But I Didn’t Injure It?

by Symptom Advice on October 21, 2011

Knee pain is a common problem, accounting for a significant number of office visits to PCPs each year. While it is common to have an associated injury that triggered the knee pain, in some cases joint pain, specifically knee pain, can present with no obvious cause. There are many possibilities for why a patient might experience knee pain in the absence of trauma and like many situations in medicine, the history provided by the patient often offers the key to diagnosis.

Perhaps the most widely publicized cause of traumatic knee pain is Lyme disease. this tick-borne infection can indeed lead to joint aches, also termed arthralgias. While smoldering knee pain can be associated with lyme, specifically chronic Lyme, it’s not uncommon for the presentation to be more dramatic. Sudden swelling and redness of a knee, often with associated pain and even fevers, may bring the patient to the physician’s office for evaluation.

There are other infections that can strike the knee joint. other tick-transmitted infections may attack the joint, however these are quite rare (but on the rise). Not as rare are bacterial infections of the knee joint or even the bones that constitute the knee’s foundation. Staph infections can enter the joint, typically via a break in the skin, and can be quite painful. Syphilis, a sexually transmitted disease that is NOT extinct, can lead to knee pain in the absence of trauma. in fact, so can untreated gonorrhea, a separate STD.

Mechanical problems within the knee can lead to pain, even if there was no injury that was the clear source of pain. A somewhat disorganized flap of tissue known as a plica can yield pain, as can occult tears of the meniscus. likewise, tears to the knee’s cartridge “caps” are rare in the absence of a mechanism of injury, but can occur.

It is possible to have knee pain due to underlying crystal disease. The most common condition, gout, leads to deposition of microscopic crystals in the knee’s fluid, which generate pain and redness. The knee is an uncommon location for gout attacks, but I’ve seen it. another condition called psudogout acts the same way, but by precipitating a different type of crystal in the knee.

One of the more common causes of knee pain is arthritis. There are many different kinds of arthritis, the most common of which is osteoarthritis, or degeneration of the knee joint’s cartilage which leads to narrowing of the joint space and pain. other forms of arthritis exist, however, and autoimmune arthritis is one of them.

Autoimmune conditions are ones where the body inappropriately produces antibodies (proteins that “attack” tissue) against its own components. in the case of rheumatoid arthritis, for example, these proteins lead to an inflammatory cascade that causes pain and joint damage. many other autoimmune diseases exist.

Diagnosing knee pain without a clear cause often requires testing, sometime extensive testing. If you fall into this category and don’t know why your knee aches, the smartest move is to see your PCP. They can rule out dangerous conditions, treat your symptoms and keep you on your feet.

Dr. Brian Irwin is a family physician at Tamworth Family Medicine, a division of Huggins Hospital.

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