Page 848 - Adams and Stashak's Lameness in Horses, 7th Edition

814 Chapter 7

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A B C

D E
Figure 7.11. Diagrammatic series of development of osteoarthri- superficial fibrillation in the articular cartilage. (D) Stage 3 synovitis
tis in a fetlock joint associated with cyclic trauma and traumatic and capsulitis becoming chronic and articular cartilage fibrillation
synovitis and capsulitis. (A) Diagram of a normal joint, as well as down into the deep zone of articular cartilage. (E) Stage 4 develop-
macroscopic and microscopic views of articular cartilage. (B) Stage 1 ment of full‐thickness erosions in the articular cartilage that are visible
acute synovitis without morphologic change in the articular cartilage. macroscopically and microscopically. Joint capsule change is chronic
(C) Stage 2 with synovitis persisting and early development of with fibrosis, but some degree of active synovitis is still present.

radial direction and this structure, having lost its three‐ through the deeper layer of cartilage, which then allows
dimensional character, would have limited ability to con­ for loss of articular cartilage components and full‐thick­
tain the swelling proteoglycan aggregates remaining in ness erosion. Figure 7.11 illustrates four stages of OA in
the tissue and would therefore reflect a state of softening which the synovitis and capsulitis become more chronic.
in articular cartilage. 7 Close examination of articular cartilage shows change,
The most common reason for degradation of articu­ and the histologic equivalent of these macroscopic
lar cartilage and the development of OA is generally lesions is reflected as well.
synovitis and capsulitis. There is a progression, begin­
ning with acute synovitis, when biochemical change can Articular Cartilage Repair
take place in the articular cartilage, but there is no mor­
phologic change. With critical loss of matrical compo­ Healing refers to restoration of the structural integ­
nents, however, morphologic damage ensues, going rity and function of the tissue after injury or disease, but
through a cycle of chondromalacia with softening of the repair usually has a more restricted meaning. Repair
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cartilage and swelling due to absorption of water, super­ refers to the replacement of damaged or lost cells and
ficial fibrillation, and fibrillation down to the middle matrix with new cells and matrix, a process that does
zone of cartilage, followed by fibrillation progressing not necessarily restore the original structure or function