Oct. 24, 2018
Joint Injuries and Therapy
By Jennifer Dunlap, DVM
Lameness is the number one cause of poor performance in sport horses. Horses, like all athletes, face wear and tear on their bodies. This can manifest as muscle soreness, soft tissue injuries involving tendons and ligaments, and as bone and joint injuries. Joint injury accounts for a large percentage of lameness in performance horses. The good news is there are a lot of things we can do to help prevent and to treat joint injuries.
Some joints have a wide range of motion, such as the upper hock joint and the tibiotarsal joint, and some have very low motio, such as the three lower hock joints. While some joints contain only a fibrous (think tough saran wrap) tissue attachment, the major joints involved in joint injuries are made of bone covered in cartilage with a fibrous joint capsule wrapped around the joint, which contains thick joint fluid with supporting ligaments around, and sometimes inside, the joint. The cartilage and the joint fluid provide shock absorption and smooth gliding function. The ligaments provide support keeping the joint from moving too far one way or the other. The joint capsule is elastic in a healthy joint and it helps stabilize the joint and provides a seal for the joint.
Joint injury can range from acute (sudden) injuries to injury due to chronic wear and tear over time. Injuries can also range from mild to life threatening. The majority of joint injuries seen outside the racehorse world involve chronic wear and tear injuries, which cause arthritis. When a joint is inflamed, inflammatory chemicals rush into the joint, the joint fluid volume increases while becoming less thick, so is less supportive of the joint, and the joint capsule is stretched due to increased fluid. This all leads to pain and lameness. Mild joint injuries involving just inflammation will generally resolve quickly with the right care on the farm, which generally includes rest, bandaging and cold therapy in the form of an ice boot or water hose. A step up from the acute mildly inflamed joint is an acutely injured joint that involves mild cartilage damage, mild supporting ligament damage, and/or joint capsule tearing. These injuries may require prolonged periods of rest, intra-articular (into the joint) medications and surgery. A severely injured joint can occur in catastrophic breakdown injuries in which bones are broken, cartilage is crushed and ligaments are torn. These require hospitalization and surgery in order to save the horse’s life. These injuries are most commonly seen in racehorses, but occasionally are seen in the rest of the horse world in high speed sports and in freak accidents.
Joints can also be severely damaged if a wound enters a joint because it causes immediate inflammation and infection. It is a “red alert” emergency any time a wound is found around a joint, and your veterinarian should be called immediately to make sure the joint is not involved in the wound; because the longer the joint is infected, the more severe the damage to the joint. Septic (infectious) arthritis can set in very quickly as the infection and the inflammatory chemicals damage the cartilage, the underlying bone, and the joint capsule. Septic joints require aggressive treatment with antibiotics, both systemically (generally intravenous, IV) and directly into the joint or the affected limb and joint, flushing to remove the infection and inflammation. Arthroscopy can be used to flush the joint with a high volume of fluid, diluting out the infection and inflammation, and to remove affected portions of the damaged joint capsule and cartilage.
Generally, the majority of joint issues involve chronic wear and tear injury leading to arthritis. It is important to remember that arthritis is due to mileage placed on a joint, not the years. While arthritis can certainly develop due to very advanced age as the surrounding muscles and ligaments become less supportive of the joints, the majority of arthritis is due to usage. This is the reason why we can see significant arthritis in a heavily raced two-year-old racehorse, and joints that are as clean as a whistle in a lightly ridden twenty-year-old horse.
Signs of arthritis can include reduced range of motion in a joint, seen as less flexibility as the joint capsule becomes thicker and less flexible; loss of smooth gliding function due to thinning of the cartilage; and weakness of the ligaments, leading to lameness or short stridedness. Radiographically we might see reduced joint space due to cartilage thinning and osteophytes (bone spurs) on the edges of the joint. Spurs are generally due to bony growth in response to microtearing or inflammation at the joint capsule attachment or soft tissue attachments around the joint.
So where’s the good news in all this? 1. The majority of horses handle mild arthritis when good care is in place, just like people do. It would be unheard of for human or animal athletes to go through their careers without developing some level of arthritis. What matters is how you maintain as an athlete. Athletes kept fit and in good shape can do very well with mild arthritis. 2. There are things we can do to help prevent and to treat arthritis/joint disease.
Preventive measures. As a sport horse breeder, rider, and veterinarian, I have found there are a lot of things we as horse owners can do to help our horses stay fit and sound. If you are in the market for a horse look for one “built” (with the conformation) to do your chosen sport. There is obviously no perfectly conformed horse out there, and courage and work ethic are always factors. But a horse with the conformation and movement to do your sport will put less wear and tear on his joints than one who is not really conformed for the job at hand. For example, I wouldn’t expect my draft horses to barrel race with any speed or grace.
Working youngsters too much or too young can be very detrimental to their bones and joints; this is where the mileage statement comes in. Some do not have the muscular, ligamentous or skeletal strength or the balance for hard work at a young age. Some breeds, including Warmbloods and drafts, are still growing well into their five- and six-year-old years.
It is critical to warm up and cool down slowly, allowing the supporting structures of the joint to stretch and flex so they can better support the joint they are stabilizing to help prevent joint wear and tear.
It is also critical to make sure your horse is fit enough to do the job asked of him. While we can’t strengthen a joint, we can strengthen the muscles, ligaments, bones, and tendons through good fitness exercises, which will, in turn, support the joint. Joint injury is much more common when a horse is fatigued. Joints can hyperextend; a misstep can occur or ligaments and muscles can fatigue. If you look at the fetlock extension in a race horse at the beginning of a race, versus the angle of extension near the finish line, the extension of the fetlock is much more marked at the end of the race.
Cross training has long been a buzzword in human athletics and it can also be used for horses to increase strength and fitness. Think of it this way: a football player doesn’t just play football to stay fit enough to play football. They run, lift weights, and stretch to stay fit for football. Horses need strength, flexibility, and aerobic fitness for most of the jobs we ask them to perform. For example, walking up and down hills can be extremely beneficial for hind end strengthening, and riding outside an arena can be a physical and mental break for equine athletes. A former Olympic dressage rider takes his dressage horses out to jump over little logs and ditches for both the mental break and for building up muscles and strength while doing a different activity.
Finally, pay attention to your horse’s legs. Never ignore a bit of swelling, heat or slight lameness as this can be a sign of an impending problem and if caught early less treatment may be required.
Oral Supplements and IV/IM medications: There are many joint supplements on the market and many contain varying levels of chondroitin sulfate and glucosamine, both components of cartilage. Others contain hyaluronic acid, the part of joint fluid which makes it thick and cushiony. MSM is also a common joint/anti-inflammatory supplement thought to work by providing sulfur for healthy collagen development. Duralactin contains a milk derivative protein that is targeted at relieving inflammation.
Oral joint supplements are not a big bang for your buck, but they can be helpful. There are some excellent human and equine studies which have shown some benefit from the above mentioned compounds in helping reduce arthritis pain.
Systemically injected medications available for joint injuries include Adequan and Legend and their respective generics, and are aimed at reducing inflammation and promoting healthy joint fluid in multiple joints. Adequan is administered in the muscle (IM) and contains polysulfonated glycosaminoglycan. Its claims to fame are that it promotes production of hyaluronic acid, inhibits destructive inflammatory enzymes, is cartilage protective, and will reduce inflammation in the joints. Legend, is an intravenous (IV) injectable form of hyaluronic acid.
Intra-articular (into the joint ) therapies: Joint injections are the biggest tools we have to treat arthritis and some acute joint injuries. They are far and away the best choice for horses with arthritis in one to a few joints. Joint injections place medications directly into the affected joint or joints and are usually a steroid, hyaluronic acid, or a combination of the two. Steroids are the most powerful anti-inflammatory available and the hyaluronic acid can provide cushioning and cartilage protection. Joint injections must be used judiciously though! They should only be done if a horse is sore in that joint. They should never be used as preventive measures or as part of a “show prep” program, because if there is no inflammation in the joint, it is being injected for nothing and the medications are not preventive in nature.
In recent years a new tool called IRAP has joined the ranks of joint therapy. IRAP is Interleukin-1 Receptor Antagonist Protein therapy. It can be used to treat mild to moderate arthritis and acute synovitis (acute joint inflammation). It is an alternative to steroid injection and works by blocking Interleukin-1, the main chemical involved in damaging cartilage in arthritis. The IRAP system is designed to stimulate the horse’s own white blood cells to produce anti-inflammatory chemicals that reduce inflammation in the affected joint. The therapy involves drawing blood from the affected horse, incubating the blood in special syringes, then spinning the blood and drawing off the enhanced serum. The serum can be frozen and injected into the joint at a later date.
As horse owners, the goal is to keep our horses sound, healthy, and happy. Paying attention to your horse’s fitness level and care, and catching injuries early, can go a long way in achieving that goal.
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