The Horse

DEC 2018

The Horse:Your Guide To Equine Health Care provides monthly equine health care information to horse owners, breeders, veterinarians, barn/farm managers, trainer/riding instructors, and others involved in the hands-on care of the horse.

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30 December 2018 The Horse | Armed with the basics, here are the common questions regarding OA in horses you said you needed answered at Q How can I gauge my arthritic horse's pain levels? This is a fantastic question because OA's prevailing clinical sign is pain manifesting as lameness. The most com- mon method of assessing lameness is a veterinary lameness exam, generally us- ing the American Association of Equine Practitioners' lameness scale, as well as flexion testing and anesthetic blocks (regional or in the joint, if possible) to accurately determine the site of pain. Radiographs (X rays) reveal typical OA lesions, but none might be evident in the early stages because cartilage is not vis- ible on radiographs. Horses with mild OA often appear stiff when emerging from the stall or starting work before warming up and looking more comfortable. More severe signs include swelling, heat, and persistent lameness, which can preclude comfort and athleticism. To complicate the situation, OA is one of those conditions that people tend to assume a horse has simply because it's so common. However, deciding a horse has any medical condition and treating it without consulting a veterinarian can have serious consequences, delay ap- propriate treatment, and drain valuable owner resources. "Assuming a horse is suffering from OA can be dangerous, as there are actu- ally several other conditions that present similarly to lameness associated with OA," warns Laverty. "The list is long and can (include) a variety of conditions af- fecting the bones and soft tissues." Q How can I keep my arthritic horse comfortable? Currently, options for managing pain in horses with OA remain limited, even though a plethora of pharmaceutical and nonpharmaceutical options exist. Com- mon pharmaceutical approaches include: 1. Non-steroidal anti-inflammatory drugs such as phenylbutazone (Bute) admin- istered by mouth, usually daily; or 2. Injectable products that contain hyaluronic acid or polysulfated-based active ingredients such as polysulfated glycosaminoglycan (PSGAG) and pen- tosan polysulfate sodium (PPS). Recently, Laverty and colleagues dove deeper into how OA causes pain and lameness. "While it may be difficult to impossible to differentiate clinically, pain can actu- ally be classified as one of three broad 'types,' and each appears to contribute to the pain associated with OA," she says. Those three types include: 1. Nociceptive pain, which is caused by activation of pain receptors in the joint secondary to abnormal movements as- sociated with OA. 2. Inflammatory pain, resulting from the release of inflammatory mediators that impact a variety of surrounding joint tissues. Inflammatory media- tors can also "prime" the nociceptive pain receptors in joint tissues, making them more sensitive than normal and increasing pain levels. 3. Neuropathic pain, caused by damage to specific regions of the horse's nervous system that perceive pain. "In the past, we assumed that the pain associated with OA was primarily noci- ceptive in nature, but we now appreciate that to adequately control the discomfort associated with OA, all three types of pain may need to be addressed," Laverty says. "It is fascinating that the exact tissue source of the pain sensation is unknown in the case of OA," she adds. "Articular car- tilage does not have nerves, whereas the soft tissues such as ligaments and synovial membranes and bone are innervated." While researchers continue to search for better pharmaceutical treatment op- tions for OA, owners often elect to pursue nonpharmaceutical approaches. Joint supplements and other options (which we'll discuss in more detail) remain popular, though researchers on several recent studies emphasize the importance of addressing weight management. The number of overweight and obese horses mirrors the obesity epidemic in humans and other companion animals. In a recent study Canadian researchers reported that approximately one in three domestic horses is considered not just overweight, but obese. Erin Contino, MS, DVM, Dipl. ACVSMR, of Colorado State University's Orthopaedic Research Center, in Fort Collins, says data generated in human Equine Osteoarthritis SHELLEY PAULSON Intra-articular corticosteroid injections remain the cor- nerstone for managing joint disease in horses. Because OA is comparable among dogs, humans, and horses, similar benefits associated with weight loss and OA would be expected in horses." DR. ERIN CONTINO

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