“No foot no horse”
The equine foot is one of the most important structures and one that frequently causes lameness issues. It is important to have knowledge of the underlying structures in order to understand the disease processes occurring in the foot.
There are three bones that are associated with the foot, the pedal bone, the navicular bone, that is similar to a pulley over which the deep flexor tendon runs and the short pastern bone. These three bones articulate within the hoof capsule. There are collateral cartilages present extending from the wing of the pedal bone. There is a joint capsule surrounding the distal interphalangeal joint and this is the articulation between the pedal bone, the short pastern bone and the navicular bone. There is also a bursa surrounding the deep[ digital flexor tendon when it traverses over the navicular bone
The bones of the foot support the horse’s weight via the bony column inside the hoof capsule, laminae attach the bones to the hoof capsule. There are several ligaments and tendons inside the hoof capsule that allow the foot to be flexed and extended.
This is a very common cause of acute onset lameness. The bruising can sometimes be very deep and affect the pedal bone and this can often take some time to resolve, treatment can be as simple as applying a poultice to the foot for a few days to applying a gel pad onto the sole of the foot to cushion the weight of the horse, along with the use of antiinflamatories. If the lameness persists then your vet will often require radiographs to ensure that there are no fractures.
This will be one of the most common conditions that we see, “puss in the foot” can be from a direct injury or from a piece of grit that has worked its way into the laminae. Although the application of a poultice can be time consuming, I think that we all are relieved when a very lame horse suddenly has a pocket of pus released. Treatment consists of releasing the infection ,irrigating the hole, and applying a poultice until the infection has been completely drawn out. This can then be followed by packing the hole with iodine and putting a pad on under a shoe once the infection has resolved.
Penetrating injuries to the foot can be life threatening and it is important to know what structures are underneath the wound. This is especially so when the wound is near the frog as the deep flexor tendon and navicular bursa are seated directly under this area. It is important to seek veterinary advice if there is any doubt as to which structures may have been involved in the case of a penetrating foot injury.
X-rays using a contrast agent that can be seen on the x-ray to delineate the coarse of the puncture may need to be used.
Treatment of a puncture to the sensitive structures of the foot will often involve using arthroscopy to flush the infected material out.
There are several soft tissue structures within the hoof capsule that are commonly associated with lameness when they are injured, one common example is a tear of the deep digital flexor tendon as it courses over the navicular bone. It is often necessary to use arthroscopy or MRI to visualise this tendon.
The bones and joints within the foot can undergo degenerative changes due to repetitive loading that is exacerbated with poor foot balance and poor training surfaces. The advent of the low field MRI has allowed visualisation of the changes seen and we now know that the well known “navicular disease syndrome” is made up of many different areas of damage within the hoof .
The joints within the hoof can also undergo degenerative change and show signs of arthritis.
Sidebone is an old term for a condition thought to be associated with foot trauma and this is seen by the collateral cartilages becoming ossified, during this process the horse can be lame but often when the ossification has stopped the horse comes sound.
Diagnosis, what to expect
Clinical examination to try to localise the area of pain often using hoof testers, increased digital pulse, visual assessment of the limb.
Nerve blocks will allow the vet to ensure that the pain is coming from the foot and may be used to more precisely locate the origin of the pain.
Treatment of repetitive strain often consists of resting the horse, reshoeing with corrective shoes and possibly the use of regenerative therapy within the joints or tendon sheaths.
The use of anti-inflamatories
Chronic foot lameness
Prevention consists of foot care and regular trimming of the feet if the feet are unshod, along with the application of protective applications such as Stockholm tar, especially useful when conditions change from dry to wet. If the cause of a lameness is more longstanding then rebalancing the foot and shoeing will be very important.