Of course you know the reason for those aches and joint pains. Lupus is synonymous with joint pain, right? But despite rest for a week, the pain only gets worse and you start limping. After a while you rarely walk at all to give your hips a chance to recover from a few ‘bad days!’ But alas, a good week later and your joints still hurt. Throwing your hands up in the air, you head to the doctor.
The doctor does a good physical exam and finds nothing abnormal and x-rays show nothing abnormal, too. But, the MRI of your hip isn’t so normal. It shows that you’ve developed a condition called osteonecrosis or avascular necrosis in both your hips which is causing your pain.
What could have been the cause of that long ‘o’ word, and more important, what is osteonecrosis? There are a lot of causes of osteonecrosis; pancreatitis, sickle cell anemia, lupus blood clots and injury. Divers can develop osteonecrosis if they develop ‘the bends;’ the formation of nitrogen clots in the blood.
Basically, anything that obstructs blood flow to the bone is a potential cause of
osteonecrosis (ON). Why might that be? Just because bone doesn’t move, it doesn’t mean that bone is dead. It is very much alive and fed, nourished by frequent blood supply.
If that blood supply is cut off, needed oxygen and nutrients can’t get to the bone; deprived of these, bone dies. Death generally occurs at the end of long bones; so osteonecrosis may involve the hips, the knees, the shoulder, the ankle: most often the weight-bearing joints. However, it is definitely not unheard of in upper body joints.
We’ve talked about some causes of osteonecrosis, but are there others? Yes, yes and yes.
Lupus and other autoimmune diseases are often treated with corticosteroids because of their immediate anti-inflammatory effects. However, it’s thought that corticosteroids can cause osteonecrosis, when used at high doses or chronically. How? There is a theory, unproven, that corticosteroids interfere with fat metabolism and that subsequently reduce blood flow to the bones resulting in bones death.
Usually, when a medication has side effects, withdrawal of that medication is enough to stop the side effects. This isn’t so with corticosteroids which are the suspected cause of @35% of osteonecrosis cases.
When circulation of blood to the bone is compromised and bones die, gas, fluid and other necrotic debris inside bone cannot be removed by normal circulation; pressure builds inside the bone, causing pain. This pressure from gas and other necrotic debris keeps accumulating and pain escalates. That is why rest didn’t help.
Because of the increase in the pressure and degeneration of bone, osteonecrosis is a very painful condition. Often because of the pain, the patient doesn’t exercise and gains weight as a result. That extra weight adds unnecessarily to the pressure on the joint, only increasing the pain.
So, lupus can cause osteonecrosis by causing blood clots which compromise blood flow; also medication used to treat lupus and other autoimmune diseases can cause osteonecrosis by decreasing blood flow to bones resulting in bone death. Also, trauma, like a fracture can cause osteonecrosis by clotting blood at the fracture site.
In another post, we’ll discuss treatment options; suffice it to say, they are limited. Unfortunately, research dollars are limited, too, because osteonecrosis is amongh those ‘but you don’t look sick’ conditions. However, there is research being done which we will discuss.
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