Canis ISSN: 2398-2942

Arthritis: osteoarthritis

Synonym(s): DJD, osteoarthritis, osteoarthrosis, secondary joint disease

Contributor(s): John Innes, Melvyn Pond

Introduction

  • Progressive disorder of movable joints characterized by degeneration of articular cartilage and production of new bone at articular margins - the end-stage of a variety of pathological processes.
  • The most frequently encountered joint disease - synonyms are osteoarthritis (emphasises the inflammatory nature of condition), osteoarthrosis (pathological process different from acute inflammatory process) and secondary joint disease (initiating factors have been identified, eg joint instability due to abnormal conformation, ligament rupture or intra-articular fractures).
  • Cause: often multifactorial.
  • Signs: insidious onset lameness of one or more limbs, pain on palpation/manipulation, thickened joints in advanced cases with crepitus.
  • Treatment: various - medical and surgical dependent upon stage and severity of condition.
  • Prognosis: surgery may remove signs but may not retain joint function.
  • In old animals, may be a major factor in the decision for euthanasia.
  • Osteoarthritis classification may be primary (idiopathic) or secondary (to an identifiable joint disease).

Pathogenesis

Etiology

  • Trauma: a single severe injury or low-grade repeated trauma, eg abnormalities of joint anatomy/structure, conformational abnormalities, instability due to severe joint trauma.
  • Repetitive joint concussion.
  • ?Genetic - primary OA.

Predisposing factors

General

Pathophysiology

  • Stress on normal or abnormal cartilage → enzymatic degradation of articular cartilage → softening of cartilage → progressive cartilage degradation → remodelling and osteophytosis.
  • Represents the end-stage of a variety of pathological processes: likely that both biochemical and biomechanical processes are involved → degeneration of articular cartilage and production of new bone at articular margins.

Biochemical theory

  • ?Cartilage wear particles → released into synovial fluid → irritant stimulation of resident joint cells → to produce mediators of connective tissue remodeling → biochemical cartilage degradation.
  • Intrinsic (arising from cartilage itself - chondrocytes more likely) or extrinsic (arising from synovial tissue) degradative enzymes (proteoglycanases (especially), neutral proteases) → proteoglycan degradation → massive decrease in molecular weight of proteoglycan-hyaluronate aggregates → increase in water from articular cartilage and loss of stiffness of collagen network → increased friction → increased probability of mechanical disruption of cartilage →cartilage erosion.
  • Blood vessel proliferation in region of cartilage erosion; or venous congestion; or stimulation of peripheral cells to undergo endochondral ossification by low grade synovitis at joint margins (joint movement seems to be involved - immobilization markedly reduces osteophyte formation) → new bone production: osteophyte formation→ subchondral bone remodeling.
  • Severe joint trauma → abnormalities of joint anatomy/conformation or joint instability → amplify wear and tear on joint surfaces → abnormal distribution of forces across joint surfaces.
  • Synovial membrane cells → activated by repeated trauma → stimulates release of interleukin → prostaglandin and neutral metalloproteinases by chondrocytes → pain and cartilage degradation.

Biomechanical theory

  • ?Repetitive concussion to joints → trabecular microfractures or direct stimulation to bone deposition → remodeling of subchondral bone → increased stiffness and reduced shock absorbing capacity → increased forces absorbed by articular cartilage → mechanical fragmentation of cartilage.
  • Biochemical and biomechanical theories of DJD are not mutually exclusive and it is likely that both act in concert in DJD.

Timecourse

  • Months to years.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Boileau C, Martel-Pelletier J, Caron J, Msika P, Guillou G B, Baudouin C & Pelletier J P (2009) Protective effects of total fraction of avocado/soybean unsaponifiables on the structural changes in experimental dog osteoarthritis: inhibition of nitric oxide synthase and matrix metalloproteinase-13. Arthritis Res Ther 11 (2), R41 PubMed.
  • Sanderson R O, Beata C, Flipo R-M, Genevois J-P, Macias C, Tacke S, Vezzoni A & Innes J F (2009) Systematic review of the management of canine osteoarthritis. Vet Rec 164, 418-424 PubMed.
  • Au R Y, al-Talib T K, Au A Y, Phan P V & Frondoza C G (2007) Avocado soybean unsaponifiables (ASU) suppress TNF-alpha, IL-1beta, COX-2, iNOS gene expression, and prostagalndin E2 and nitric oxide production in articular chondrocytes and monocyte/macrophages. Osteoarthritis Cartilage 15, 1249-1255 PubMed.
  • Chan P S, Caron J P, Rosa G J M & Orth M W (2005) Glucosamine and chondroitin sulfate regulate gene expression and synthesis of nitric oxide and porstaglandin E2 in articular cartilage explants. Osteoarthritis Cartilage 13 (5), 387-394 PubMed.
  • Neil K M, Caron J P & Orth M W (2005) The role of glucosamine and chondroitin sulfate in treatment for and prevention of osteoarthritis in animals. JAVMA 226 (7), 1079-1088 PubMed.
  • Innes J F, Fuller C J, Grover E R, Kelly A L & Burn J F (2003) Randomised, double-blind, placebo-controlled parallel group study of P54FP for the treatment of dogs with osteoarthritis. Vet Rec 152 (15), 457-460 PubMed.
  • Canapp S O, McLaughlin R M, Hoskinson J J, Roush J K & Butine M D (2000) Scintigraphic evaluation of glucosamine HC1 and chondroitin sulfate as treatment for acute synovitis in dogs. Am J Vet Res 60 (12), 1552-1557 PubMed.
  • Boon G K (1997) Synovial fluid analysis - a guide for general practitioners. Vet Med 92 (5), 443-451 AGRIS FAO.
  • Johnston S A & Fox S M (1997) Mechanisms of action of anti-inflammatory medications used for the treatment of osteoarthritis. JAVMA 210 (10), 1486-1492 PubMed.
  • Michels G M & Carr A P (1992) Non-infectious, non-erosive arthritis in dogs. Vet Med 92 (9), 798-803 VetMedResource.
  • Ellison R S (1988) The cytologic examination of synovial fluid. Semin Vet Surg 3 (2), 133-139 PubMed.

Other sources of information

  • Demko J L, Phan P V, Kramer E A, McLaughlin R & Frondoza C G (2007) Inhibition of prostaglandin E-2 production in chondrocyte microcarrier spinner cultures by the combination of avocado soy unsaponifiables, chondroitin sulfate and glucosamine. Proceedings of the 34th Annual Conference of the Veterinary Orthopedic Society, 25.


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