Cartilage & Lower Extremity Joint Pain

Question 1

What are the 5 different kinds of cartilage?

Answer 1

Types of Cartilage

1. Physeal: growth plates
2. Fibrocartilage: at tendon & ligament insertions into bone
3. Elastic: found in trachea
4. Fibroelastic: found in meniscus
5. Articular/Hylan: covers ends of bones forming joints

Question 2

Describe the factors that play a role in the health of articular cartilage.

Answer 2

Articular cartilage depends on both biologic and mechanical factors to stay healthy:

Biologic Factors

• Collagen
• Synovial fluid
• Subchondral bone (for attachment) - this is required, without bone hylan cartilage becomes fibrocartilage

Mechanical Factors (depends on the joint’s ability to withstand the forces applied to it)

• Deformity
• Instability
• Abnormal forces
• Muscle weakness (ex. Trendelenburg’s sign/gait)
• Poor proprioception
• Mal-alignment
• Obesity

Healthy attachment to subchondral bone

Healthy synovial fluid with the right balance of

• Hyaluronic acid
• Libricin
• Proteinase
• Collagenase
• Prostaglandins

Question 3

What is the biological recipe for healthy articular cartilage?

Answer 3

Healthy Articular Cartilage Biology

• Water 65-80% wet weight
• Collagen (Type II): 20%
  
  • Provides tensile strength
  • Very stable - half-life is 25 years
• Proteoglycans: 10-15%
  
  • Provides elastic & compressive strength
  • Porous structure traps & holds water
  • Short half life (3 months)
• Condrocytes: 5%

Question 4

What ingredients are required to be in balance for healthy synovial fluid?

Answer 4

Healthy Articular Cartilage: Biology

• Depends on it’s attachment to healthy subchondral bone
• Depends on healthy synovial fluid with the right balance of
  
  • Hyaluronic acid
  • Lubricin
  • Proteinase
  • Collagenase
  • Prostaglandins

Question 5

What are some of the causes of abnormal forces on articular cartilage?

Answer 5

Healthy Articular Cartilage: Mechanical

• Depends on the joint’s ability to withstand the forces applied to the joint
• Abnormal forces can be the result of:
  
  • Instability
  • Muscle weakness ex. Trendelenberg sign/gait
  • Poor proprioception
  • Mal-alignment ex. varus/valgus
  • Obesity

Question 6

Explain what is happening in degenerative joint disease (osteoarthritis).

Answer 6

Degenerative Joint Disease (DJD)

• DJD is not the same as normal aging
• Failed attempt of the chondrocytes to repair damaged cartilage
• Damaged articular cartilage usually heals with fibrocartilage (not Hylan)
• Increased water content
• Decreased number of chondrocytes
• Decreased proteoglycan content
• Disrupted collagen

Question 7

What are the two different categories for the manifestation of arthritis?

Answer 7

Arthritis

Primary

• Degenerative
• Auto-immune

Secondary

• Vascular, Infectious/Inflammatory, Traumatic, Metabolic, Iatrogenic, Neoplastic, Congenital
• VITAMIN C&D

Question 8

What are the radiographic changes of arthritis?

Answer 8

Radiographic Featues of Arthritis

• Joint space narrowing
• Subchondral sclerosis
• Subchondral cysts
• Osteophytes (bone spurs)

Question 9

What is the role of obesity in arthritis of weight bearing joints? Describe a weight loss strategy.

Answer 9

Obesity results in more force per unit area on each joint. Therefore, joints are experiencing abnormal loading. More specifically, the force on articular cartilage exceeds the amount of force it is able to withstand without impeding cartilage health.

Weight loss requires the decision to make a lifestyle change. The patient must commit to a exercise and nutrition plan that is realistic and that meets their goals for weight loss. Pre-operation consultation is a good opportunity to discuss weight loss with patients as they will be motivated to increase the chances of a good outcome from surgery. Social support and encouragement are also important components of a weight loss plan.

Question 10

What are the goals of non-surgical management for OA?

Answer 10

• Optimize the joint environment
• Minimize abnormal forces on the joint

Question 11

What 3 surgical options are available for OA?

Answer 11

Surgical Management

• Realign = osteotomy
• Replace = joint replacement
• Obliterate = fusion or excision

Question 12

Differentiate between osteoarthritis and osteonecrosis.

Answer 12

Osteoarthritis: inflammation of joints

• Results from multiple factors: (1) joint integrity, (2) genetic presdisposition, (3) local inflammation (4) mechanical forces, and (5) cellular and biochemical processes

Osteonecrosis: decreased blood supply to bone causing death of the bone and marrow cells; this leads to mechanical failure of the joint

Question 13

What are the potential etiologies and risk fractors of avascular or osteonecrosis?

Answer 13

Etiology and Risk Factors of Avascular or Osteonecrosis:

• Vascular: sickle cell disease
• Infection/Inflammatory: viral and bacterial; SLE
• Trauma: fracture, dislocation
• Autoimmune: n/a
• Metabolic: EtOH, Gaucher’s Hyperlipidemia
• Iatrogenic/Idiopathic: Steroids
• Neoplastic: Multiple Myeloma, Irradiation-Induced