Overview of Lameness in Small Animals

Lameness (altered gait, such as altered weight bearing, shortened stride, stiffness, or reluctance to move) is a key clinical sign of musculoskeletal disease. Other clinical signs of musculoskeletal disorders include pain, limb swelling, and joint dysfunction.

By definition, lameness arises from pain or dysfunction of the musculoskeletal system. Although many musculoskeletal disorders can cause an abnormal gait, they do not typically cause ataxia. If the patient demonstrates ataxia, abnormal proprioception, or abnormal spinal reflexes, a neurological component to the disease should be investigated.

Occasionally, musculoskeletal abnormalities in small animals are associated with concurrent systemic disease. For example, dogs with chronic high levels of endogenous steroids (such as with unmanaged or poorly managed Cushing disease) might have joint laxity of the carpi, tarsi, or other joints. Inflammatory diseases, such as immune-mediated polyarthropathy, can also result in joint abnormalities. Until the underlying disease is addressed, the orthopedic conditions cannot be resolved.

Musculoskeletal disorders in small animals can also be related to urinary or GI disordersthat cause calcium and phosphorus imbalances or thoracic or extrathoracic masses that lead to hypertrophic osteopathy or lung-digit syndrome.

Evaluation of musculoskeletal disease is aimed at localizing and defining lesions. Diagnosis requires accurate review of the patient's signalment and history, as well as thorough physical and orthopedic examination.

Orthopedic examination typically involves gait evaluation, standing examination, and recumbent examination. For more complete evaluation of the patient or for patients that are not amenable to an awake examination (such as aggressive or anxious patients), sedated examination can also be helpful.

Useful ancillary tests include radiography or ultrasonography (see Diagnostic Imaging) and arthrocentesis. Fluid obtained from arthrocentesis should be submitted for fluid analysis and culture. Fluid analysis enables identification of abnormal cell numbers or cell types within the joint, and culture helps to identify the presence of bacteria. However, a culture-negative result does not completely rule out joint infection.

Advanced diagnostic imaging techniques such as CT and MRI are increasingly used in referral and university teaching hospitals. Diagnostic arthroscopy can also be used for more complete evaluation of articular surfaces and intra-articular structures.

If needed, samples of the synovium or other articular structures can be obtained for histological evaluation and/or culture.

Arthrography (placement of contrast into the joint) is not often performed anymore, because of the availability of advanced imaging; however, it might be an option for further evaluation of articular structures if other diagnostic tests are not available.

Bone scan (nuclear scintigraphy) is also not often performed; however, it might be a reasonable option to help identify abnormalities that are difficult to localize.

A brief neurological examination can be performed to help differentiate between musculoskeletal and neurological disorders. Electromyography can also be used to help differentiate between the two body systems.