Page 726 - Adams and Stashak's Lameness in Horses, 7th Edition

692 Chapter 5

inconclusive. MRI characteristics included increased T2, cation between the SCB and the ITB in about 40% of
PD, and STIR signal intensity within the LDFT in the horses’, wounds that involve point of the hock down to
VetBooks.ir LDFT injury when examined with the knowledge of the developing an infection of the ICB. Sonographic exami-
and including the SDFT should be considered at risk of
area of the TS. Ultrasonography was able to distinguish
nation typically reveals the subcutaneous position of the
MR findings. This study supports the use of MRI for
diagnosing LDFT within the TS in horses. Affected bursa and, in the early stages, a primarily fluid‐filled
horses appear to have a good prognosis for return to pocket. The fluid may have fibrin or the appearance of a
athletic performance following appropriate medical large clot within the cavity. Careful evaluation of the
treatment. ITB is critical to rule out more extensive involvement
and appropriate treatment of all affected structures.
Radiographic examination should be performed to eval-
Calcaneal Bursitis/Capped Hock
uate bony lesions.
The anatomy and nomenclature of the calcaneal bur- A capped hock appearance has been reported in cases
sae (CB) is complicated and can be confusing. The CB of gastrocnemius tendinitis and in some bony abnormal-
includes the subcutaneous calcaneal bursae (SCB), the ities of the TC 41,109 (Figure 5.95). Lameness and swelling
intertendinous calcaneal bursae (ICB), and the gastroc- in the region of the distal common calcaneal tendon are
nemius calcaneal bursae (GCB). The SCB is a poten- most commonly due to a tendonitis of the gastrocne-
113
tial bursa between the subcutaneous tissue and the mius tendon (GT). A mild to moderate enlargement of
superficial digital flexor tendon (SDFT) at the point of the ICB and a “capped” appearance can be present pos-
the TC. The SCB and ICB have also been called the cal- sibly attributable to distension of the bursa dorsal to the
caneal bursa of the SDFT. The intertendinous calcaneal insertion of the GT that may communicate with the ICB.
bursa (ICB) is further divided into the gastrocnemius LPL desmitis or curb should also be differentiated from
calcaneal bursa (GCB) and the intertendinous calcaneal swelling of the ICB and GT (see gastrocnemius tendinitis
bursa (ITB). However, these two bursae communicate in later in this section for further information).
most horses and should be considered as a single syno- Horses with signs of chronic swelling of the calcaneal
vial structure. The CB extends approximately 9–10 cm bursa should be evaluated for osteolytic lesions on the
proximally and 6–7 cm distally to the TC. The ICB is a tuber calcanei associated with the insertion of the GT
true synovial cavity analogous to the bicipital bursa and (“gastrocnemius enthesitis”). A flexed, proximoplantar
navicular bursa, and problems within this anatomic to distoplantar tangential (skyline) radiographic view of
structure are much more problematic than those within the calcaneus is advantageous for identifying this lesion
the subcutaneous bursa. However, the ICB and the GCB and is recommended for all horses with calcaneal bursi-
appeared to communicate with the SCB in 39% of tis. The prognosis for athletic soundness in horses with
limbs. chronic calcaneal bursitis and associated osteolytic
Swelling at the point of the hock (tuber calcaneus or lesions of the tuber calcanei should be considered
TC) is usually caused by damage to the SCB, giving the guarded. Well‐circumscribed osteolytic or osseous cyst‐
appearance of a capped hock (Figure 5.94). This is usu- like lesion(s) on the TC at the insertion of the GT may
ally caused by self‐inflicted trauma, typically from the be evidence of an enthesopathy or enthesitis and calca-
horse’s kicking a fixed object (wall or trailer). These neal osteitis (Figure 5.96). A US exam may reveal mild
injuries may or may not be associated with a wound. thickening of the wall of the calcaneal bursa, often dis-
The SCB at the TC is analogous to the acquired bursa at tended with anechoic fluid. The GT, SDFT, LDFT, and
the point of the olecranon. Because there is a communi- TS should all be evaluated with US.

A B C
Figure 5.94. Clinical (A) and radiographic (B) appearance of a horse with swelling at the point of the hock (capped hock). Ultrasound
(C) revealed a radiodense object within the swelling that can also be seen on the lateral radiograph (arrow).