Musculoskeletal System
April 2019

Signalment (JPC #161962):  A 7-year-old male guinea pig

HISTORY:  This guinea pig had a 6-month history of progressive debilitation and inability to use the hind legs.

HISTOPATHOLOGIC DESCRIPTION:  Stifle joint, bone and articular cartilage:  Diffusely, the articular cartilage is either completely lost (ulcerated) or is thin with decreased matrix basophilia (loss of proteoglycans), multifocal fraying (fibrillation) of the surface cartilage, multifocal clefts perpendicular to the joint space that extend into the deep cartilage layers, and occasional clusters of disorganized hyperplastic chondrocytes (chondrones).  In areas of cartilage ulceration, the exposed bone is thickened up to 10x normal (sclerosis, eburnation).  Subchondral bone multifocally contains multiple cysts, up to 0.5mm in diameter, lined by a single layer of flattened to cuboidal cells.  These cysts occasionally contain eosinophilic fibrillar material and are surrounded by loosely-arranged spindle cells, mild hemorrhage, and hemosiderin-laden macrophages.  Multifocally at the joint margins, there are multiple cartilage-capped, irregularly-shaped proliferations of trabecular woven and lamellar bone (osteophytes) with numerous basophilic resting and reversal lines, and proliferations of fibrocartilage.  The proliferations of bone multifocally have a scalloped irregular margin with few osteoclasts present (remodeling).  The joint capsule is markedly expanded by mature fibrous connective tissue, and the synovial membrane is mildly thickened multifocally, occasionally forming papillary projections composed of hypertrophied and hyperplastic synoviocytes supported by well-vascularized connective tissue.  Within the joint space, there are low numbers of lymphocytes and necrotic mononuclear cells (synoviocytes or macrophages) mixed with eosinophilic granular to amorphous material.

MORPHOLOGIC DIAGNOSIS:  Stifle joint, bone and articular cartilage:  Cartilage degeneration, erosion, and ulceration, diffuse, severe, with fibrillation, clefting, periarticular osteophytes, subchondral bone sclerosis, and subchondral bone cysts (degenerative joint disease), guinea pig (Cavia porcellus), rodent.

CONDITION:  Degenerative joint disease (DJD)

SYNONYMS:  Osteoarthritis, osteoarthrosis, degenerative arthropathy










  1. Barthold SW, Griffey SM, Percy DH. Pathology of Laboratory Rodents and Rabbits. 4th ed. Ames, IA: Blackwell Publishing; 2016: 105, 159, 246.
  2. Bolon B, Grisanti M, Villasenor K, Morony S, Feige U, Simonet WS. Generalized degenerative joint disease in osteoprotegerin (Opg) null mutant mice. Vet Pathol. 2015;52(5):873-882.
  3. Craig LE, Dittmer KE, Thompson KG. Bones and joints. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 3. 6th ed. St. Louis: Elsevier; 2016:137-146.
  4. Engiles JB, Stewart H, Janes J, Kennedy LA. A diagnostic pathologist’s guide to carpal disease in racehorses.  Jour Vet Diagn Invest. 2017;29(4):414-430.
  5. Harkema L, Youssef SA, de Bruin A. Pathology of mouse models of accelerated aging.  Vet Pathol. 2016;53(2):366-389.
  6. Hufschmid J, Beveridge I, Coulson G, et al. Skeletal pathology of Eastern grey kangaroos (Macropus giganteus) exposed to high environmental fluoride levels in South-Eastern Australia. J Comp Pathol. 2015;153(2-3):167-184.
  7. Lin AW, Vapniarsky N, Cissell DD, et. al. The temporomandibular joint of the domestic dog (Canis lupus familiaris) in health and disease.  Jour Comp Pathol. 2018;161:55-67.
  8. McCoy AM. Animal models of osteoarthritis: comparisons and key considerations. Vet Pathol. 2015;52(5):803-818.
  9. Olson EJ, Carlson CS. Bones, joints, tendons and ligaments. In:  McGavin MD, Zachary JF, eds. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Elsevier; 2017: 1001-1004.
  10. Pritzker KPH, Kessler MJ. Arthritis, muscle, adipose tissue, and bone diseases of nonhuman primates. In: Abee CR, Mansfield K, Tardif S, Morris T, Morris T, eds.  Nonhuman Primates in Biomedical Research.  London, UK: Academic Press; 2012: 631-639.
  11. Schauer AM, Schucker A, Carlson CS. Dystrophic mineralization of costal cartilage in Hartley guinea pigs.  Toxiocol Pathol.  2017;45(3):435-439.
  12. Simmons HA. Age-associated pathology in rhesus macaques (Macaca mulatta). Vet Pathol. 2016;53(2):399-416.

Click the slide to view.

Click on image for diagnostic series.

Back | Home | Contact Us | Links | Help |