Page 163 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

138 CHAPTER 1

VetBooks.ir 1.248 1.249

Figs. 1.248, 1.249 Standing lateromedial radiographs of two fetlock joints with proximal dorsal sagittal
ridge osteochondrosis (OCD) lesions. The small OCD fragment is sat within a defect in the proximal ridge
(1.248) or visible more clearly as a rounded, apparently separate fragment (1.249).

OSTEOCHONDROSIS lameness and effusion whereas horses with OCD
involving the palmar aspect of the joint tend to be
Definition/overview lamer. Horses with OCLLs may present with inter-
OCD of the fetlock includes OCD of the sagittal mittent moderate-severe lameness, which is exacer-
ridge of the distal third metacarpus and OCLLs of bated by distal limb flexion.
the condyle of distal third metacarpus. Cystic lesions
can also be found in the PSB associated with septic
or non-septic osteitis. Osteochondral fragmentation 1.250
of P1 is dealt with separately.

Aetiology/pathophysiology
OCD can manifest itself in all four fetlock joints
and is seen as flattening of the sagittal ridge to dis-
secting lesions and fragmentation in young horses
(6–24 months old). Lesions are often present in the
dorsal aspect of the sagittal ridge (Figs. 1.248, 1.249)
but can also be seen in the palmar region (Fig. 1.250).
OCLLs usually involve the condyle of the distal
third metacarpus (Figs. 1.251, 1.252) and present
in young horses (1–2 years old). Rarely, OCLLs may
involve proximal P1 near the sagittal groove and may
be associated with short, incomplete P1 fractures.

Clinical presentation
Young horses usually present with variable lameness Fig. 1.250 Standing lateromedial radiograph of a
and/or fetlock joint effusion(s). Horses with OCD palmar fetlock osteochondrosis fragment just dorsal to
involving the dorsal sagittal ridge present with mild the proximal sesamoid bone.