Arthritis is not the only possible cause of knee pain, swelling, and disability.
Does your knee hurt? Your first thought might be that it's arthritis, and you would have a good chance of being right. The most common form of the disease, osteoarthritis, is caused by wear and tear of the knee cartilage and affects some 27 million Americans. But pain and other knee symptoms can be caused by to other things—some you don't need to worry about too much, but there are others that will need attention.
Most knee problems trace back to injury, overuse, or a developing joint condition. To understand the many and varied causes of knee pain and what you can do about them, we spoke to Dr. Robert Shmerling, associate physician and clinical chief of rheumatology at Harvard-affiliated Beth Israel Deaconess Medical Center. Here are some common types of problems and what you should do to follow up.
A common injury that causes knee pain is a torn meniscus—the dense cap of cartilage at the top of the tibia (shin bone) that absorbs the shock of the femur (thighbone) bearing down on it. Twisting the knee suddenly while bearing weight can tear the meniscus, or it may tear from age-related changes.
Hearing a sudden pop or cracking sound points strongly to a physical injury; so does a knee that locks up or suddenly gives way when you walk or stand. "This may be something that could be repaired with surgery," Dr. Shmerling says.
Pushing the knee past its physical limits can stress the tendons associated with the knee. This causes pain and inflammation (tendinitis) and difficulties with normal activities. Tendons are tough bands of tissue that anchor the tips of muscles to bones and allow joints to move.
Weekend warriors who play or work too hard, especially after inactivity, may get tendinitis. For runners, tennis players, cyclists, and skiers, the trouble spot is often the patellar tendon, which connects the kneecap to the shinbone. The treatment is basic self-care, such as anti-inflammatory pain relievers, rest, and ice. In severe or persistent cases, you might be offered a corticosteroid injection.
Occasionally hearing crunching or crackling sounds as you flex the knee does not necessarily indicate a problem. But if you hear sounds and also feel pain while climbing or descending stairs, you might have chondromalacia patella—a condition related to irritation or breakdown of the cartilage on the back surface of the kneecap that allows it to slide smoothly and painlessly across the knobby end of the femur.
You may feel discomfort when you kneel or squat, or when you sit with your knees bent for extended periods. Unless the pain is intense and persistent, you may not need to do anything about it besides just resting and applying ice packs.
Other types of arthritis
Osteoarthritis is just the most common form of arthritis. Although rheumatoid arthritis is much more common among women, men get rheumatoid arthritis, too. The typical symptoms of this would be pain and swelling in the hands, wrists, and other joints (which may include the knee) that is worse in the morning.
The knee is also a favorite spot for a little-known arthritic condition called pseudogout. The name reflects the fact that its symptoms can resemble gout, in which crystals of uric acid build up in the joint. In pseudogout, the material that builds up is calcium.
Pseudogout becomes more common with age. Typical signs are swelling, pain, stiffness, and a feeling of heat or tender-ness. Flare-ups of pseudogout can last up to a few weeks. Anti-inflammatory pain relievers or corticosteroids can help you ride out the attacks.
When to see a doctor
If your knee hurts a lot and for an extended time, and if it prevents you from functioning day to day, those are good reasons to see your primary care doctor. If a significant knee injury is suspected, the doctor may send you for an MRI scan to confirm it. The next stop could be an orthopedic surgeon.
If the problem is severe or persistent, you might end up seeing a rheumatologist—an expert in joint diseases. You'll get education on the condition and practical advice on what combination of medication, self-care, and physical therapy will relieve symptoms and get you back into action.