IN-DEPTH: THE RELATIONSHIP BETWEEN IMAGING FINDINGS AND LAMENESS


ing. These horses have a common presentation of coming up acutely, moderately to severely lame while working and often have no soft tissue swelling or other localizing signs. The most common orien- tation of the central tarsal bone slab fracture precludes its identification on a standard four-view tarsal series, risking missing the significant diagno- sis.15 A dorsal 20–30° medial-plantarolateral oblique view is the optimal view for identifying this particular type of fracture and should always be included when the history suggests this type of injury. Bone marrow lesions (“bone bruises”) of the distal


tarsal bones will have uptake on a bone scan but require MRI to accurately localize and characterize the lesion. Horses with tarsal bone marrow lesions have variable lameness and may improve to diag- nostic analgesia of the PSL, distal tarsus, or may require a peroneal tibial nerve block. These lesions can be seen along with other tarsal changes but also can be found in horses with otherwise completely normal tarsi, likely as a result of trauma.


11. Stifle


Stifle injuries are found among all disciplines but cutting horses in particular suffer from stifle dis- ease, primarily affecting the medial femoral tibial joint. Subchondral bone defects and cysts of the medial femoral condyle found on screening radio- graphs of cutting horses have not been found to be associated with decreased performance outcome.16 However, this study had a limited number of horses with more severe condylar lesions and also lameness data were not known, therefore the long-term out- come of these changes still remains somewhat un- known and controversial. Optimally if a subchondral bone defect is identi-


fied, the horse should undergo an ultrasound to as- sess for other changes in the joint. If the joint is otherwise relatively normal without synovitis and no more than mild-moderate effusion, the defect is of questionable significance, particularly if the horse is already in work. Many working cutting horses carry some effusion in the joint and if the joint capsule is not thick and there is not synovial prolif- eration, the fluid can be incidental. Horses can have mild osteophytes of the medial


tibial condyle incidentally found on radiographs. However, further osteoarthritic changes of the me- dial femoral tibial joint including osteophytes of the axial or abaxial margins of the medial femoral con- dyle and sharp elongation of the medial tibial inter- condylar eminence are usually clinically significant findings and are uncommonly found on screening exams of sound, unmedicated horses (Fig. 4). In the author’s opinion, tears of the medial menis-


cus and medial cranial meniscotibial ligament are also rarely incidental and are typically found in con- junction with other joint disease such as synovitis and osteoarthritis. When found with articular car- tilage damage and other joint disease, the prognosis


Fig. 4. Caudo-cranial view of the stifle with severe axial and abaxial osteophytes of the medial femoral condyle, osteophyte of the medial tibial condyle, elongation of the medial tibial intercon- dylar eminence and resorption of the fossa of the medial cranial meniscotibial ligament.


for return to work lessens.17 In studies that in- cluded all or the majority Western horses, reported rates of return to full work for horses with meniscal damage ranged from 38%18 to 29%.17 Mineralization of the medial meniscus is a poor prognostic indicator and when found radiographically should be further explored with ultrasound and/or arthroscopy. Injuries to the lateral femoral tibial joint are rel-


atively rare in comparison to the medial, but can occur either in isolation or in conjunction with me- dial femoral tibial joint pathology. Effusion of the lateral femoral tibial joint is typically not seen inci- dentally and is generally suggestive of stifle pathol- ogy, either diffusely due to communication of joint pouches or originating from the lateral femoral tib- ial joint.


12. Axial Skeleton


Overall, the axial skeleton receives less attention in Western than English sport horses. Interest in cer- vical lesions is increasing but there is a dearth of information about how this is manifested specifi- cally in Western horses. Barrel horses are more likely than other Western disciplines to be assessed and treated for back prob- lems, particularly impinging spinous processes of the thoracolumbar spine.19 Impinging spinous pro- cesses are of variable clinical significance and even marked radiographic abnormalities can be clinically incidental. The combination of radiographic abnor- malities, evidence of back pain and, when possible to acquire, increased uptake on a bone scan, improves the likelihood that the changes are significant.


AAEP PROCEEDINGS  Vol. 66  2020 43


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