Page 759 - Adams and Stashak's Lameness in Horses, 7th Edition

Lameness of the Proximal Limb 725

THE STIFLE: FEMOROTIBIAL JOINT REGION

VetBooks.ir Chris KawCaK

The medial femorotibial (MFT) and lateral femoroti- done by keeping the tarsal area as straight as possible
bial (LFT) joints are separate structures that usually lack and bringing the limb caudally from the tibia distally
physical communication except in cases of severe osteo- (Figure 2.108). A positive response to this flexion is not
arthritis (OA) and cruciate ligament damage and occa- absolutely indicative of stifle pain, but it can give impor-
sionally after arthroscopy in which the septum separating tant information about the site of pain.
the two structures was perforated. The MFT joint usu- More severe cases of lameness attributable to the sti-
ally communicates with the femoropatellar joint through fle are often obvious on clinical examination due to
a fenestration in the proximal aspect of the joint. This is severe effusion, soft tissue swelling, pain on palpation,
important from the standpoint that disease in the MFT and severe response to flexion. However, diagnostic
joint can manifest as femoropatellar joint effusion, anesthesia is needed to confirm the site of pain in many
sometimes leading to confusion about the true site of horses. The approach to diagnostic anesthesia of the sti-
damage, since diagnostic anesthesia of one joint can fle can be complex. Intra‐articular pain in one joint can
influence the other. Consequently, heavy emphasis is be improved with anesthesia of the other joints, but the
placed on diagnostic imaging and sometimes arthros- response is much better in the joint of pain. Some clini-
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copy to resolve the confusion. cians block all three joints of the stifle at once to expe-
Both MFT and LFT joints are each composed of a dite the process, rather than starting with one joint and
femoral condyle and tibial plateau and a meniscus then blocking the other joints. Single‐needle technique is
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between the two. A soft tissue septum separates the two preferred by the author. Consequently, if all three joints
compartments, which continues caudally to surround are blocked at once, the clinician may need to further
the cranial and caudal cruciate ligaments, making these isolate the joints later to determine which ones contrib-
structures extrasynovial in this location. The same is ute to the lameness.
true for the medial and lateral collateral ligaments. Regardless of how stifle pain is confirmed in affected
Horses with lameness originating from the femoroti- horses, accurate imaging of the joints is difficult.
bial joints can vary in severity. Some cases are subtle Improvements in radiography, ultrasound, computed
enough to create a training issue without the presence of tomography (CT), and magnetic resonance imaging
noticeable lameness, whereas others are severe enough (MRI) have helped to characterize the disease processes,
to lead to non‐weight‐bearing lameness. In more severe but the lack of visualization during arthroscopic surgery
and chronic cases, horses typically stand with the limb and a minimal number of postmortem studies have pre-
abducted, and there is usually noticeable atrophy of the vented investigators from truly correlating imaging
hip and quadriceps musculature. results to gross damage. Unlike other species, the femo-
Whereas effusion in the LFT joint is difficult to pal- rotibial joints in the horse are closely packed, preventing
pate, effusion of the MFT joint is readily palpable, arthroscopic visualization of most of the joints.
especially in the recess just cranial to the medial collat- Consequently, the ability to truly characterize and repair
eral ligament and proximal to the meniscus and tibial damage in many parts of the femorotibial joints is
plateau (Figure 2.91) However, in more severe and limited.
chronic cases, significant soft tissue thickening can also Diagnostic imaging has been well described in this
occur in this area, often obscuring the ability to palpate text and others. Radiography has been most relied upon
effusion. This is referred to as a tibial buttress and is for characterization of bony changes in the joint, and the
usually associated with advanced OA within the joint. importance of proper positioning cannot be emphasized
The degree of effusion and swelling is usually graded as enough. There is recent evidence to show that joint space
normal, mild, moderate, or severe, and any pain and width can be accurately measured and followed with a
thickening of the collateral ligament is noted. properly performed caudoproximal to craniodistal
There are no distinguishing characteristics to limb oblique projection made at 10° from horizontal.
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use in horses with stifle pain compared with those with Diagnostic ultrasound is routinely used to assess lame-
pain at other sites in the hindlimb. All horses should be ness localized to the stifle and is helpful for characteriz-
walked and trotted in a straight line. Subtle lameness is ing meniscus and periarticular damage. However, it is
sometimes more noticeable in soft footing, especially limited compared to arthroscopic surgery for character-
when horses are jogged in a circle. Although most horses izing articular cartilage and cranial meniscal ligament
are more lame when the limb is on the inside of the cir- damage. Nuclear scintigraphy is moderately specific but
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cle, occasionally the lameness is worse when the limb is insensitive for characterizing stifle lesions. Computed
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on the outside of the circle. Observing the horse under tomography has demonstrated good correlation to radi-
tack or in work can also improve characterization of the ography and ultrasound for detection of osteophytes in
lameness. cadavers. However, in a prospective clinical study,
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Horses with stifle pain are typically responsive to full Nelson et al. demonstrated better characterization of
limb flexion. However, some information can be gained cruciate disease, entheseal changes, and proximal tibial
by attempting to isolate flexion to the stifle area. This is changes using CT and CT arthrography compared with