Originally Answered: What is the difference between arthritis, hip dysplasia, and old age in dogs?
Hip Dysplasia is the result of improper joint formation at birth, In short, "the ball doesn't fit in the socket". this could mean the socket is too large, or doesn't have the appropriate depth or shape to maintain proper control while allowing smooth and unrestricted movement. This also causes the ligiments and muscles to form improperly, and are generally not strong enough to support the leg.
If it isn't treated at a young age, it generally results in arthritis.
Arthritis (in it's common form) is the collective effects of the degeneration of various parts of the joint. The cartilage breaks down, leaving less padding for the joint, and the natural lubrication of the joint is decreasing. This causes inflammation in the joint, resulting in arthritis pain.
At his age and size, it would be very possible that the stiffness is a result of arthritis. If it were hip dysplasia, i would suspect you would have seen more severe symptoms well before now. What is described as "old age" is generally arthritis.
Arthritis pain is easily controlled, as well as supporting the joint tissue.
Supplements like a glucosamine/chondroitin mix will enhance the lubrication of the joint, preventing extensive cartilage wear. There are several minerals that are required in order for the body to use glucosamine, which is why I would insist you use a specially formulated supplement like Cosequin, Dasaquin, or Glycoflex.
The inflammation is controllable with anti-inflammatories - "doggy advil". Rimadyl, Deramaxx, and Previcox are most common, and can be paired with Tramadol for extended relief.
Personally, I use Glycoflex on my dog, and have seen a huge difference in her motility and attitude in general. I do use Previcox on an as-needed basis, although I have had dogs in the past that required daily anti-inflammatories.
And I'll keep going... (phew - one long subject!)
Some dogs respond better to some medications than others. Just like I prefer Ibuprofen, you may prefer Tylonol. If you try say, Rimadyl and don't see the result you're looking for, try another before giving up.
I do want to encourage you to try a joint supplement, no matter how you decide to treat. You can prolong your dog's joint health and increase his quality of life without using a drug. The anti-inflammatory will only create comfort, while the supplement will support joint health.
Correct and Functional muscle is going to do alot for your dog, since that is what allows movement of the joint to begin with. Light, physical activity can promote overall health. Any extra weight needs to be lost with diet and light excercise - there is careful balance between keeping the muscles in shape and straining the joint. Swimming (or wading) is wonderful for circulation and muscle maintainance. Light walks (the softer the surface, the better) are also great.
Lastly, it could absolutely be something else. Cruciate tears, spinal damage, Lyme disease are all possibilities, although much less likely. A veterinarian could tell you much, much more.