page_title: Lameness (equine)
section_title: Radiographs and Ultrasound
hierarchical_section_title: Lameness (equine) / Diagnostic tests / Radiographs and Ultrasound
caption_attribution_description: radiographie d'un antérieur de cheval (de profil)
context_page_description: Lameness is an abnormal gait or stance of an animal that is the result of dysfunction of the locomotor system. In the horse, it is most commonly caused by pain, but can be due to neurologic or mechanical dysfunction. Lameness is a common veterinary problem in racehorses, sport horses, and pleasure horses. It is one of the most costly health problems for the equine industry, both monetarily for the cost of diagnosis and treatment, and for the cost of time off resulting in loss-of-use.
context_section_description: The most common forms of diagnostic imaging for use during a lameness exam are radiographs ("x-rays"), to evaluate bone and joint lesions, and ultrasound, to evaluate soft tissue lesions. These modalities are best applied if the general location of lameness is known from flexion tests and nerve blocks. These methods are both non-invasive and relatively cheap.
  Radiographs ("x-rays") are made by photons, produced by a generator, that have hit a piece of x-ray film. This film is then exposed to produce an image. The photons that hit the film are actually those that have been reflected, rather than absorbed, by the animal's body. Different tissue types absorb photons to varying degrees, leading to differing levels of darkness (radiodensity) on the x-ray film. An anatomical structure is delineated by comparing its radiodensity those tissues surrounding it. Interpretation of a radiograph therefore requires the surrounding structures to have enough of a difference in radiodensity to allow it to stand out. While this is obvious in tissue such as bone, soft tissues of the leg do not stand out well on radiographs. Therefore, radiographs are best used to evaluate boney changes rather than soft tissue damage. One exception of this rule is the use of contrast, injected into synovial structures, which allows these structures to stand out on radiographs. Common uses for radiographs are to evaluate for suspected fractures, bone chips, laminitis, and navicular changes.
  Ultrasound measures the reflection of high frequency sound waves off of tissues. Different tissues absorb or reflect ultrasonic waves to different degrees, which may be picked up by the machine and turned into an image. Because ultrasound does not easily cross bone or air, it is best used for the evaluation of soft-tissue structures. It is therefore a complementary imaging modality to radiographs, and is most commonly used to look for injury to ligaments and tendons, and the navicular bursa, although muscle damage and arterial blood flow have also been evaluated with ultrasound in cases of lameness.  Ultrasound is especially useful for determining the size and shape of lesions within structures, allowing quantification of an injury. Ultrasound may be used after diagnosis, to monitor the progression of healing of a lesion. It is also used to guide injections of treatments (steroids, stems cells, platelet rich plasma) directly into a lesion.
caption: Radiographs are commonly used to evaluate lameness in the lower limb.
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