John, a 67-year-old man who loved to work in his garden, was having trouble with his hands. He was experiencing pain, slight swelling, and a few bumps on the first two joints of his fingers, along with about 30 minutes of morning stiffness. Initial diagnosis showed a normal erythrocyte sedimentation rate (ESR or sed rate) and the slightly positive rheumatoid factor. Does John have osteoarthritis or rheumatoid arthritis? Let’s take a closer look.

Osteoarthritis is often referred to as degenerative joint disease. When cartilage wears away, the unprotected bones rub together, causing severe pain and reducing joint movement. As the bone tries to repair itself, hard bony knobs on the end or middle joints of the fingers or other joints can form. Even though cartilage breakdown may cause some inflammation, generally, inflammation and osteoarthritis do not go hand in hand.

Rheumatoid arthritis, on the other hand, is an inflammatory arthritis. It is caused when the immune system goes astray, mistaking joint tissue for a foreign invader. The result is inflammation with red, hot, tender, and swollen joints. Joints commonly affected by osteoarthritis are weight-bearing ones such as the knees and hips, as well as the neck, lower back, thumb base and first and middle finger joints.

However, rheumatoid arthritis tends to target the middle finger joints, knuckles, wrists, elbows, knees, ankles, feet, and neck. It usually affects joints symmetrically (both sides), involves many joints, both large and small, both weight-bearing and not. Morning stiffness, due to fluid accumulation around the joints when they are rested, is an indicator of inflammation. In active cases of rheumatoid arthritis, morning stiffness tends to last at least one hour. In osteoarthritis, stiffness is brief and fades quickly with movement.

The rheumatoid factor, an antibody, can be detected in the blood of about 70-80 percent of rheumatoid arthritis cases, thus called “RF-positive RA.” Generally speaking, the higher the rheumatoid factor, the more severe the arthritis. Measuring rheumatoid factor is extremely useful, but it can be misleading. Up to 20 percent of rheumatoid cases have a negative factor, called “RF-negative RA.” It also can be present with other diseases without arthritis and becomes more elevated with age. In essence, having a positive rheumatoid factor does not necessarily mean you have rheumatoid arthritis, nor does having a negative factor mean you do not. If a physician is still in doubt about what type of arthritis a patient has, further tests such as the ESR, can reveal the degree of inflammation. In general, people with osteoarthritis have normal ESR or mildly elevated ESR.

The accurate diagnosis of arthritis depends on a detailed medical history, physical examination and laboratory results. In John’s case, the verdict was osteoarthritis, even his rheumatoid factor was slightly positive.