Knee Popping After Sprint

Question
Hello Robert,

I sprinted 10 times 50m each with resting time walking back to the starting point.

After the sprints When walking upstairs my left knee started to pop loud but there is no pain.

What can I do to stop the popping ?

I've been to ortho and he said I had meniscus tear that I don't belive he only felt it no MRI or X-Ray

How can I be sure do I have meniscus tear or I just over trained ?

Answer
First of all, I would like to make it clear that I am not a doctor.  If you have been diagnosed by a doctor that you have a meniscus tear, I'm not qualified to argue otherwise.  Even if I was a doctor, it would not be appropriate for me to counter this diagnosis without actually seeing you in person for a consult.

With that caveat out of the way, I can certainly talk about general reasons why people's knees might make loud popping sounds, which may or may not apply to you.

Many joints, including the knees, can produce cracking or popping sounds.  The familiar process of knuckle cracking is one such example.  The same process involved when you crack your knuckles can occur in your back, neck, knees, elbows, toes, and so on.  Interestingly, there is no consensus among scientists as to what actually causes this sound.  One theory is that it has to do with cavitation.  Cavitation is a physical process whereby the partial pressure of a liquid drops below its vapor pressure - the pressure at which it turns into a gas.  The most visible example of this is a spinning motorboat propeller.  Even though the propeller is completely under water, it often produces a trail of bubbles.  These bubbles are composed of water vapor that formed along the trailing edges of the propeller blade where the extreme pressure differential allowed them to form.  A similar process may occur in your joints as they are manipulated.  The formation of one or more bubbles, however, is silent.  What makes a sound is when the bubbles collapse and turn back into a liquid.  When this happens, a popping sound is produced.

Other theories relating to this sound include:

* A tendon snapping over bones
* A bone quickly jerking back into place
* Breaking of a joint seal with the release of a nitrogen bubble

A nice paper on this subject, in the Journal of the American Osteopathic Association, can be found here:

http://www.jaoa.org/content/102/5/283.full.pdf

It is worth pointing out that joint cracking is perfectly normal, and has never been shown to be deleterious to a joint.  Dr. Donald Unger regularly cracked the knuckles of his left hand for more than sixty years, but not his right.  No arthritis or other ailments formed in either hand, and he was awarded 2009's Ig Nobel Prize in Medicine.  So if your knee popping is a form of this common type of joint noise, you needn't worry about it.  If it does not cause pain, and you can live with the strange sound, it might be something that is normal for your body and not worth worrying about.

If your knee popping is due to one of the above mentioned harmless conditions, then you might be able to reduce its occurrence with proper training.  I have noticed over the years that some of my own joints that often made popping sounds stopping making noise as I went through rigorous training and development.  This is because strengthening the muscles and tendons around your joints leads to increased stability of the joints, which can sometimes change the underlying physics just enough to eliminate popping sounds.

In your case, you would need to engage in anaerobic, strength-conditioning exercises of your legs.  For example, one exercise you might consider is the barbell squat.  This exercise engages large numbers of muscles in the legs and is used by athletes to improve lower body strength.  (There are many, many other leg strengthening exercises you can also explore.)  Note that muscular growth is a slow process, so doing these exercises will not have an immediate effect.  It may take a few months for the surrounding leg structures to grow stronger.  But if this is the cause of your problem, then the frequency of popping should decrease with time.

However, I also need to point out that sometimes noisy joints are not harmless.  You might hear the term "crepitus".  This is a medical term to describe the grating, crackling, or popping sounds and sensations experienced under the skin and joints.  In some cases, it is perfectly normal.  However, in other cases it is indicative of injury.  For example, an osteoarthritic joint produces a grinding sound because the cartilage has eroded away and the bones of the joint are literally rubbing against one another.  Another example of crepitus is when a person has a bone fracture - the broken surfaces of the bones can rub together and produce a sound.  If your knee popping is the result of some underlying physical disease or injury, then it may take corrective surgery and/or a period of convalescence in order to eliminate the problem.  Note that doing things like barbell squats would be counter-indicative in this case - if your knee is damaged then these types of exercises could possibly worsen the injury.

One thing you can try without risk is a knee band.  This are small elastic straps that fit around your leg just under your knee.  They are sold online and in some drugstores for little money.  Knee bands compress the patellar tendon and decrease the stress on the tibial tubercle.  As with their cousins - elbow braces used for tennis elbow - this mild compression slightly changes the force vector of the affected tendon, which can make otherwise painful movements possible.  In your case, this might be just enough to stop the noise from occurring, assuming your problem is due to patellar (kneecap) related structures.  A knee band won't cause injury, and the cost is small.

As for your second question: "How can I be sure do I have meniscus tear?", according to the American Academy of Orthopaedic Surgeons (AAOS), the most common symptoms of meniscal tear are:

* Pain
* Stiffness and swelling
* Catching or locking of your knee
* The sensation of your knee "giving way"
* You are not able to move your knee through its full range of motion

So first of all, you should ask yourself if you have any of these symptoms.  If so, then you fit the profile of this injury.  If not, you may (or may not) have a meniscal tear.  According to the AAOS:

"One of the main tests for meniscal tears is the McMurray test. Your doctor will bend your knee, then straighten and rotate it. This puts tension on a torn meniscus. If you have a meniscal tear, this movement will cause a clicking sound. Your knee will click each time your doctor does the test."

Did your doctor do this test?  If so, then this might be why he felt comfortable diagnosing you as having a meniscus tear in lieu of an diagnostic imaging.  Note that meniscal tears do NOT show on x-rays, however, they can show on an MRI.

There are many different ways your knees menisci (there are two) can tear.  The outer third of a meniscus has a rich blood supply, and can often heal on its own or be repaired without surgery.  A longitudinal tear is an example of this kind of tear.  Conversely, the inner two-thirds of the meniscus lack a blood supply.  Tears in this part of the meniscus will not heal on their own.

If you do indeed have a meniscus tear, then your doctor should be able to diagnose it and determine if it is of the kind that may possibly heal on its own.  On the other hand, he might just as likely diagnose it as one of the types of tears that require surgery.  Once again, I'm not a doctor so I defer to your physician's judgement on this.  Of course I safely say that it never hurts to get a second opinion, especially where surgery is involved!  For more information, visit the AAOS web page on meniscal tears here:

http://orthoinfo.aaos.org/topic.cfm?topic=a00358