All about ED
dysplasia (ED) is a general term used to identify inherited
polygenic diseases of the elbow in dogs. Affected
animals may exhibit intermittent lameness or an abnormal gait which is aggravated by exercise
or when the dog first moves following prolonged rest. Watch out for sudden or gradual front leg
lameness, morning stiffness or stiffness after a period of rest. In this technical article, vet
Peter van Dongen goes through the anatomy of ED.
Elbow Dysplasia (ED) is an abnormal development of the elbow joint and includes several primary
specific abnormalities affecting different sites in the joint. These abnormalities involve the
cartilage, which makes up the surface of the joint itself, or the other structures of the
joint, such as the bones themselves, the synovial membrane and the ligaments and tendons
surrounding the joint. The primary abnormalities cause secondary changes such as osteo-arthritis
(arthrosis, degenerative joint disease (DJD)) due to excessive wear and tear of the joint. Most
primary lesions occur in the young growing animal and are often present in both left and right
The Elbow Joint
elbow joint works like a hinge and allows movement mainly in one plane only. It is made up
of three bones, which normally fit together perfectly (See photo and line drawings).
The single bone of
the upper foreleg is called the humerus, the two bones of the lower foreleg are called the
radius and the ulna. The ulna is the longer one, which makes up the point of the elbow,
called the olecranon. The distal (furthest away from the body) part of the humerus is
called the condyle, which has a medial (towards to inside of the body) and lateral (towards
the outside) part. The proximal (closest to the body) part of the ulna has a medial and
lateral coronoid process and an anconeal process, in between which the trochlear notch
articulates with the humerus. The proximal part of the radius is called the radial head.
The ends of the bones are all covered by hyaline cartilage (joint cartilage) which is
normally very smooth. The joint is surrounded by a synovial sac, called the joint capsule,
which contains the synovial fluid (joint fluid) to help lubricate the joint. The bones are
held together by means of ligaments (collateral ligaments), one on either side of the
joint. In addition several tendons cross the joint on either side.
If there is any
change to the anatomical build of any part of the above, the joint will not fit together
properly, leading to damage to one or more of the structures involved and an excessive wear
and tear of the joint. The elbow joint is particularly prone to these changes as it is the
major point of movement of the foreleg. The other joints of the foreleg, shoulder and
carpus (wrist) do not move as much during the normal locomotion of the dog.
Causes of Elbow Dysplasia
Elbow dysplasia is a multi-factorial disease, which means that there are several factors
which can influence the occurrence of the condition. The genetic make-up of the dog is by
far the most important factor. Furthermore there are many factors which influence the
chance of developing ED or the severity of the problem, such as nutrition, hormonal status,
growth rate and exercise level. The latter factors can not cause or prevent the disease on
their own and they can not influence the way that the disease is passed on to a dog’s
mentioned above, the most important factor in the development of ED is the genetic make-up of a
dog. Unfortunately the disease is controlled by a number of genes (it is ‘polygenic’) and this
makes for a complicated inheritance. It also means that certain breeds of dog are more prone to
the development of ED than others, as many dogs within one particular breed have a large number
of genes in common. In general, these are the medium-to-large and giant breeds.
The breeds which are prone
to any particular primary condition are mentioned below. Males are affected more often than
females, possibly due to their faster rate of growth or heavier build. One of the problems in
deciding which dogs to breed from is the fact that many dogs which are affected genetically, or
even anatomically, are not necessarily affected clinically. They may not show any clinical
symptoms such as lameness. These dogs are called sub-clinical dogs. They can only be detected
radiographically at the moment. In the future perhaps there will be DNA tests available to
assess the genetic make up of a dog for a particular trait.
Osteo-Chondritis Dissecans (OCD)
This condition affects the distal aspect of the medial part of the humeral condyle, where
it articulates with the ulna. It causes thickening of part of the articular (joint)
cartilage, which is then prone to fibrillation, fissuring and separation. If a flap
forms, this can become detached and ‘float’ inside the joint (‘joint mouse’) which leads
to intra-articular inflammation. Sometimes the thickened cartilage can be seen as a
‘defect’ in the bone contour on radiographs (x-ray films) on some views, but usually this
condition is not actually seen itself on radiographs, only the secondary changes which
result from the condition. When a loose flap is formed this can sometimes become
mineralised, in which case it can be seen.
- Fragmented (or
un-united) Coronoid Process (FCP)
This condition affects the proximal aspect of the ulna on the medial side. It leads
to a fragmentation and/or fracturing of the coronoid process, where the ulna articulates
with the humerus. This in turn leads to joint inflammation and secondary changes as
above. The primary lesion is very rarely seen on radiographs, even on good quality
radiographs. This is the most common primary condition causing elbow dysplasia.
Anconeal Process (UAP)
This condition affects the proximal aspect of the ulna at the top of the trochlear
notch. The anconeal process sometimes has a separate centre of ossification, which means
it develops separately as part of the boney ulna from cartilage and joins the shaft of
the ulna later. Between the anconeal process and the shaft of the ulna lies a growth
plate (physis), made up of cartilage, which contributes in part to the growth in length
of the ulna. When the anconeal process does not join the rest of the ulna, we call this a
UAP. In about 40% of cases it affects both left and right elbow.
Medial Humeral Epicondyle
This, much more rare, condition affects a part of the distal humerus, just proximal
to the medial aspect of the humeral condyle. Again, this part of the bone has a separate
centre of ossification and sometimes fails to joint the rest of the humerus. It generally
causes a milder form of lameness than the other primary lesions.
- Short Radius
This is a condition where the radius has not grown at the same rate as the ulna,
leading to an incongruency of the elbow joint, called a subluxation. It is usually caused
by a premature closure of one of the growth plates (physes) of the radius. It is quite
rare, and often thought to be the result of trauma to the growth plate.
- Short Ulna
This is a condition where the ulna has not grown at the same rate as the radius due
to premature closure of the distal ulna growth plate. It leads to a similar elbow
subluxation as short radius syndrome.
Dislocation of the Elbow
There are two forms of this condition, where the elbow joint has not been formed
properly from birth. It leads to a malformation of the joint, again leading to joint
incongruency and subsequent arthrosis. In one form of there is lateral (outwards)
rotation of the ulna. In the second form of Congenital Dislocation of the Elbow
there is caudo-lateral (backwards and outwards) luxation of the radial head.
Breeds Most Prone to ED
OCD: Labrador Retriever, the Golden Retriever and the Rottweiler.
Symptoms usually develop between 4-5 months of age.
FCP: Labrador Retriever, the Golden Retriever, the Rottweiler, the
German Shepherd Dog and The Bernese Mountain Dog. Other breeds affected are the St.
Bernards, Chows, Rhodesian Ridgebacks and Newfoundlands. Symptoms usually develop between
4-5 months of age. Sometimes FCP and OCD occur in the same joint at the same time.
German Shepherd Dog and the Bassett Hound. More rarely we see it in Wolfhounds, Rottweilers,
St. Bernards and Great Danes. Symptoms usually develop between 4-5 months of age.
Un-united Medial Humeral Epicondyle:
Labrador Retrievers are prone to this condition.
Short Ulna Syndrome: Great Danes, Irish Wolfhounds and the Bassett
Hound or after trauma.
Congenital Dislocation of the Elbow - (lateral (outwards) rotation of the
ulna. This is mostly seen in Shelties, Pekingese, Cocker Spaniels, Yorkshire Terriers,
Boston Terriers, Miniature Poodles, Pugs, Chihuahuas and Miniature Pinschers. It is usually
recognised within the first three months of life.
Congenital Dislocation of the Elbow (caudo-lateral (backwards and
outwards) luxation of the radial head. This is mostly seen in Pekingese, Yorkshire
Terriers, Pomeranians, Staffordshire Terriers, Boxers, Bulldogs, Bull Mastiffs, Old English
Sheepdogs and Rough Collies. Affected animals are often 4-5 months old at presentation.
This term is often used inconsistently or confusingly for one or several of the
conditions above. Osteochondrosis is a developmental orthopaedic condition in which a
disturbance in the normal process of endochondral ossification results in a thickening or
retention of articular or physeal cartilage. The thickened cartilage is then prone to
fibrillation, fissuring and separation. If a cartilage flap develops in articular cartilage,
intra-articular inflammation and degenerative joint disease may result and the condition is
then most appropriately described as osteochondritis dissecans (OCD).
is one of the two processes in which bones are formed. In this case bone develops on a
preformed cartilagenous matrix, either at the end of the bone or in the physis. It is the main
process behind the growth in length of the long bones in the body.
ossification is the second process in which bones are formed. In this case bone forms in bands
of connective tissue. This happens in flat bones, such as the skull bones and the pelvis, and
it is also the way in which bones grow in width. The primary conditions 1-6 are all thought to
be due to osteochondrosis.
symptoms of elbow dysplasia are dependent on the particular condition present in the patient
and the chronicity of the problem. Generally it causes lameness, although this can be very
subtle and easily missed by an owner, particularly as the problem often occurs in both legs at
the same time. In such cases it often causes a minimal stiffness rather than a true lameness.
It can also cause pain, especially on manipulation, such as extension, flexion and rotation
on the joint. The lameness is often a ‘starting lameness’, which gets better as the patient
‘warms up’ and sometimes intermittent in nature. This is similar to the type of lameness seen
in older patients with degenerative joint disease. The most reliable way to make a
diagnosis is radiography (x-raying).
Radiography is used to detect either the primary lesion itself or the subsequent degenerative
joint disease. Normally three different views are taken of each joint to fully assess the joint
structures, two in a lateral plane (with the x-ray beam directed sideways through the joint,
whilst extended and flexed) and one in the cranio-caudal plane (beam directed from the front of
the joint to the back of the joint). Different areas of the joint are more clearly identifiable
on each view. As already mentioned above, not always is it possible to identify the primary
condition present in the joint, but it is usually possible to detect the secondary changes.
Together with the clinical symptoms, the age of the patient and more importantly the breed, it
is often possible to come to a definite diagnosis.
Prevention of Elbow Dysplasia is based on sensible breeding, using only dogs not affected or
only very mildly affected by the condition. To this purpose it is necessary to radiograph each
and every dog, as there are many dogs with radiographic evidence of elbow dysplasia, but
without any clinical signs. These ‘sub-clinical’ cases would be missed if they were not
radiographed. Only dogs who have no, or only very minor, radiographic evidence of elbow
dysplasia should be used for breeding. In the UK the ED scheme has been operational for the
last few years to this purpose. This scheme is run by the British Veterinary Association and
the Kennel Club together, according to guidelines by the International Elbow Working Group.
Dogs examined under the
scheme are radiographed as described above, at an age of at least one year old, and the
radiographs are then sent for examination by a select group of scrutinisers who have extensive
experience in the assessment of radiographs. A grade for each elbow of each patient is decided
upon, based on the presence or absence of primary lesions, as well as the presence or absence
of any secondary changes in the joint. The score for each elbow can be: 0 if the joint is
normal, 1 when there is mild ED, 2 if there is moderate ED or any primary lesion, and 3 if
there is severe ED. The overall grade for each individual patient is the highest of the two
scores, not the total, as in the hip scoring system. Only dogs with scores of 0 or 1 should be
used for breeding purposes. The results of any dog radiographed under the ED scheme are kept on
record by the Kennel Club. The effect of this system will only really be seen after several
generations of selective breeding in the affected breeds.
of ED depends on many factors, such as the nature and severity of the primary problem.
Conservative treatment, such as weight control and exercise control, are important in each and
every case. In a number of cases, drugs, used to reduce pain or inflammation, are needed.
Furthermore, in some cases surgical intervention is necessary. In some cases nutritional
supplements are useful to reduce the possible future build up of arthritic changes. Other forms
of treatment include physiotherapy, homeopathy and acupuncture. Nearly all dogs can be managed
successfully, if the symptoms are recognised and the dog is diagnosed early on in the disease
Peter van Dongen
qualified as a vet at the Utrecht Veterinary school, The Netherlands, in March
1990. He worked in a mixed practice in Louth, Lincolnshire, UK, for 3 years, before moving to
Borough Green, Kent, UK. At the same time he limited himself to small animals only. Since
December 1996 he has run his own branch practice in Allington, Maidstone, UK.
In May 1995 Peter started agility (after years of just thinking about it!) with
his Jack Russell Cross 'Basil' (a bitch!), then 5 years old. Since then they have qualified for
many finals, including 'Crufts' and 'Olympia'. Basil won the coveted Crufts 2001 title in the
individual mini agility.
Peter passed the British Agility Club Instructors' exam in October 1999 and has
since done the British Agility Club Judging Workshop.
Peter regularly writes for various agility magazines and web sites and has been
the official British Team Vet for the Agility World Championships for the last three years.
Peter and his wife Carry still live in Borough Green with their two dogs and two
cats. His little Jack Russell X, Sky, has just started agility training and will hopefully
follow in Basil’s footsteps!