What’s best for arthritis: elliptical or treadmill?

DEAR DR. ROACH » If I have the beginnings of arthritis of the knee, is an elliptical machine better to use than a treadmill? — M.D.

DEAR READER » If you had an inflammatory arthritis like rheumatoid arthritis, there are medicines that can dramatically slow or stop progression of the disease. So I’m going to assume you have osteoarthritis, which is the most common arthritis of the knee.

Many people with severe osteoarthritis have such pain that exercise seems impossible. People write to me that they just can’t do any exercise, and indeed, it can get to the point where any movement is so painful that joint replacement becomes the only viable option. But for people with early arthritis, and even moderate arthritis, exercise is a powerful tool.

Elliptical machines put less impact pressure on the joint and will be better tolerated by people with more-advanced arthritis. Pools provide the most support for your joints. However, you can do whatever feels best to you.

DEAR DR. ROACH » In regard to your column on COVID-19 exposure, though it may seem logical to advise the person to avoid playing tennis that night with a contact of a COVID case, the person who was the contact was described as having “not seen his son for at least one week before the diagnosis.” In fact, the recommended look-back time for defining “contact” is 48 hours before the onset of symptoms or before a positive sample was collected in someone who is asymptomatic. According to the Centers for Disease Control and Prevention, a “close contact” is “someone who was within 6 feet of an infected person for a cumulative total of 15 minutes or more over a 24-hour period starting from 2 days before illness onset until the time the patient is isolated.”

Stating that the father of the son needs to quarantine would lead to more people quarantining than is currently recommended. Though that might truly be useful, current efforts are aimed at contacts of known cases whose exposure was within the period when the risk of transmission was most significant.

— M.K.

DEAR READER » I appreciate Dr. M.K., who is a professor of medicine and an infectious disease specialist, for writing. I wrote my answer to be cautious, but Dr. M.K.’s point is correct that the last exposure to the son was several days before the son developed symptoms — and presumably several days before the son had the positive test, though the question implied the test was earlier than the symptoms. The father would not currently be recommended to quarantine by the CDC’s guidelines.