Page 243 - Adams and Stashak's Lameness in Horses, 7th Edition

Diagnostic Imaging 209

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Figure 3.32. Caudocranial (Ca‐Cr) projection of the stifle. A
rounded periarticular osteophyte is present on the medial
periarticular margin of the medial tibial condyle, consistent with Figure 3.33. Dorsomedial to palmarolateral oblique (DMPLO)
osteoarthritis (white arrow). The articular surface of the medial projection of the metacarpophalangeal joint. An area of permeative
femoral condyle has a slight concave defect (short black arrow). lysis is present on the dorsal aspect of the lateral condyle of MCIII.
The horizontal radiopaque line on the cranial margin of the medial Marked narrowing of the joint space, mild irregular periosteal
femoral condyle (long black arrows) indicates enthesophytosis at the reaction on the dorsolateral aspect of proximal P1, and associated
insertion of the medial femorotibial and medial aspect of the soft tissue thickening with subcutaneous gas are also present.
femoropatellar joint capsules. These findings are consistent with septic arthritis.

septic arthritis
In foals, septic arthritis is most commonly hematog­
enous in origin. Septic arthritis in adult horses typically
occurs from penetrating wounds, as an iatrogenic conse­
quence of needle centesis or, less frequently, an extension
of adjacent osteomyelitis or cellulitis. (Figures 3.29 and
3.33). The following are radiographic signs of septic
arthritis:
• Periarticular soft tissue thickening and joint distension.
• Marginal bone lysis, which may occur early in the
disease.
• Subchondral bone destruction, which may be an
extension from or occur without the marginal lysis.
• Periosteal reactions, which may be adjacent to the
joint but are generally distributed around the joint;
when septic arthritis has occurred from extension of
an adjacent osteomyelitis or cellulitis, the periosteal
reaction may precede the intra‐articular changes.

OsteOchOndrOsis
Osteochondrosis is associated with regions of high
predilection in specific joints, which should be observed
when diagnosing the condition. In the horse, the stifle,
tarsus, and fetlock are most commonly affected by oste­
ochondrosis, although lesions can be found in all joints. Figure 3.34. Dorsolateral to palmaromedial (DLPMO) projection
It is caused by defective osteochondral development, of the tarsus. There is a well‐defined, irregular lucent line through
which usually involves subchondral bone (Figures 3.34– the distal intermediate ridge of the tibia with an associated osseous
3.37). The following are radiographic changes present fragment (arrow). There is mild sclerosis surrounding the lesion.
with osteochondrosis: This is a common site of osteochondritis dissecans (OCDs).