If your knee swells and you haven’t injured it, what could be going on?   Well, most of the time you probably didn’t even realize that you twisted it just a tiny bit, perhaps when stepping off that curb late last night. Usually, there is some prior wear and tear arthritis. Yes, one of the many joys of middle age is that the knees take the brunt of all those years of sports and of course the ever expanding waistline.

But not all knee swelling is from wear and tear arthritis or acute injury. Let’s look at some other diseases which can affect the knee.

Gout can affect not only the big toe but also other joints. This includes the knee. Attacks can be precipitated by wine, red meat and other foods. The knee swells, is red and painful. If your doctor decides to take some fluid out of your knee to help reduce the pain and swelling, he or she can have the fluid checked for a certain type of crystals seen only in gout.

Pseudogout (who thought of these names anyway?) like gout forms crystals but a different type. It can diagnosed as well by viewing the crystals in the joint fluid. At times excessive calcium deposit in and around the joint can be seen.

Lupus is an autoimmune disease, which means the body mistakenly fights itself. It can affect many joints, including the knee. The knee swells, is red and painful. Often, the patient feels weaker than normal when the disease flares.

Other autoimmune disease such as rheumatoid arthritis can cause knee swelling. However, rheumatoid  arthritis usually affects both knees rather than just one.

Infections, especially gonorrhea can affect the knees. A rash is also seen in other areas of the body.

Occasionally, some unlucky patient may have both wear and tear arthritis and one of the above diseases. This makes it difficult to sort out. Just remember to always tell your doctor what other medical conditions you have, because one of these just might be the cause of that painful knee.