Page 167 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

142 CHAPTER 1

VetBooks.ir 1.256 FETLOCK JOINT OSTEOARTHRITIS

Definition/overview
Degenerative joint disease involving the metacarpo/
tarsophalangeal joint.

Aetiology/pathophysiology
Development of articular cartilage loss, subchondral
bone sclerosis, periarticular osteophyte and enthe-
seophyte formation, subchondral cystic formation
and eventually joint collapse can be seen in horses
of any age. It can be a sequela to, or associated with,
intra-articular insults such as sprain/luxation, villo-
nodular synovitis, intra-articular fracture, synovial
sepsis and OCD.

Clinical presentation
Horses often present with moderate lameness and a
Fig. 1.256 Lateromedial radiograph of a synovial effusion may be detected on physical exam-
metacarpophalangeal joint with chronic proliferative ination. Lameness is exacerbated by distal limb flex-
synovitis showing a crescent-shaped radiolucency ion and in chronic cases periarticular thickening and
on the dorsal aspect of the sagittal ridge due to pain may restrict range of motion.
cortical lysis. Note also the dorsal fetlock soft-tissue
enlargement with mild ossification, and signs of Differential diagnosis
osteoarthritis of the fetlock joint (remodelling of the Villonodular synovitis; fracture; sprain/joint trauma.
proximal aspect of the proximal sesamoid bone).
Diagnosis
Clinical examination may lead to a suspicion of
1.257
fetlock OA. Intra-articular or perineural analgesia
will usually assist in the localisation of lameness.
Radiographic signs of OA in the fetlock include
periarticular osteophyte formation (particularly
proximodorsal aspect of P1 and dorsoproximal and
dorsodistal margins of PSBs), modelling of proximal
aspects of the dorsal and palmar sagittal ridges, sub-
chondral bone sclerosis, irregular basilar fragments
and joint space reduction (Figs. 1.258, 1.259).
Nuclear scintigraphy may show increased radiophar-
maceutical uptake in the fetlock region with OA.

Management
Management in cases with mild changes includes
Fig. 1.257 Arthroscopic view of the dorsal pouch intra-articular medication (e.g. hyaluranon/cortico-
of the fetlock joint of a 2-year-old Thoroughbred steroids). Continued joint degeneration will result in
racehorse. Note the enlarged dorsal plica with progression of the disease and treatment is therefore
synovial proliferation and mineralisation (bright white often palliative. Injection of stem cells or other bio-
substance). (Photo courtesy Graham Munroe) logical agents (such as autologous conditioned serum)