Navicular disease is a degenerative disease of the navicular bone, navicular bursa, and deep digital flexor tendon that causes varying degrees of pain in the heel region and subsequent chronic forelimb lameness. The exact cause remains unknown. The flexion test of the fetlock is the most useful diagnostic test. Hoof testers across the heel are useful but not diagnostic because 40% of most horses won't respond. Diagnostic anesthesia using palmar distal nerve blocks can confirm the diagnosis. Radiographs can support a clinical diagnosis. Other imaging modalities can aid diagnosis. Treatment involves therapeutic farriery. Regimens include raising the heels 2-4 degrees and rolling the toe of the shoe to decrease compression of the deep digital flexor tendon by the navicular bone, using a full bar shoe or pad to decrease pressure and frog trauma, and using an egg-bar shoe for under-run heels. Corticosteroid injections into the bursa or digital interphalangeal joint are only effective for synovitis and bursitis. Intraarticular hyaluronic acid can protect articular cartilage. Nonsteroidal anti-inflammatory drugs are the most used agents for pain relief and maintenance therapy and may increase circulation. Isoxsuprine HCL and pentoxifylline are two additional drugs that can help bring circulation to the distal limb. The last resort would be a palmar digital neurectomy which does not alter the disease, it only alleviates the pain.
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