The most common causes of lameness in horses fall into two broad categories: hoof and foot problems, and leg or joint problems. Which one tops the list depends on the season, the horse’s discipline, and whether you’re looking at sudden (acute) lameness or chronic, progressive lameness. USDA data shows that leg and joint problems account for roughly 50% of lameness cases in spring and winter, while hoof and foot problems dominate in summer, reaching about 50% of cases. Across all categories, lameness costs the U.S. horse industry an estimated $678 million to $1 billion annually.
Hoof Problems and Acute Lameness
For sudden, severe lameness that seems to appear overnight, hoof abscesses are the single most common culprit. A survey by the American Farriers Journal found that abscesses topped the list of lameness-causing conditions among responding farriers’ horses. An abscess forms when bacteria get trapped inside the hoof, creating a pocket of infection and pressure with nowhere to escape. The result is often dramatic: a horse that was perfectly fine yesterday is now barely willing to put weight on the affected foot.
Hoof abscesses are more prevalent in wet conditions, which helps explain the USDA finding that hoof and foot problems spike in summer months, when rain-softened ground allows bacteria easier entry through the sole. Most abscesses resolve once they’re located and drained, allowing the trapped pus to exit. Recovery is usually quick, often within days, though some deeper abscesses can take weeks to fully work their way out.
Osteoarthritis and Chronic Lameness
When it comes to long-term, progressive lameness, osteoarthritis (also called degenerative joint disease) is the dominant cause. It develops when the smooth cartilage lining a joint breaks down faster than the body can repair it. Inflammation inside the joint triggers a destructive cycle: the damaged cartilage irritates the joint lining, which produces inflammatory signals that accelerate cartilage loss even further. Over time, the bone underneath the cartilage thickens and develops bony growths along the joint margins.
The joints affected most depend heavily on what a horse does for a living. Jumping horses commonly develop osteoarthritis in the fetlock joint (the large joint between the cannon bone and the pastern) because of the repeated impact forces when landing. Western performance horses tend to develop it in the hock joints of the hind legs, where sudden stops and sharp turns place extreme stress. Low-motion joints like the pastern and lower hock are especially vulnerable because they absorb concussion without much range of movement to distribute the load.
Cartilage destruction in osteoarthritis is irreversible. Once it’s gone, it doesn’t grow back. That’s why early detection and management matter so much for keeping a horse comfortable and functional over the long term.
Navicular Syndrome
Navicular syndrome is one of the most well-known causes of chronic forelimb lameness. It involves the navicular bone, a small bone deep inside the back of the hoof, along with its surrounding soft tissues. The condition typically affects both front feet, though one side is usually worse than the other. Horses with navicular syndrome often show a shortened stride, a shuffling gait, or stumbling. They may land toe-first rather than heel-first to avoid pressure on the back of the foot.
A veterinarian can often suspect navicular syndrome by pressing on the heel area with hoof testers and getting a pain response, then confirming improvement after numbing the nerves at the back of the foot. MRI provides the most detailed picture of what’s happening inside the hoof, revealing damage to soft tissues that X-rays miss entirely. Some horses show classic bony changes on X-ray, like cyst-like holes in the navicular bone or roughened surfaces, while others have significant soft tissue damage with normal-looking bone.
Management focuses on reducing stress to the back of the foot. Farriers can modify shoes to help the foot break over more easily, reducing the leverage forces on the navicular area. Anti-inflammatory medications, joint injections, and controlled exercise programs round out the typical approach. Navicular syndrome is managed rather than cured, and many horses continue working comfortably for years with consistent care.
Soft Tissue Injuries
Tendons and ligaments are another major source of lameness, particularly in sport horses. Among non-racehorses, the suspensory ligament is the most frequently injured structure, accounting for about 31% of soft tissue injuries in a large referral hospital study. The rates vary by discipline: dressage horses had the highest frequency at nearly 42%, followed by show jumpers and pleasure horses at roughly 28-29% each. Endurance and eventing horses showed similar rates.
In dressage horses specifically, the suspensory ligament was the most commonly injured structure in both the front and hind legs, with over 55% of forelimb soft tissue injuries and nearly 47% of hindlimb injuries involving this ligament. The collected, elevated movements required in dressage place sustained tension on the suspensory apparatus, which runs down the back of the cannon bone and supports the fetlock joint from dropping too low.
Suspensory injuries can be frustratingly slow to heal. The ligament has relatively poor blood supply, and returning to work too quickly is a common cause of re-injury. Rehabilitation programs typically span months, with gradual increases in exercise intensity guided by repeat ultrasound exams to monitor tissue healing.
How Veterinarians Pinpoint the Source
Figuring out which leg is lame is the first step, and it relies on watching the horse move. The most reliable sign of forelimb lameness is a head nod: the horse lifts its head and neck when the painful leg hits the ground and drops them when the sound leg lands. For hindlimb lameness, the equivalent sign is a hip hike, where the pelvis rises on the side of the lame leg during weight-bearing. Both movements are the horse’s way of shifting weight off the painful limb.
Once the lame leg is identified, veterinarians use a systematic process of numbing specific areas to narrow down the source of pain. Starting at the foot and working upward, small amounts of local anesthetic are injected around nerves or into joints. If the horse improves after a particular block, the pain is coming from the area that was numbed. This process requires careful timing, since the anesthetic can diffuse to nearby structures within about 10 minutes and blur the results. The gait needs to be reassessed quickly after each injection.
Most veterinarians grade lameness on a 0 to 5 scale developed by the American Association of Equine Practitioners. A grade 1 means the lameness is subtle and inconsistent, only noticeable under certain conditions. Grade 3 is visible at every trot. Grade 5 means the horse can barely bear weight on the limb. This standardized scale allows different veterinarians to track whether a horse is improving or worsening over time.
Treatment Options for Joint Disease
For osteoarthritis and other joint-related lameness, treatment has expanded well beyond traditional anti-inflammatory drugs. Biological therapies now play a central role. Autologous conditioned serum (sometimes called IRAP) uses the horse’s own blood, processed to concentrate natural anti-inflammatory proteins, which is then injected into the affected joint. Studies have shown it reduces lameness scores, joint swelling, and cartilage surface damage compared to untreated joints.
Platelet-rich plasma, another blood-derived product, concentrates growth factors from the horse’s own platelets. Results have been more variable than with conditioned serum, but some horses show reduced lameness and joint swelling lasting up to eight months after a single treatment. Stem cell therapy, using cells harvested from bone marrow, has shown particular promise for soft tissue injuries within joints rather than for cartilage damage itself.
For low-motion joints like the pastern or lower hock where osteoarthritis has progressed beyond the point of comfort, a procedure to fuse the joint can actually return horses to athletic work. Since these joints contribute very little to the horse’s range of motion, eliminating their movement also eliminates the pain, and the horse can function surprisingly well afterward.
Seasonal and Use Patterns
The USDA data on seasonal variation highlights something practical for horse owners. During summer months, hoof problems account for just over 50% of lameness cases, likely driven by wet-dry cycles that weaken hoof integrity and promote abscesses. In spring and winter, leg and joint problems take the lead at roughly 50%, possibly because horses are more active in training programs during those periods or because cold, hard ground increases concussive stress on joints.
A horse’s job is one of the strongest predictors of what type of lameness it will develop. Racehorses are prone to catastrophic tendon and bone injuries from high-speed work. Dressage horses develop suspensory ligament problems from collected work. Jumpers wear down their fetlock joints. Western performance horses break down their hocks. Trail and pleasure horses, while generally at lower risk, still develop navicular syndrome, osteoarthritis, and hoof abscesses at meaningful rates. Understanding these patterns helps owners and trainers recognize early warning signs before a mild problem becomes a serious one.