there are air bubbles rising to the top inside my knee. wait, what?
October 20, 2008 10:35 AM   Subscribe

there are air bubbles rising to the top inside my knee. wait, what?

for the past three days I have had the distinct impression that there are air bubbles rising to the top inside my knee. you know how it looks when air bubbles rise to the top in a bathtub or cooking pot? it feels just like that. they rise usually three at a time, sometimes five, and continue with few interruptions for minutes. this is not painful but it's the strangest sensation I have experienced to date. it's as if you are being tickled from inside.

this is occurring on the inside top of my left knee. judging from this wikipedia diagram we're talking about the femur region of the knee.

I have previously had an MRI, xray and physical examinations over a mysterious painful sensation in my knee. climbing stairs was painful and bending the knee past a certain point produced a distinct popping sound. the latter still happens but I am currently pain-free. (I'm a runner and running does not seem to be a problem at all since I am not bending the knee far enough to encounter this problem during sessions.) no obvious damage has ever been diagnosed but I avoid squats these days and feel somewhat more fragile than I used to.

so, hivemind. I am stumped as to what might be the case and quite frankly I'm weary of yet another trip to a GP that ends up in nothing because they can't find what's wrong. any thoughts on what could be the issue with my knee or what kind of attention I should ask for?
posted by krautland to Health & Fitness (9 answers total) 2 users marked this as a favorite
Perhaps you shouldn't see a GP, but an orthopedic doctor, instead, who specializes in knee joint issues.
posted by Blazecock Pileon at 10:48 AM on October 20, 2008

The popping and pain sound a lot like what I've been experiencing. For me, the pain would come and go, so I experienced months at a time that were pain free, but the popping never stopped. I was diagnosed with runner's knee, told to ice it and do some exercises, and both the popping and pain have lessened a great deal.
posted by amandarose at 10:51 AM on October 20, 2008

posted by amro at 11:25 AM on October 20, 2008

You have somehow altered the mechanics of how your kneecap slides through the patellofemoral groove, which is resulting in crepitus.

Pain descending stairs and bending the knee past a certain point, and/or hearing a popping/clicking sound are pretty common symptoms for someone with patello-femoral syndrome. (of course go see an orthopaedist about this, again)

This condition is commonly caused by a weakness in vastus medialis, but can have a number of other causes, so you want to have a trained physical therapist rehab you.

As vastus medialis is involved in terminal knee extension, an excellent way to exercise it is to walk up stairs backwards.
posted by zentrification at 11:36 AM on October 20, 2008

amandarose, check your Mefi Mail!
posted by amro at 12:08 PM on October 20, 2008

Response by poster: yikes, Crepitus sounds like a hit for my symptoms.

zentrification: do you think running can make this worse?
posted by krautland at 12:17 PM on October 20, 2008

The most accepted explanation for the popping noise in your knuckles you get when you pull your fingers is cavitation:

When a manipulation is performed, the applied force separates the articular surfaces of a fully encapsulated synovial joint, which in turn creates a reduction in pressure within the joint cavity. In this low pressure environment, some of the gases that are dissolved in the synovial fluid (which are naturally found in all bodily fluids) leave the solution creating a bubble or cavity, which rapidly collapses upon itself, resulting in a "clicking" sound. This process is known as cavitation. The contents of the resultant gas bubble are thought to be mainly nitrogen.[4] The effects of this process will remain for a period of time known as the "refractory period", which can range from a few minutes to some hours while it is slowly reabsorbed back into the synovial fluid. There is some evidence that ligament laxity may be associated with an increased tendency to cavitate.[5]

While you may indeed have crepitus, I think the sensation you are having of bubbles rising in your knee is just that. Bubbles generated by the cavitation process, according to this passage, can hang around for as much as hours, and I think those persistent bubbles are rising in your knee and you are feeling them do so.

Note the final sentence of the excerpt: "There is some evidence that ligament laxity may be associated with an increased tendency to cavitate."

If you do have such laxity in your ligaments, that could account for the problems you have when you bend your knee too far, and the fact that no damage is showing up on an MRI.

In one of your previous questions you mention that you've had some problems with near-fainting, and someone suggested you could be suffering from orthostatic hypotension. OH is associated with Marfans and other collagen disorders in which collagen is too elastic and also has a tendency to get stretched out beyond its elastic limits. This could explain any laxity of the ligaments of your left knee.

By the way, there is an interesting tension in claiming the collapse of bubbles generates the sound of cracking joints, and also that the bubbles can hang around for hours. It would be nice to see a discussion ruling out the possibility that the bubble coming into existence is the source of the sound.
posted by jamjam at 1:20 PM on October 20, 2008

Krautland, you've altered the mechanics of your knee somehow, so potentially doing any consistent exercise on it could worsen your condition.

That said, as you don't have pain while running, you may not be doing any damage.

If you stop running now and start working on rehabbing the cause of the problem, you'll recover much quicker.

I disagree with jamjam on the orthostatic hypotension, first crepitus isn't caused by ligament laxity as no ligaments hold the kneecap in place. It's held in place by the quadricpes and patellar tendon. Second collagen disorders are very rare compared to the incidence of patella dyfunction in the general population, unless you have significant reason to believe otherwise follow occams razor.

Patello-femoral dysfunction is a very common condition, particularly among women, any qualified sports orthopaedist should have no problem diagnosing you and sending you to an appropriate physical therapist.
posted by zentrification at 1:38 PM on October 20, 2008

This is classic TMS. No trauma? Football injury?

There is nothing wrong with you. Seriously.

Tension Myositis Syndrome

Seeing doctors and getting MRI's, tests, etc.. will only make the problem "real" to you. Negative reinforcement.
posted by Zambrano at 1:52 PM on October 20, 2008

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