Are limb deformities a common problem in foals?
Yes, a very high percentage of foals are born each year with crooked legs or limb deviations/deformities.The main reason is that foals have disproportionately long legs and these elongated limbs often appear crooked. These deformities or Angular Limb Deviations (ALD), are due mostly to ligament laxity and muscle weakness.In the majority of cases, nature ensures that the legs will eventually straighten.However, in some cases additional factors are involved and the limbs may fail to improve. If the deformity is mild, it may only be an insignificant conformational fault. But if it is severe then it may compromise the foal’s future athletic potential.Horses are bred to be athletes therefore the straightness of their limbs and the placement of their feet are important, to avoid joint problems, lameness and premature retirement. Are (ALD) limb deviations in foals usually acquired or are they born with them?
a) Congenital limb deviations are the commonest form, i.e. foals have them at birth.
b) Acquired: Some of these limb problems can also be acquired i.e. they develop during the foal’s growth/development for various reasons such as unbalanced nutrition, excessive exercise and/or trauma, etc.
What are the most common causes of (ALD) limb deviations in foals?
Congenital limb deviations can be due to under-developed bones and/or ligaments such as incompletely ossified hock bones, e.g. in the case of premature foals, with long weak hind legs, ligament laxity and muscle weakness which will usually correct itself as the foal exercises. Once the bones have fully formed/calcified, an angular limb deformitiy will result, due to the abnormally shaped knee bones.Other factors may also cause the problem, such as premature birth, twin pregnancy, placentitis, perinatal soft tissue trauma and flaccidity of the soft tissue structures surrounding the joints.a) Acquired limb deviations can be due to a multitude of circumstances, all of which cause an unbalanced rate of growth longitudinally.
These causes include nutritional imbalances, trauma, infection, exercise, altered loading /balance of the limb, etc. If the knee bones are not fully formed they run the risk of being crushed from exercise and the uneven load that is placed on the joint. How are angular limb deformities (ALD) diagnosed?
As early diagnosis is all important, it is essential to call in a veterinary surgeon with expertise in the area of foal conformation, to assess these foals at an early stage. It is common practice on stud farms to examine all foals regularly on a flat hard surface and walk them up and down to assess limb conformation, footfall and break-over.This enables any tendency towards angular limb deformities to be picked up and corrected early, by means of corrective trimming or farriery. A slight adjustment of the balance of the feet, if carried out at an early stage, can keep limbs growing straight and true. It is significantly easier to correct limb deviations at the foal stage than at the yearling or later stages.The assessment is done by viewing and walking the foal on a flat level non-stoney yard surface – concrete or tarmacadam is acceptable provided it is not slippery.What does the term `angular limb deformity’ (ALD) mean or indicate?
Basically the term angular limb deformities (ALD) refers to a deviation of the limb either outward (lateral) or inward (medial) from below a certain reference point, typically at a joint.Limb deviations in foals may be divided into two types: a) Angular limb deformities (ALD), where the limb appears angled or crooked when viewed from in front or behind.
b) Flexural ALD contractures, where the leg has a flexed or folded appearance when viewed from the side.
What are the common types of ALD limb deviations in foals?
There are two terms used to describe the most commonly occurring types of limb deviations : A varus ALD deviation refers to a horse which is typically toed-in, versus a valgus ALD deviation, which refers to a horse which is typically toed-out. Deviations from the knee are the most common, followed by the fetlock and hock. Very often more than one limb is involved.The most common ALD deviation seen in young foals is in outward deviation from the knee in one or both of the front limbs. This ALD is called carpus valgus. The foal appears splay-legged, with the knees kinked inwards and the cannons pointing outwards more than the forearms. Could some slight ALD deviations be normal in certain types of foals?
Yes, some very slight carpal valgus is considered normal in young foals and will not completely resolve until the chest widens and the forearms are pushed outwards. A deviation may be toed-in, or toed-out but most foals are born with an outward deviation of the front limbs. This usually starts at the knees. In foals this is considered acceptable as in most cases they correct themselves - unless it is a very extreme form of deviation.Which joints are most commonly involved in ALDs?
The most commonly seen deviations are:a) From the knee
b) From the fetlock
c) From the hock
Deviations from the fetlock are less likely to correct themselves without some intervention.If the knock-kneed appearance is simply due to slack, floppy ligaments in the knee (the “carpus”), the legs will straighten as the foal moves and strengthens. Foals born with deviations inwards or ‘bandy’ legs do not usually correct themselves. This type of limb deviation is an abnormality and will usually require intervention in order to correct them. Very commonly foals are born with flexural deformities - fetlocks either too low or too high - or knees slightly flexed. These almost always correct themselves.
Although carpal valgus is common, angular limb deformities also happen at the fetlock, where an inward deviation is seen most often - a fetlock “varus” deformity. The hock may also be affected e.g. often referred to as a “wind swept” foal, and although it may be just as common, it seems to lead to fewer problems if it remains uncorrected.