• Temporomandibular Joint (TMJ):

  • Structure: Articulation between the temporal bone and the mandible; contains an articular disc.

  • Movements: Opening involves forward movement (protraction) and hinge action (depression); retraction, elevation, lateral deviation.

• Shoulder Joint (Glenohumeral):

  • Structure: Ball-and-socket joint between the head of the humerus and the glenoid cavity of the scapula; widest ROM; loose capsule; reinforced by ligaments and the rotator cuff muscles.

  • Movements: Flexion, extension, abduction, adduction, medial and lateral rotation, circumduction.

• Elbow Joint:

  • Structure: Synovial hinge joint primarily between the trochlea of the humerus and the trochlear notch of the ulna; includes the olecranon bursa; capsule and strong collateral ligaments.

  • Movements: Flexion and extension.

• Hip Joint:

  • Structure: Ball-and-socket joint between the head of the femur and the acetabulum of the pelvis; features an acetabular labrum (fibrocartilage rim) that deepens the socket; strong ligaments; robust articular capsule.

  • Movements: Flexion, extension, abduction, adduction, medial and lateral rotation, circumduction.

Joint Injuries and Disorders

• Sprains:

  • Description: Ligament injuries, caused by a joint forced beyond its normal range of motion.

  • Severity: Range from overstretching to complete tearing of the ligament.

  • Examples: Ankle sprain, ACL tear in the knee.

  • Treatment: RICE (Rest, Ice, Compression, Elevation) or physical therapy (PT).

• Strains:

  • Description: Tendon or muscle injuries due to overstretch or tear.

  • Examples: Pulled hamstring.

  • Treatment: Rest, ice, gentle stretching, PT.

• Bursitis:

  • Description: Inflammation of bursae.

  • Cause: Often due to overuse or direct trauma.

  • Symptoms: Pain, swelling, tenderness.

  • Locations: Common in shoulder, elbow (e.g., tennis elbow), hip, knee.

  • Treatment: Rest, ice, NSAIDs, corticosteroids.

• TMJ Disorders (TMJD):

  • Description: A set of conditions causing pain and dysfunction in the temporomandibular joint.

  • Causes: Often due to bruxism (teeth grinding), stress, trauma, jaw misalignment.

  • Symptoms: Pain in the jaw, head, and neck; clicking or popping sounds; limited jaw movement.

  • Location: Temporomandibular joint.

  • Treatment: Night guard, splint therapy, botox, disk realignment, stress management.

• Gout:

  • Description: A form of inflammatory arthritis.

  • Cause: Uric acid crystal deposition in joints, leading to a sudden, severe attack.

  • Symptoms: Intense joint pain, redness, swelling, warmth.

  • Location: Most commonly affects the big toe, but can occur in other joints.

  • Risk factors: Diet (high purine foods), dehydration, genetics.

  • Treatment: NSAIDs, lifestyle changes (diet, hydration).

• Osteoarthritis (OA):

  • Description: A common degenerative joint disease, often called "wear-and-tear arthritis."

  • Cause: Progressive loss of articular cartilage, leading to bone-on-bone friction.

  • Symptoms: Joint pain (especially with activity), stiffness, tenderness, loss of flexibility, grating sensation.

  • Location: Primarily affects weight-bearing joints (e.g., knees, hips, spine) and hands.

  • Prevalence: Common in older adults.

  • Onset: Gradual.

• Rheumatoid Arthritis (RA):

  • Description: An autoimmune disease.

  • Cause: Immune system attacks the synovial membranes, leading to chronic inflammation.

  • Symptoms: Joint pain, swelling, stiffness (especially in the morning), fatigue, often symmetric joint involvement.

  • Location: Commonly affects the hands, wrists, feet, and knees, often in a symmetrical pattern.

  • Treatment: DMARDs (disease-modifying antirheumatic drugs), biologics, NSAIDs, corticosteroids, physical therapy.

• Comparison: Gout (metabolic disorder), OA (degenerative, wear-and-tear), RA (autoimmune disease).

Joint Replacement Surgery

• Indications: Severe OA, RA, trauma.

• Goals: Replace damaged cartilage/bone with prosthetic components; restore alignment, stability, and mobility.

• Common procedures: Knee replacement, Hip replacement.