Toby Kemble BVetMed MRCVS,
Wensum Valley Veterinary Surgeons
Angular limb
deformities in foals
11
EQUINE MATTERS
L IMB DEFORMI T I ES
Veterinary surgeon
Toby Kemble
XLEquine practice
Wensum Valley
Veterinary Surgeons
Angular Limb Deformity (ALD) is the name given to a series
of problems encountered in newborn and young foals.
A severe case of carpal valgus
Category 1
Inadequate ossification
In the foetus, bones start off as cartilage
and later calcium is deposited within; this
process is known as ossification. One
group of ALD's are caused by inadequate
ossification of the small bones within the
knee or hock. If the uterine environment is
compromised in some way, e.g. infection,
parasitism, nutritional problems, this
ossification process can be interrupted
resulting in the foal being born with
weak, poorly developed bones. A similar
problem is seen in premature foals whose
skeleton has not had time to develop fully
whilst in the uterus. When the foal stands,
these complex joints can collapse
resulting in deviation of the limbs.
Category 2
Growth plate problems
A second group of ALD's are the result of
problems associated with the growth
plates of the long bones of the limbs.
These growth plates are at the ends of the
long bones and are a region of dividing
cells which ossify as they are produced.
The faster they divide and ossify, the faster
the increase in the length of the bone. If
the growth plate is dividing quicker on
one side than the other it will result in the
limb deviating towards the side that is
growing more slowly. Treatment is aimed
at either slowing down the faster growing
side or speeding up the slower growing
side. The majority of these types of ALD's
are seen at birth and it is not fully
understood why they occur. Nutritional
factors and positioning within the uterus
are just two of many factors which have
been implicated. ALD's can also occur in
the growing foal as a result of damage
to the growth plate, e.g. concussion
injury from hard ground.
Category 3
Flaccidity of joint
structures
A third group of ALD's can be seen
either alone or in conjunction with either
of the above two categories and they are
as a result of flaccidity in the ligaments
and other structures which hold the joints
together. These are often seen in
conjunction with flaccidity of the tendons,
resulting in foals whose fetlocks are down
on the ground. In most cases multiple
joints will be affected.
It is a condition where the leg deviates
either outwards (valgus) or inwards (varus)
from the midline when viewed from the front
or back. The joints most commonly affected
are the knees, fetlocks and hocks. The
majority of ALD's are encountered at birth
and are often associated with a problem
during pregnancy. There are a number of
different types of ALD's which have very
different treatment regimes.
