Clinical Examination & Imaging of the Foot

Introduction The vast majority of lameness’s that occur in the horse originate in the foot. Unfortunately the horny hoof capsule severely limits the assessment of the internal structures of the foot. Clinical examination is an essential part of any lameness examination and frequently directs the clinician to an area that is suspected as the source of pain. However, diagnostic analgesia is necessary to isolate the source(s) of pain and to more accurately direct diagnostic imaging. Interpretation of diagnostic analgesia of the foot can be difficult due to significant overlap of these blocks. Inaccuracies in analgesia techniques can also occur due to diffusion of the local anesthetic proximally along the nerve or out of the distal interphalangeal joint/navicular bursa. Diagnostic imaging becomes even more important to further define the cause of the lameness originating in the foot. Imaging techniques available to the equine practitioner include radiography, ultrasonography, thermography, nuclear scintigraphy, computed tomography and magnetic resonance imaging. To best utilize all of these imaging modalities the clinician should develop a good working knowledge of the anatomy of the foot. The clinician must also have an appreciation of the advantages, disadvantages and limitations of each imaging modality as well as the appearance of the anatomy and pathophysiology characteristic with each technique. With many of these imaging modalities it is necessary to appreciate the anatomical appearance of many of these structures in cross section, sagittal section and frontal section. With each imaging modality normal anatomical variations exist and it is important that the clinician recognize these variations as normal to prevent developing an inaccurate diagnosis. The opposite limb can and should be used for comparison when possible recognizing that disease can occur at the same location in the opposite foot. Successful management of foot lameness requires the clinician to incorporate all the information at their disposal from the clinical examination to the imaging results in order to develop an accurate diagnosis and to choose the most appropriate treatment. This paper is divided into a discussion of the normal anatomy of the foot and the imaging techniques frequently utilized to assess the foot. The discussion on imaging will highlight the advantages and limitations of the various imaging modalities in defining the normal anatomy.