Joint medications

RELEVANT READING MATERIAL

  • Chapter Reference: Chapter 80, Pages 1348 - 1363, Auer & Stick Equine Surgery, Fifth Edition, Elsevier

    • Authors: Auer, Stick, Kümmerle & Prange

    • Focus Area: Equine Surgery

CARTILAGE BEHAVIOR

  • Quote: "Cartilage once destroyed never heals" - Hunter W, 1743

    • Implication: The irreparability of cartilage injury underscores the importance of preventive measures in joint health.

JOINT ANATOMY

  • Components of a Healthy Joint:

    • Synovial Membrane: Critical for joint lubrication and nutrient supply.

    • Joint Capsule: Encloses the joint and contains synovial fluid.

    • Cartilage: Protective covering on the articulating surfaces of bones.

    • Subchondral Bone: Bone layer beneath the cartilage, providing structural support.

    • Articular Cartilage: Serves as the joint surface; composed primarily of water (80%), proteoglycans (PG), hyaluronic acid (HA), and collagen.

    • Synovial Fluid: Provides lubrication and reduces friction within the joint.

    • Synoviocytes: Cells within the synovial membrane that play roles in joint maintenance.

    • Vasculature: Blood supply to the joint structures.

SYNOVIAL MEMBRANE

  • Structure:

    • Two Layers:

    • Subintimal Layer: Provides blood supply and innervation.

    • Intimal Layer: Contains synoviocytes, predominantly:

      • Macrophage Type A: Engaged in phagocytosis (removal of debris).

      • Fibroblast Type B: Produces extracellular matrix components.

  • Components:

    • Hyaluronic Acid: Maintains viscosity of synovial fluid, providing joint lubrication.

    • Aggrecan: A major proteoglycan found in cartilage that helps maintain its structure.

    • Cytokines: Important for mediating inflammation and joint health.

    • Eicosanoids & Proteases: Involved in inflammatory responses.

SUBCHONDRAL BONE

  • Function:

    • Acts as a “shock absorber” during joint movements, handling forces and loads.

    • More deformable than cortical bone, allowing for dynamic movement.

    • Sclerosis: Increased bone density may indicate conditions such as osteoarthritis (OA).

ARTICULAR CARTILAGE

  • Characteristics:

    • Key factor in defining joint health; irregularities indicate disease.

    • Structure includes specialized extracellular matrix essential for load distribution.

  • Composition:

    • Water: Makes up 80% of cartilage.

    • Proteoglycans (PG), Hyaluronic Acid (HA), and various types of collagen.

PROTEOGLYCANS

  • Definition: Consist of protein core with glycosaminoglycan (GAG) chains.

  • Roles:

    • Aggrecan forms aggregates with HA, significantly contributing to cartilage resilience and shock absorption.

OVERALL JOINT HEALTH

  • Factors impacting joint health:

    • Degradation: Includes breakdown of cartilage in OA.

    • Synthesis: Involves the production of components that preserve joint structures, influenced by various cytokines and growth factors:

    • Anti-inflammatory Cytokines: Such as IL-4, IL-10, IL-13.

    • Proinflammatory Cytokines: Include IL-1β, TNF-α, IL-6, IL-8, IL-11, IL-17, IL-18, which contribute to cartilage degradation.

    • Matrix Metalloproteinases (MMPs): Enzymes responsible for ECM breakdown (collagenases, stromelysin, gelatinases).

    • Aggrecanases: Specifically target aggrecan leading to cartilage loss.

    • Nitric Oxide: Involved in inflammatory processes.

    • Growth Factors: e.g., IGF-I, TGF, bFGF, BMPs - support collagen and PG synthesis.

    • Timps (Tissue Inhibitors of Metalloproteinases): Regulate MMP activity, promoting cartilage health.

CARTILAGE IN OSTEORTHRITIS

  • Clinical Parameters:

    • Effusion: Increased fluid in the joint space; can indicate joint pathology.

    • Decreased Viscosity of Synovial Fluid: Impairs joint lubrication and health.

    • Increased Total Protein (TP): Reflects changes in synovial fluid indicative of pathologies.

    • Gross Cartilage Changes: Characterized by altered appearance (yellow, fibrillated, dull, ulcerated, pitted).

SUBCHONDRAL BONE IN JOINT DISEASE

  • Pathological Alterations:

    • Sclerosis: Increased density and strength may complicate joint function.

    • Osteophyte Formation: Bone growth along the edges of joints.

    • Enthesiophyte Formation: New bone growth at tendon or ligament attachment sites.

SYNOVIAL MEMBRANE/JOINT CAPSULE IN JOINT DISEASE

  • Response to Disease:

    • Pain and decreased range of motion are common symptoms.

    • Chronic inflammation results in thickening of the membrane (hypertrophy) and fibrosis (scarring) in synovial tissue.

CLINICAL SIGNS OF OSTEOARTHRITIS

  • Common Symptoms:

    • Lameness

    • Joint Pain

    • Decreased Range of Motion

    • Joint Effusion: Indicates inflammation or other disorders.

ACTIVATORS IN JOINT DISEASE

  • Cell Types Involved:

    • Synoviocytes: Stimulate inflammation and joint degradation.

    • Fibroblasts: Contribute to extracellular matrix remodeling.

    • Neutrophils: Involved in the inflammatory response.

    • Chondrocytes: Key cells in cartilage maintenance and degradation processes.

  • Cytokines:

    • IL-1 and TNF-α: Major proinflammatory cytokines driving degeneration.

  • Matrix Degradation: Mediated by metalloproteinases and serine proteinases.

TREATMENT GOALS

  • Clinical Objectives:

    • Reduce/minimize inflammation

    • Slow progression of degeneration

    • Reduce/eliminate pain

    • Restore normal synovial fluid characteristics

TREATMENT OPTIONS

  • Medications:

    • Chondroprotectives: e.g., HA, PSGAGs, PG.

    • Corticosteroids: Anti-inflammatory action, but risk of cartilage damage if misused.

    • NSAIDs: Non-steroidal anti-inflammatory drugs help manage pain and inflammation.

    • Blood-based Products: Therapies derived from autologous blood.

    • Cell-based Treatments: Innovative therapies utilizing stem cells and progenitor cells.

CHONDROPROTECTIVE AGENTS

  • Hyaluronic Acid (HA):

    • Definition: A long-chain, unbranched non-sulfated GAG, integral for joint health.

    • Functions include:

    • Enhancing viscoelastic properties of synovial fluid.

    • Providing boundary lubrication within joints.

    • Modulating chemotactic responses and scavenging free radicals.

    • Supporting the production of endogenous HA and decreasing degradation of aggrecan.

HYALURONIC ACID RESEARCH

  • Efficacy Studies:

    • Frisbie et al. (2009): Evaluated HA's analgesic properties.

    • Richardson & Loinaz (2007): Discussed HA's effects on cartilage degeneration.

  • Dosage Recommendations:

    • For lameness improvement: 20mg per joint, typically once weekly for 3 weeks.

    • In humans, at least 3 doses, one week apart, showed significant improvements in pain and effusion.

HYALURONIC ACID ADMINISTRATION

  • Intravenous (IV) vs. Intra-Articular (IA):

    • IA: More targeted and effective for specific joint issues.

    • IV: Less effective for isolated joints but helpful for multiple joint conditions.

COMBINATION THERAPIES

  • HA with Triamcinolone:

    • Combining HA's chondroprotective effects with the anti-inflammatory action of Triamcinolone may provide synergistic benefits.

POLYSULFATED GLYCOSAMINOGLYCANS (PSGAGs)

  • Mechanism of Action:

    • Inhibits degrading enzymes and counters IL-1 effects.

    • Facilitates improved glycosaminoglycan and collagen synthesis.

    • Enhances synovial membrane health.

  • Brand Name: Adequan, shown effective in recovery.

ADEQUAN DRAWBACKS

  • Risks:

    • Potential for increased infection with sub-infective doses of bacteria.

    • Antimicrobial treatments suggested alongside IA injections of Adequan.

POST-SURGICAL LAVAGE

  • Solutions Used:

    • Common formulations include:

    • Hyaluronic Acid (5mg/ml)

    • Chondroitin Sulfate (100mg/ml)

    • N-Acetyl-D-Glucosamine (100mg/ml)

POLYGLYCAN USAGE

  • Administration Requirements:

    • Must be given IA, as IV administration may worsen disease progression according to studies.

  • Recommendations: Carefully consider timing and method of administration based on individual case requirements.

CHOOSING BETWEEN HA AND PSGAGs

  • Comparative Efficacy:

    • Both have disease-modifying osteoarthritis drug actions.

    • HA shows superior effects on articular cartilage fibrillation, while PSGAGs on synovial membrane healing.

  • Clinical Decisions: Based on evidence and specific case scenario; HA may be more appropriate for mild synovitis.

CORTICOSTEROIDS

  • Types and Effects:

    • Triamcinolone Acetonide: Chondroprotective effects.

    • Methylprednisolone Acetate: Typically detrimental to cartilage at therapeutic levels.

    • Betamethasone: Neutral effects on cartilage.

LAMINITIS & CORTICOSTEROIDS

  • Clinical Observations:

    • No incidents of laminitis in 1200 horses with doses <18mg (Genovese 1983).

    • No association found in studies between laminitis and IA injections of Triamcinolone.

    • Review findings showed insufficient evidence linking corticosteroid use to laminitis; the occurrence was rare (0.15% of cases).

PROLONGED EFFICACY OF CORTICOSTEROIDS

  • Effects on Cartilage:

    • Prolonged receptor interactions result in continued benefits (up to 70 days).

    • The need for rest after administration is debated but evidence does not consistently show exercise as harmful.

BIOLOGICS IN JOINT DISEASE

  • Types of Biological Therapies:

    • IRAP/IRAP II: Interleukin-1 receptor antagonist proteins to lessen inflammation.

    • Platelet Rich Plasma (PRP): Concentrate of platelets promoting healing.

    • Pro-Stride: A variation of PRP with additional therapeutic properties.

    • Stem Cell Therapies: Utilizing allogeneic stem cells for cartilage regeneration.

POLYACRYLAMIDE HYDROGELS (PAAG)

  • Characteristics:

    • Synthesized hydrogel remains in synovial structures for long periods for therapeutic effects.

    • Common products include:

    • 4% Noltrex® Vet

    • 2.5% Arthramid® Vet

RECOMMENDED GUIDES FOR EQUINE PRACTICE

  • Essential Reference:

    • "A Guide to Equine Joint Injection and Regional Anaesthesia" (Second Edition) edited by William Moyer, John Schumacher, and Jim Schumacher (2011).

  • Importance of Comfort with Arthrocentesis: Essential for effective Intra-Articular (IA) use of joint medications.