Christopher Evans, DSc, PhD, of the Maurice Mueller Professor of Orthopaedic Surgery at Harvard Medical School in Boston, says, ‘Everybody says that arthritis is one word, but the conditions are quite different.’ So how do you tell the two apart? Firstly, OA tends to occur in older people, but RA can come on quickly at any age, even in children. Evans explains ‘unless you’ve been banged up on a sports field or in a car crash, it’s very unusual to see someone with osteoarthritis at a young age.’
Also, what actually happens to your wellbeing in each disease is different. In OA, your cartilage in your joints slowly wear away so that your bones rub against each other, whilst in RA your immune cells attack your joint’s lining, the synovium, because they think they see an invader. In RA, your cell-signalling molecules pour into your blood stream, which can cause RA-specific symptoms such as fever and swelling, and the inflammation it causes can result in heart, lung, and eye damage.
When it comes to the specific joints that are affected, in OA the worst damage tends to occur in larger weight-bearing joints, such as a hip or a knee. RA, on the other hand, tends to affect both sides of the body, attacking smaller joints first until they are painfully red, warm, and swollen. Evan says, ‘Rheumatoid arthritis can spread from one hand to the other and then throughout the body to as many as 30 different joints, whereas osteoarthritis affects a very limited number of joints.’
Finally, both conditions require treatment with steroid injections into the joint, and oral NSAID drugs like ibuprofen and naproxen to fight pain, but people RA need stronger oral steroids, like prednisone, which can cause bone thinning, and joint destruction-preventing drugs. Also, joint deformities are more common in RA, whilst OA patients are more likely to experience painful bony lumps or spurs in their fingers, shoulders, elbows, hips, knees, or ankles. Both conditions may require joint replacement surgery.