Joint disease is one of the most common causes of lameness and performance limitation in horses. Osteoarthritis (OA, also called degenerative joint disease or DJD) involves progressive degradation of articular cartilage and associated joint structures. Navicular syndrome (palmar foot pain, podotrochlosis) is a specific and frequently diagnosed cause of forelimb lameness involving the navicular bone and associated soft tissues of the heel region. Both conditions require multimodal management combining pharmacological treatment, corrective farriery, and exercise modification.

Overview

Equine joints endure enormous biomechanical forces during athletic activities. The high-motion joints (fetlock, carpus, hock) are most commonly affected by OA, while the coffin joint and navicular apparatus are the primary sites of navicular syndrome. Articular cartilage in horses has limited capacity for self-repair, making early intervention and ongoing management essential to preserving function and comfort.

Navicular syndrome encompasses a spectrum of pathology including navicular bone degeneration, navicular bursa inflammation, deep digital flexor tendon damage, and coffin joint disease. Modern imaging has revealed that what was once considered a single entity is actually a complex of related conditions.

Causes & Risk Factors

  • Repetitive concussive forces — Athletic horses in jumping, dressage, racing, and barrel racing are at highest risk
  • Conformational faults — Long toes/low heels, upright pasterns, and base-narrow conformation predispose to specific joint problems
  • Age — OA prevalence increases with age, though young performance horses also commonly develop joint disease
  • Previous joint injury — Chip fractures, ligament injuries, and joint infections can accelerate OA development
  • Excessive body weight — Increases mechanical stress on joints
  • Improper hoof balance — Poor trimming and shoeing contribute to navicular syndrome and coffin joint disease
  • Breed predisposition — Quarter Horses and Thoroughbreds may have higher rates of navicular syndrome

Symptoms

  • Lameness (may be intermittent initially, worsening with work)
  • Stiffness, especially after rest (“warming out of it” early in exercise)
  • Shortened stride length
  • Reluctance to turn sharply or work on hard surfaces
  • Shifting lameness between legs (with bilateral navicular disease)
  • Joint effusion (visible or palpable swelling)
  • Decreased performance or reluctance to jump
  • Positive response to flexion tests
  • Pointing a forelimb at rest (navicular syndrome)
  • Stumbling or toe-dragging

Diagnosis

  • Lameness examination — Observation at walk and trot, flexion tests, hoof testers, and response to exercise on different surfaces
  • Diagnostic nerve blocks — Sequential regional anesthesia (palmar digital, abaxial sesamoid, low/high four-point) to localize pain
  • Radiographs — Baseline imaging of affected joints; may show joint space narrowing, osteophytes, subchondral bone changes, or navicular bone remodeling
  • Ultrasound — Evaluates soft tissue structures including tendons, ligaments, and joint capsule
  • MRI — The gold standard for navicular syndrome diagnosis; reveals soft tissue, bone, and cartilage pathology not visible on radiographs. Available as standing low-field or general anesthesia high-field MRI.
  • Diagnostic joint injection — Temporary improvement after intra-articular anesthesia confirms the joint as the pain source
  • Nuclear scintigraphy (bone scan) — Identifies areas of active bone remodeling in horses with multiple limb lameness

Treatment & Medications

Systemic Medications

  • Phenylbutazone (Bute) — The most commonly used oral NSAID in equine practice. Effective for musculoskeletal pain. Long-term use requires monitoring for GI ulceration and kidney effects. Typical dose: 2.2 mg/kg orally twice daily, reduced to the lowest effective dose.
  • Firocoxib (Equioxx) — A COX-2 selective NSAID with potentially fewer GI side effects than phenylbutazone. FDA-approved for equine use as a paste or tablet. Useful for chronic daily management.
  • Adequan (polysulfated glycosaminoglycan, PSGAG) — An intramuscular disease-modifying agent that inhibits cartilage-degrading enzymes and supports cartilage metabolism. Standard protocol: 500 mg IM every 4 days for 7 treatments, then monthly maintenance.
  • Hyaluronic Acid (Legend, IV formulation) — Intravenous hyaluronic acid provides anti-inflammatory effects throughout all joints. Given as a series of treatments.

Intra-Articular (Joint Injection) Therapies

  • Corticosteroids — Triamcinolone acetonide (preferred for high-motion joints, considered less harmful to cartilage) or methylprednisolone acetate. Provide potent anti-inflammatory effects. Typically repeated no more than 2-3 times per year per joint.
  • Hyaluronic acid — Often injected in combination with corticosteroids to improve joint lubrication and reduce inflammation.
  • Pro-Stride / IRAP (autologous conditioned serum) — Biologic therapies using the horse’s own blood products to deliver concentrated anti-inflammatory proteins (IL-1 receptor antagonist) directly into the joint.
  • PRP (platelet-rich plasma) — Concentrated growth factors to promote tissue healing within the joint.
  • Osphos (clodronate) or Tildren (tiludronate) — Bisphosphonate drugs that inhibit bone resorption. FDA-approved for navicular disease. Osphos is given as a single intramuscular injection; Tildren as an IV infusion or regional limb perfusion.
  • Corrective shoeing — Egg-bar shoes, wedge pads, or rocker-toe shoes to improve breakover and reduce stress on the navicular apparatus
  • Isoxsuprine — A vasodilator historically used for navicular syndrome, though evidence for efficacy is limited
  • MRI-guided treatment planning — Tailoring treatment to the specific pathology identified on MRI

Prognosis

  • Mild OA managed early with multimodal treatment can allow years of continued athletic use
  • Advanced OA with significant cartilage loss carries a more guarded prognosis for return to previous performance levels but can often be managed for comfort
  • Navicular syndrome prognosis depends on the specific structures involved; soft tissue lesions may respond better to treatment than advanced bone changes
  • Horses with navicular syndrome managed with bisphosphonates and corrective shoeing often show significant improvement
  • Joint disease is progressive; the goal of treatment is to slow progression, manage pain, and maintain quality of life
  • Retirement to light work or pasture may be necessary for horses with advanced disease

Frequently Asked Questions

How often can my horse’s joints be injected? Most veterinarians recommend no more than 2-3 intra-articular corticosteroid injections per joint per year. Biologic therapies (IRAP, Pro-Stride, PRP) may be repeated more frequently. Your veterinarian will develop a schedule based on your horse’s specific needs and response.

Is Bute safe for long-term use? Phenylbutazone can be used long-term at the lowest effective dose, but it carries risks of GI ulceration, kidney damage, and right dorsal colitis. Firocoxib (Equioxx) may be a safer alternative for daily use. Concurrent use of omeprazole or other gastroprotectants may be recommended.

What is the difference between Adequan and Legend? Adequan (PSGAG) is given intramuscularly and works primarily by inhibiting cartilage-degrading enzymes. Legend (hyaluronic acid) is given intravenously and works primarily as an anti-inflammatory and joint lubricant. They have complementary mechanisms and are sometimes used together.

Can navicular syndrome be cured? Navicular syndrome is typically managed rather than cured. Many horses achieve significant improvement and return to comfortable work with a combination of corrective shoeing, bisphosphonates, and other therapies. However, the underlying structural changes are generally not reversible.

This information is for educational purposes only and does not replace professional veterinary advice. Consult your equine veterinarian and farrier for diagnosis and management of your horse’s specific condition.