Page 707 - Adams and Stashak's Lameness in Horses, 7th Edition

Lameness of the Proximal Limb 673

Horses presenting with TC effusion should have a weight‐bearing parts of the trochlea of the talus can
complete lameness evaluation and should have radio- exist but may not be apparent on radiographic examina-
VetBooks.ir this joint. Horses may have a “bog” that persists for the DT joints can change the dynamics of the lower joint
graphic and ultrasonographic examinations centered on
tion. Surgical arthrodesis and facilitated ankyloses of
function, which can lead to the development of OA
years without lameness even in successfully working
horses. There may or may not be significant radio- within the PIT joint, which can manifest as TC effusion.
graphic signs of disease. As a primary condition, the Intra‐articular tearing of the TC joint capsule has
term “bog” should be limited to those clinical situations recently been recognized as a cause of effusion that can
in which the inciting cause of the effusion cannot be only be diagnosed arthroscpically. 5
identified. Lameness can be quite variable and often It is important to differentiate between TC effusion
depends upon the severity of the synovitis. The underly- and periarticular edema. The two may exist concurrently,
ing cause for the development of effusion includes but they may indicate different problems. Periarticular
straight hindlimb conformation (through the tarsus), edema often occurs with CL injury. Any indication that
presumably due to continuous trauma to the articular the injury is associated with the intra‐articular portion of
cartilage (Figure 5.73). Subtle OC lesions can worsen the short collateral (reported to be more common
with time and can precipitate synovitis/capsulitis and laterally) is a contraindication for intra‐articular injec-
the potential to develop OA. Horses that have mild but tions of corticosteroids (normally used for bog spavin).
clinically significant disease, especially those that require Scintigraphic examination may be considered with more
intermittent intra‐articular treatment, may eventually, acute and moderate to severe lameness when there is
and usually, become more lame as the OA advances. associated TC joint effusion. Diagnostic arthroscopy is
Many different types of pathology can produce TC indicated to evaluate the intra‐articular environment and
effusion (bog spavin). These include OC, OA (including initiate treatment when intra‐articular injection of anti‐
the TC, PIT, and DT joints), traumatic injuries (includ- inflammatories fails to resolve the effusion or the effusion
ing CL injuries and capsular tearing), poor conforma- returns after a short period of time. 5,51
tion, and infection. These will be discussed in more Many clients want their horses to have a more nor-
detail in subsequent sections of this chapter. Focal par- mal appearance of the tarsus (cosmetically acceptable).
tial‐ or full‐thickness cartilage erosions on the major Attempts to treat the swelling with HA and corticoster-
oids may have short‐lived success, but the effusion usu-
ally recurs. A support bandage can be applied to assist in
preventing of the return of the effusion. Repeated injec-
tions should be avoided. Some have reported that the
use of atropine in nonresponsive cases may have an
effect when the corticosteroids do not. There is no
known pharmaceutical mechanism of action, but 4–6 mg
is being used with noticeable success.
Diagnostic arthroscopy is a very important imaging
tool in the evaluation of the effusion of the TC joint. It
is considered the gold standard to assess the articular
cartilage is many joints, and a study by Barker et al. in
5
30 horses with soft tissue injuries found that TC arthros-
copy provided diagnostic information that was not
apparent with radiographic and ultrasonographic exam-
ination. TC joint arthroscopy also allows the direct
inspection of the intra‐articular portion of the CLs and
permits completion of necessary surgical procedures (i.e.
OC debridement). Arthroscopy is a particularly impor-
tant imaging tool for many horses with idiopathic TC
joint effusion.

OA of the TC Joint

Although uncommon, OA of the TC joint is usually
readily apparent. There is usually marked swelling of the
entire tarsus, and flexion of the tarsus is extremely pain-
ful. Radiographic examination of horses with OA of the
TC joint can demonstrate chronic changes with signifi-
cant periosteal new bone formation and enthesophytosis
of the joint capsular attachments (Figure 5.74). A complete
ultrasonographic exam is indicated in these cases to eval-
uate the periarticular tendons and ligaments, the joint
Figure 5.73. Horses with a straight limb conformation particu- capsule, and the joint fluid as well as providing valuable
larly with a straight tarsal region and a dropped fetlock appear to information about the cartilage and subchondral bone
have a predisposition for DT joint disease presumably due to surface. In the TC joint, OA tends to cause cartilage
continuous trauma to the articular cartilage. degeneration and thinning on the trochlear ridges of the