Felis ISSN 2398-2950

Arthritis: osteoarthritis

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

Contributor(s): Eithne Comerford, David Godfrey, 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: emphasizes the inflammatory nature of condition.
    • Degenerative joint disease (DJD): deliberately broad term that encompasses osteoarthritis along with other predominantly degenerative conditions.
    • Osteoarthrosis: pathological process different from acute inflammatory process.
    • Secondary joint disease: initiating factors have been identified, eg joint instability due to abnormal conformation, ligament rupture or intra-articular fractures.
  • Osteoarthritis classification may be primary (idiopathic) or secondary (to an identifiable joint disease).
  • Cause: in cats this is not well established but it appears to be idiopathic in the considerable majority of cases. In other species it is often multifactorial: congenital/developmental abnormalities, obesity, trauma and other acquired disease are significant factors.
  • Signs: insidious onset change in normal behavior with a reduction in activity levels is the commonest sign observed by owners, lameness of one or more limbs, pain on palpation/manipulation, change of temperament, and poor grooming.
  • Treatment: environmental modification and medical treaments are usual. Surgical treatment would be rare. No treatment is required for pure radiographic signs if no clinical signs are evident but a short trial treatment with an analgesic may be appropriate to ensure that clinical signs have not gone unobserved.
  • Prognosis: this is a slowly progressive condition that often goes unnoticed by owners. Medical and/or surgical treatment may alleviate pain, decrease inflammation, improve function and slow progress of degenerative joint disease (DJD).
  • One of the commonest clinical problems of cats. Much overlooked and underdiagnosed in the past. The commonest musculoskeletal condition in cats.
Use the interactive tool from ROYAL CANIN® UK  to explain cat anatomy and disease conditions to your client. Visit ROYAL CANIN Natom Explorer to find out more.

Pathogenesis

Etiology

  • Unproven in cats although at least 80% of cases seem to be idiopathic.
  • Trauma: a single severe injury or low-grade repeated trauma, eg abnormalities of joint anatomy/structure, conformational abnormalities, instability due to severe joint trauma, contra-lateral amputation.
  • Repetitive joint concussion if unproven to be important in cats.
  • ?Genetic - primary OA - has not been shown to occur in cats.
  • Obesity Obesity is suspected to be a significant factor but this has not yet been proven in cats.

Predisposing factors

General

  • Joint instability as a result of ligamentous damage,  eg carpal collapse syndrome with diabetes mellitus, or cranial cruciate ligament damage are potential causes.
  • Joints most commonly affected are the elbow and hip. The shoulder, stifle and tarsus seem to be more commonly affected than the carpus or the digital joints.

Pathophysiology

These theories are extrapolated from other species.

  • Stress on normal or abnormal cartilage    →   enzymatic degradation of articular cartilage    →   softening of cartilage    →   progressive cartilage degradation    →   remodeling 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 (aggrecanases (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 OA are not mutually exclusive and it is likely that both act in concert in OA.

Timecourse

  • Months to years. Although, radiographically and histopathologically, features of DJD can be seen within days of experimentally-induced joint instability.

Diagnosis

This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login

Treatment

This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login

Prevention

This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login

Outcomes

This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Au R Y, al-Tabib T K, Au A Y et al (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 (11), 1249-1255 PubMed.
  • Clarke S P & Bennett D (2006) Feline osteoarthritis: a prospective study of 28 cases. JSAP 47 (8), 439-445 PubMed.
  • Clarke S P, Mellor D, Clements D N et al (2005) Prevalence of radiographic signs of degenerative joint disease in ahospital population of cats. Vet Rec 157 (25), 793-799 PubMed.
  • Godfrey D R (2005) Osteoarthritis in cats: a retrospective radiological study. JSAP 46 (9), 425-429 PubMed.
  • Leonard C A & Tillson M (2001) Feline Lameness. Vet Clin North Am Small Anim Pract 31 (1), 143-163 PubMed.
  • Bardet J F (1998) Diagnosis of shoulder instability in dogs and cats - a retrospective study. JAAHA 34 (1), 42-54 PubMed.
  • Hulse D (1998) Treatment methods for pain in the osteoarthritis patient. Vet Clin North Am Small Anim Pract 28 (2), 361-375 PubMed.
  • Langenbach A, Green P, Giger U et al (1998) Relationship between degenerative joint disease and hip joint laxity by use of distraction index and Norberg angle measurement in a group of cats. JAVMA 213 (10), 1439-1443 VetMedResource.
  • Boon G K (1997) Synovial fluid analysis - a guide for small-animal practitioners. Vet Med 92 (5), 443-451 AGRIS FAO.
  • Hardie E M (1997) Management of osteoarthritis in catsVet Clin North Am Small Anim Pract 27 (4), 945-953 PubMed.
  • Harari J (1997) Clinical evaluation of the osteoarthritic patient. Vet Clin North Am Small Anim Pract 27 (4), 725-734 PubMed.
  • Hoskins J D, Kerwin S C (1997) Musculoskeletal system. Joint and vertebral column diseases. Vet Clin North Am Small Anim Pract 27 (6), 1433-1449 PubMed.
  • Johnston S A (1997) Osteoarthritis - joint anatomy, physiology and pathobiology. Vet Clin North Am Small Anim Pract 27 (4), 699-723 PubMed.
  • 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.
  • Ellison R S (1988) The cytologic examination of synovial fluid. Semin Vet Med Surg (Small Anim) (2), 133-139 PubMed.

Other sources of information

  • Punke J P, Au R Y, Au A Y, Phan  P, Budsberg S C & Frondoza C G (2007) Modulation of protstaglandin E-2 production in feline articular chondrocytes propagated in monolayer and dynamic microcarrier culture. American College of Veterinary Surgeons Symposium, poster.


ADDED