374 SHUPE
involvement resulting in secondary capsulitis, which later develops into the
progressive, degenerative joint lesions characteristic of osteoarthritis.
Stress and strain on joints, causing constant irritation, appear to be the most
important causes of degenerative arthritis or arthrosis. However, not all cases
can be attibuted to this cause. A relatively high incidence of this disease process
in certain family lines of cattle suggests the role of heredity, but no pattern of
inheritance has been established as yet.
The development of degenerative arthrosis to the stage of marginal osteophytic
formations requires from two to five years and follows a definite pattern. The first
discernible gross lesions occur in the articular cartilage. Following degeneration of
articular cartilage, subchondral bone changes take place. Subchondral cysts that
contain clear, yellowish fluid appear to be associated with early articular cartilage
degeneration. Adaptive processes advance as the disease progresses. Marginal
osteophytic formations cause malalignment and malocclusion of joints, with a
resultant increase in lameness. In advanced cases practically all joints in the
fore and hind limbs develop some degree of degenerative and hypertrophic
changes; however, the large, freely movable hip and stifle joints show the most
striking and severe lesions. This disease can occur in both the fore and the hind
limbs and may be uni- or bilateral. Progressive articular and bone changes result
in increasing lameness unaccompanied by systemic manifestations in most cases.
To understand joint diseases, one must bear in mind the anatomic and
histologic make-up of joints, and the four previously mentioned characteristics of
cartilage: (1) avascularity, (2) insensitivity, (3) low metabolic rate, and (4)
poor reparative ability. It is important to be familiar with the normal individual
variations and physiological processes of aging. The clinical manifestations may
vary from case to case and will be influenced by many factors such as the
biological response of the individual animal to the disease process.
SUMMARY
1. Joint lesions in the bovine species have been recognized since the beginning
of veterinary medicine.
2. Joint diseases in cattle are no single disease entity, but encompass a number
of different processes, the etiology and pathogenesis of which are known in only
some of the cases. Some of the processes are referred to as inflammatory, others
as degenerative joint diseases.
3. Some of the changes observed in degenerative joint disease are secondary
and result from the disuse of the malfunctioning joint or joints.
4. In general, inflammatory arthritis in cattle is accompanied by systemic
manifestations such as elevated body temperature, hot swollen joints, anorexia,
depressed appetite, suppressed ruminations, and obvious pain that is not
alleviated when the animal is recumbent.
5. Degenerative joint disease is seldom fatal, but often is a chronic debilitating
condition. It occurs in older animals and is most often observed in the larger,
freely movable joints. It is characterized by degeneration and hypertrophy of
cartilage and bone.
6. Pathologically inflammatory arthritis is proliferative in nature in its later