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Hip Dysplasia is a terrible genetic disease because of the
various degrees of arthritis (also called degenerative joint
disease, arthrosis, osteoarthrosis) it can eventually produce,
leading to pain and debilitation.
The very first step in the development of arthritis is articular
cartilage (the type of cartilage lining the joint) damage due to
the inherited bad biomechanics of an abnormally developed hip
joint. Traumatic articular fracture through the joint surface is
another way cartilage is damaged. With cartilage damage, lots of
degradative enzymes are released into the joint. These enzymes
degrade and decrease the synthesis of important constituent
molecules that form hyaline cartilage called proteoglycans. This
causes the cartilage to lose its thickness and elasticity, which
are important in absorbing mechanical loads placed across the
joint during movement. Eventually, more debris and enzymes spill
into the joint fluid and destroy molecules called
glycosaminoglycan and hyaluronate which are important precursors
that form the cartilage proteoglycans. The joint's lubrication
and ability to block inflammatory cells are lost and the debris-tainted
joint fluid loses its ability to properly nourish the cartilage
through impairment of nutrient-waste exchange across the joint
cartilage cells. The damage then spreads to the synovial
membrane lining the joint capsule and more degradative enzymes
and inflammatory cells stream into the joint. Full thickness
loss of cartilage allows the synovial fluid to contact nerve
endings in the subchondral bone, resulting in pain. In an
attempt to stabilize the joint to decrease the pain, the animal's
body produces new bone at the edges of the joint surface, joint
capsule, ligament and muscle attachments (bone spurs). The joint
capsule also eventually thickens and the joint's range of motion
decreases.
No one can predict when or even if a dysplastic dog will start
showing clinical signs of lameness due to pain. There are
multiple environmental factors such as caloric intake, level of
exercise, and weather that can affect the severity of clinical
signs and phenotypic expression (radiographic changes). There is
no rhyme or reason to the severity of radiographic changes
correlated with the clinical findings. There are a number of
dysplastic dogs with severe arthritis that run, jump, and play
as if nothing is wrong and some dogs with barely any arthritic
radiographic changes that are severely lame.
www.offa.org/hipgeninfo.html |
