Laminitis (also known as founder) can strike fear into the heart of horse owners. Laminitis means inflammation of the laminae (the connective tissue "glue" that attaches the coffin bone to the hoof wall- bright red in the attached picture), which can then lead to rotation or sinking of the coffin bone as pictured. Because all of your horse's weight is essentially carried by the coffin bone, when the laminae become weakened the toe of the coffin bone is forced down by gravity. As you can imagine, this is extremely painful to the horse, and failure to control the pain and stop the progression of this disease may ultimately result in euthanasia.
There are many causes for laminitis, but the main ones include: 1. Mechanical a) repetitive trauma from hard surfaces ("road founder") b) inability to bear weight on an injured limb and overloading the opposite (supporting) leg 2. Toxin (such as black walnut mixed in shavings) 3. Endotoxemia, caused by severe inflammatory illnesses (Potomac Horse Fever, Salmonella, colic, grain overload, retained placenta) that cause the gastrointestinal wall to be inflamed and allow bacteria from the gut to release toxins into the bloodstream, which travel to the feet and cause severe inflammation of the laminae 4. Endocrine (hormonal imbalance) diseases such as Cushing's or Equine Metabolic Syndrome that cause high cortisol and insulin resistance(similar to type 2 diabetes), which damages the laminae
Signs of laminitis include leaning back to take weight off the front feet (more commonly affected than hind feet because they bear more weight), increased digital pulses, heat in the foot, lameness, constant weight-shifting, or even reluctance to walk.
Your veterinarian can use hoof testers to see if the horse is sensitive to pressure at the toe, and may take radiographs (x-rays) to evaluate the degree of rotation and/or sinking of the coffin bone. In the pictured radiograph the hoof wall and front part of the coffin bone are not parallel, and the toe of the coffin bone is very close to the bottom of the sole (coffin bone rotation). Based on the severity of disease, different management options may be pursued, often with cooperation between your farrier and veterinarian.