The Lameness Examination in Small Animals
The lameness examination is a key feature to identify musculoskeletal lesions. Evaluation is performed with the animal at rest, rising, and during locomotion on flat or inclined surfaces. Single- or multiple-limb lameness is noted, with the severity related to the type of activity. With a forelimb lameness, the head is elevated during weight bearing on the unsound limb. The stride is also shortened on the affected side. For hindlimb lameness, the head is dropped during weight bearing on the affected limb. Limbs should be assessed from a distal to proximal manner, and bones, joints, and soft tissue should be palpated. Abnormalities to note include swelling, pain, instability, crepitation, reduced range of motion, and muscle atrophy. In evaluation of a subtle or obscure lameness, serial examinations before and after exercise may be necessary. For fractious animals, sedation may be required; palpation, radiography, and arthrocentesis can often be performed while an animal is sedated with IV butorphanol and acepromazine; propofol; medetomidine (alone or combined with butorphanol or hydromorphone); or a combination of ketamine, diazepam, and acepromazine.
Helpful imaging procedures to diagnose lameness include survey and contrast radiography, ultrasonography, nuclear scintigraphy, CT, and MRI. Animals undergoing these evaluations should be heavily sedated or anesthetized. Survey radiography of affected limbs or the spine requires multiple, orthogonal views. Subtle lesions are often identified after comparison with the contralateral normal limb. The most frequent contrast studies used to evaluate lame animals are arthrograms for joint diseases and myelography for spinal canal disorders. Ultrasonography is useful to evaluate musculotendinous injuries such as bicipital tenosynovitis, Achilles tendon rupture, and muscle contracture. Nuclear scintigraphy, CT, and MRI studies are usually available at private or academic referral centers. Nuclear scintigraphy involves IV injection of a radioactive compound that localizes and highlights periosseous soft tissue and bone lesions. CT imaging permits high contrast and resolution of osseous structures, whereas MRI is helpful to delineate soft tissue and joint injuries. Both can also be used to assess the spinal column, although MRI is a better standard to evaluate nervous tissues.
Arthroscopy is a minimally invasive tool used for diagnosis and therapy of lame animals. Advantages of the technique include improved visualization and diagnosis of joint pathology, ability to treat injuries by removal of damaged cartilage or ligament, and reduced surgical dissection. Disadvantages are costs of equipment and development of expertise in its use. Common conditions that can be diagnosed or treated by arthroscopy include osteochondrosis, bicipital tenosynovitis, joint fractures, and cranial cruciate ligament and medial meniscal injuries.