Page 244 - Adams and Stashak's Lameness in Horses, 7th Edition

210 Chapter 3

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Figure 3.37. Caudocranial (CdCr) projection of the stifle. There
is a large, well‐defined ovoid radiolucent subchondral bone defect
(cyst) surrounded by a rim of sclerosis in the medial femoral
condyle (arrow). Subchondral cystic lesions of the medial femoral
Figure 3.35. Lateromedial (LM) projection of the stifle. Note the condyle can be a result of osteochondrosis or trauma.
well‐defined, oval, osseous body associated with a concave
subchondral bone defect on the lateral trochlea ridge (arrow),
consistent with osteochondritis dissecans. • Secondary osteoarthritic changes that may also be
present.
• Subchondral cyst‐like lesions that may develop
secondary to osteochondrosis.
• Joint distension may be present, particularly noticeable
in the tarsocrural joint.

traumatic JOint disease
Traumatic joint disease is caused by repetitive trauma
that causes microfracture and bone necrosis and can
lead to subchondral lysis, cystic lesions, and fragmenta­
28
tion. Areas of predilection for traumatic joint disease
are the metacarpophalangeal joints (Figure 3.38) and
carpus (Figure 3.39). Traumatic joint disease may also
develop after hyperextension injury in joints such as the
carpus, producing microfractures, subchondral bone lysis,
and small subchondral bone fragments. The following
are radiographic signs of traumatic joint disease:
• Focal subchondral bone lysis with indistinct borders
• Subchondral bone sclerosis
• Bone fragments, which may be adjacent to the sub­
chondral bone lysis
• Incomplete articular fractures or subchondral fissures
Figure 3.36. Mediolateral (ML) projection of the shoulder. A (stress fractures)
large radiolucent subchondral bone defect (cyst) surrounded by a • Changes in contour of the bones, such as flattening of
rim of sclerosis is seen on the caudal aspect of the humeral head the articular surface
(arrow), consistent with osteochondrosis.

• Flattening of the subchondral bone surface with adja­ LIMITATIONS OF RADIOGRAPHY
cent subchondral bone sclerosis.
• Localized subchondral bone defect, typically well Radiography is the most common imaging modality and
defined and generally smooth. is widely used for the diagnosis of musculoskeletal inju­
• Osteochondral bone fragments, which are seen radio­ ries. While an excellent screening tool, radiography has
graphically as osseous bodies representing osteochon­ well‐known limitations. Radiography allows identification
dritis dessecans. of soft tissue thickening and indirect evidence of soft