C. Wayne McIlwraith, D.V.M., director of the Orthopaedic Research Center at Colorado State University, spoke about the current state of diagnosis of equine joint disease. Early recognition is critical for both short-term and long-term soundness.
Currently, clinical examination and radiographic imaging are the most commonly used techniques for diagnosis of cartilage disease. McIlwraith mentioned that there is usually a good correlation between severity of clinical signs (lameness or joint swelling) and the amount of damage or disease found at arthroscopy.
Diagnosis of equine joint is done primarily through clinical examination, gait analysis, imaging, and biomarkers. Clinical examination is the most basic of the diagnostic tools and involves a standard lameness evaluation. Gait analysis is yet another diagnostic tool that is showing promise, but it is not at a point where it is useful from a practical perspective.
Advances in imaging, howver, have changed the way veterinarians diagnose lameness. Computed and digital radiographs are still a major focus of a lameness examination, though subtle changes are sometimes not identifiable. Computed tomography (CT) is a clinical tool used frequently, though horses must be anesthetized for this procedure to be done. CT can determine the density of bone, which may then indicate an increased propensity for fracture.
Magnetic resonance Imaging (MRI) is a sensitive and specific imaging tool for examination of hard and soft tissues. Like CT, it usually requires anesthetization unless low-field strength MRI is used. It is as good as arthroscopy for detecting subchondral lesions.
Ultrasound is still an important tool for clinical definition of osteochondritis dissecans (OCD) lesions, ligament injuries, and stifle issues, among other problems.
Nuclear scintigraphy is a sensitive, nonspecific screening technique. It is a good predictor of subchondral bone disease. It is more sensitive than MRI and arthroscopy.
Biomarkers (biochemical markers or molecular markers) measure the normal products and byproducts of metabolic processes occurring with the skeletal tissue. Biomarkers are released into the joint space and eventually into the bloodstream. Synovial fluid and serum are used as biomarkers because cartilage degradation involves destruction of the collagen framework and loss of proteoglycan products of type II collagen, and proteoglycans are liberated in increasing concentrations into the synovial fluid and ultimately the serum. Clinical studies have demonstrated the usefulness of serum biomarkers in diagnosing early joint disease, and detailing changes in osteoarthritis that can be differentiated from change in exercise.
In the most recent study done at Colorado State University, McIlwraith and coworkers analyzed serum biomarkers and indicated potential usefulness in the early prediction of intra-articular fractures, as well as stress fractures and injury to tendons and ligaments.