Arthritis

IT’S NOT JUST AN OLD DOG DISEASE!

TEXT: DR MEGAN ESTERHUYSEN (BVSC) ARTHRITIS

"Arthritis? No, it cannot possibly be! He is so young.”

These are the words of multiple clients holding their 7-month-old puppy or bringing their 2-year-old dog in for routine vaccinations. They are utterly shocked that their young dog is suffering from lifelong, progressive joint disease.

The shock these owners feel is largely because we have largely come to regard osteoarthritis as exclusively a disease of old age. Unfortunately, this is not the case. Whilst it is true that one in every five dogs suffers from osteoarthritis, and most of these are older, there are several orthopaedic conditions in young dogs that lead to very early onset arthritis.

The trick is to recognise these conditions quickly and get your vet involved. Early management can be lifesaving for these pets, so speak to your vet today if you have any concerns.

WHAT IS OSTEOARTHRITIS?

Osteoarthritis (OA), also known as degenerative joint disease, is characterised by the gradual breakdown of articular cartilage covering the surfaces of joints. The main functions of articular cartilage are to act as a shock absorber and decrease friction between the bones making up the joints. With osteoarthritis, catabolic processes lead to the breakdown of articular cartilage and the repair process can’t keep up with the rate of destruction and becomes limited. The overall result is that the cartilage cannot withstand normal load-bearing, and areas of soft cartilage develop cracks exposing the underlying bone.

IS MY PUPPY AT RISK?

Several conditions in young dogs can lead to osteoarthritis. Here we look at a few of these to help you detect them early on, before they result in irreversible damage.

ELBOW DYSPLASIA

Elbow dysplasia, defined as the abnormal development of the elbow joint, results in abnormal bone growth, cartilage development and joint stresses. The elbow joint in the dog consists of three bones: the humerus, radius, and ulna. If the bones do not fit together perfectly, there will be irregular weight distribution in specific joint areas.

Three conditions lead to elbow dysplasia:

• A fragmented medial coronoid process

• Osteochondrosis/osteochondritis dessicans of the medial humeral condyle

• Ununited anconeal process

Clinical signs often become apparent when your puppy is as young as 5-8 months of age. Signs to watch out for in these dogs include intermittent lameness on one or both front legs, stiffness, especially after sleeping and a stilted gait. The lameness is often worse after exercise or resting, so owners can think that the puppy simply overdid it or slept wrong.

Genetics also play a role, and predisposed breeds include Rottweilers, Labrador Retrievers, German Shepherds, Golden Retrievers and English Springer Spaniels.

However, elbow dysplasia is the most common reason for front limb lameness in dogs, so it should be considered in all breeds.

HIP DYSPLASIA

Hip dysplasia, on the other hand, refers to abnormal development of the hip joint. In this condition, the soft tissues which generally stabilise the joint become loose within the first few weeks of life. Therefore, the femur head (ball) is not well covered by the acetabulum (socket), causing the femur head to pop in and out of the acetabulum while the dog walks. As the dog ages, the hip dysplasia will result in hip osteoarthritis.

Clinical signs in young dogs can be seen as early as four months of age and again at 3-4 years of age. Puppies and young dogs with hip dysplasia are usually less active, which the owners often put down to having a quiet, well-behaved puppy. Other signs you may pick up include a reluctance to climb up or downstairs, or your puppy may have a bunny hopping gait where they bounce up the stairs with both the back legs. They tend to have under-developed muscles in their back legs and seemingly more muscled front legs.

Certain breeds are again predisposed due to genetics, including Great Danes, Saint Bernards, Labrador Retrievers, Germain Shepherds, Pugs, and Bulldogs.

CRANIAL CRUCIATE LIGAMENT RUPTURE

Another common orthopaedic disease we see in young dogs is cranial cruciate ligament rupture, and if left untreated, this condition will lead to osteoarthritis within the knee. The function of the cranial cruciate ligament is to stabilise the knee and prevent overextension and internal rotation of the joint. Rupture of the ligament is normally gradual with a progressive weakening or degeneration, almost like a fraying rope.

Clinical signs may be intermittent and include difficulty standing or jumping into the car, intermittent lameness and muscle wasting in the affected leg, as well as a decreased activity level. When the ligament completely ruptures, the dog will no longer want to bear any weight on the leg.

Certain dog breeds have a higher incidence of developing cranial cruciate ligament disease, including the Rottweiler, Labrador Retriever, American Cocker Spaniel, Chow Chow and English Bulldog.

MEDIAL PATELLA LUXATION

Lastly, we will look at medial patella luxation (MPL), a congenital/developmental disorder that can lead to osteoarthritis within the knee. The patella (kneecap) is a small bone that lies in the trochlear ridge (groove) of the femur and aids in extending the knee.

The kneecap lies within the powerful quadriceps muscle, and with MPL, the kneecap luxates (moves) to the inside of the joint. This, in turn, leads to malalignment of the quadriceps mechanism, which acts as a bowstring leading to the femur and tibia deforming into a pronounced outward bow.

Clinical signs may vary depending on the severity of the luxation and any concomitant skeletal deformities present. Grade 1 is when the patella (kneecap) can be luxated with manual pressure, and these pets generally do not show any clinical signs. With a Grade 2 luxation, the kneecap spontaneously luxates, and we typically see a “skipping” type of lameness.

The difference between Grade 3 and Grade 4 MPL is that with Grade 4 MPL, the knee cap is permanently luxated and unlike a Grade 3 MPL, the knee cap cannot be positioned back into the trochlear groove.

With a Grade 3 or 4 MPL, the lameness is more persistent, and an abnormal posture can be present. With Grade 1 and 2, lameness is intermittent, and the dog may occasionally lift the leg or stretch it back to allow the patella to pop back into the groove of the patella.

Medial patella luxation is common in our small breeds, with Poodles, Pomeranians, Yorkshire Terriers, Chihuahuas, French Bulldogs, Pugs and Bulldogs being some of the breeds which are predisposed to the development of this disease.

Dogs with MPL are predisposed to cranial cruciate rupture due to a change in the biomechanics within the knee joint. In fact, in one study, 41% of dogs suffering from cranial cruciate ligament rupture had concurrent MPL.

TAKE HOME MESSAGE

This is just a brief overview of some of the most common juvenile orthopaedic diseases which can lead to osteoarthritis in later life. So if you are at all worried about your beloved pooch, make an appointment with your local veterinarian today. By acting early, you could be changing the course of your dog's entire life. Don’t hesitate and act now!