What is the difference between primary and secondary osteoarthritis?

Primary osteoarthritis. Considered “wear and tear” osteoarthritis, this type of osteoarthritis is more commonly diagnosed. Here’s what experts know about primary osteoarthritis:

People tend to develop this type of osteoarthritis around age 55 or 60, says Yusuf Yazici, MD, a rheumatologist at New York University Hospital for Joint Diseases in New York.
It’s associated with aging — the longer you use the joints, the more likely you are to have this form of osteoarthritis.
Experts say that if we live long enough, we’ll all get this type of osteoarthritis to some extent, whether it’s very mild or more severe.

Secondary osteoarthritis. This type of osteoarthritis has a specific cause, such as an injury, an effect of obesity, genetics, inactivity, or other diseases. It tends to strike at an earlier age, around 45 or 50, Dr. Yazici says. Here are the risk factors that can lead to secondary osteoarthritis:

An injury: If you fracture a bone playing sports or in a car accident, you’re more likely to later develop osteoarthritis in that joint, and you’re more likely to experience osteoarthritis at a younger age than those who have primary osteoarthritis, Yazici says.
Obesity: “Obesity is a big factor,” Yazici says. Extra weight that bears down on the joints day in and day out can cause the joint to wear away faster. According to the Arthritis Foundation, every extra pound you gain adds three pounds of pressure to your knees and six pounds of pressure to your hips.
Inactivity. A sedentary lifestyle leads to weight gain, which can lead to osteoarthritis, Yazici says. Also, if you’re inactive, you have weaker muscles and tendons that surround the joint. Strong muscles help keep joints properly aligned and stable. Low-impact activities such as walking and swimming are important for keeping those muscles and tendons strong, he says.
Genetics. You may carry genes that put you at risk for osteoarthritis. In particular, experts have found that arthritis of the hands tends to have a genetic link among women. Osteoarthritis in the knee and hip also seems to run in families, Yazici says. “If your mother had it and your aunt had it, you’ll probably have it starting at about the same age,” he says.
Inflammation from other diseases. Diseases that cause inflammation, such as rheumatoid arthritis, can increase your risk of getting osteoarthritis later in life

Whether you have primary or secondary osteoarthritis, the treatment is the same. What’s most important, though, is to avoid the risk factors for secondary osteoarthritis that are within your control. “Stay active to keep muscles and tendons stronger, and lose weight or maintain a healthy weight,”