Rheumatoid factor is present in the serum of 85–90% of patients with
rheumatoid arthritis. Deposition of rheumatoid factor can be pathogenic and
leads to inflammatory destruction of the joint surface. Cell-mediated immu-
nity is also involved in rheumatoid arthritis. Alteration of the synovial mem-
brane results in the formation of a pannus, or inflammatory, hypertrophic
synovial villus. The presence of the pannus and release of lysosomal enzymes
from the pannus result in degradation of the cartilage. This is followed by
hypertrophy and hyperplasia of the articular cartilages, which often leads to
bone formation across the joint with welding of the bones together (ankylosis).
Because of the inflammation in rheumatoid arthritis, there are elevated num-
bers of leukocytes (answer d),in particular PMNs, in the synovial fluid. Dur-
ing rheumatoid arthritis, fibrinogen (answer b), another indicator of
inflammatory responses, is elevated. Osteoarthritis begins with loss of
hydrated glycosaminoglycans, followed by death of chondrocytes, fibrilla-
tion, and development of fissures in the articular cartilage matrix (answer a).
The severe wear and tear of osteoarthritis increases with age. During the
breakdown of the articular cartilages, the width of the underlying bone
increases. Osteoarthritis typically includes the formation of reactive bone
spurs called osteophytes (answer c),which may break off to form foreign
bodies in the joint space (i.e., “joint mice”). In the fingers, osteoarthritis pri-
marily affects distal interphalangeal joints, where it produces painful nodular
enlargements called Heberden’s nodes. Large weight-bearing joints are also
usually involved in osteoarthritis and often exhibit eburnation in the late
stages, when the articular cartilages have been worn down, and result in an
osseous articular surface.
110.The answer is c.(Junqueira, pp 145, 147. Kumar, pp 1288–1289.)
The most common type of wrist fracture is a Colles’ fracture. The location
of the break is between 2 and 3 cm from the wrist joint at the point where
the radius narrows from cancellous bone forming the joint to the cortical
bone of the shaft of the radius. In the healing of fractures, the first step is
clotting of extravasated blood. The clot is organized into a callus by granu-
lation tissue (answer e)that consists of fibroblasts, osteogenic cells, and
budding capillaries. An internal, bony callus (answer a)forms where local
bone factors are most active (i.e., in close proximity to the periosteum and
endosteum that retain osteogenic potential). An external, cartilaginous
(answer b)callus forms bone by endochondral ossification following ini-
tial chondrogenesis. These steps involve repetition of the cellular events
Specialized Connective Tissues: Bone and Cartilage Answers 209