What does the knee meniscus do?

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What does a knee meniscus do?  The knee meniscus acts as a shock absorber to help reduce wear and tear on the cartilage and bones of the joint.  It also helps to guide movement.  As has been discussed elsewhere in this web-site, we don’t have a lot of convincing data that surgically trimming the meniscus helps pain and function in the long-run.  In fact, in the two recently published studies it was shown to be no better than placebo or physical therapy/SynVisc shots. I think today’s case helps to illustrate what a meniscus does on a day to day basis.

This is a knee MRI from a 60 year old white male, one of last year’s study patients now at 13 month follow-up.  This is an interesting patient with good results in the right knee (MRI shown here) and no effects in the other knee (left, MRI not shown).   Upon beginning the Regenexx-C procedure, both knees had severe medial compartment degenerative joint disease with lots of swelling.  My review of the follow-up MRI’s of the left, non-responding knee showed only minimal changes, while the right responding knee showed the following changes.  Below are “saw you in half” MRI views from right to left (coronal).  The white circle shows the medial meniscus in a special MRI sequence known as a proton density, fat saturation taken on a 3.0 Tesla (ultra-high field) MRI magnet.  The ragged appearance of the meniscus has changed for the better (white dashed circle) and many of the smaller sub-chondral cysts in the bone look a bit better.  The real interesting finding is in the large yellow dashed circle.  The white hole there is a very big sub-chondral cyst.  This is essentially a fluid filled hole in the bone that got there because the meniscus below is not doing it’s job, so all the force is getting transferred to the bone above.  The bone isn’t designed to deal with this force.  The hole likely formed because the bone was getting so beat up that the number of cells being killed off in the bone exceeded it’s ability to repair itself.  However, in this imaging orientation (coronal) the hole seems to have gone away from the before to after pictures.  Again, this coincided with this knee feeling significantly better and his ability to walk or hike longer distances.  So why?

kl-knee-cor-pdfs

The big issue is whether you can still see the hole in another orientation.  After all, maybe the one coronal slice just missed the hole in the “after” image and just caught the middle of it in the “before” image.  These are the sagittal (“saw you in half” views from front to back) views below.  The yellow dashed line is again through the area of the cysts.  In the before, we see fluid filled cysts, the biggest to the right and like a family of cysts, the little children “cysts” trail off in size to the left.  The after image again doesn’t have the cysts.  So why?  The rest of the films on the right (after images) I think show why.  The white dashed circles on the left before image show a very jagged appearing meniscus.  The meniscus in this area should look like a dark and orderly triangle.  However, here, it looks like a wild thing that needs a haircut.  In essence, the before images show a meniscus in a very severe state of failure.

The 13 month after images to the right have the same images through the meniscus, now it doesn’t look jagged.  We also saw this same change in the meniscus in the 8 month follow-up images as well (not shown here).  The fact that the cysts have gone may be due to better function of this now “more tame” meniscus?  Well, the knee feels better on this medial side, the bone stress reactions (cysts and swelling in the bone) have gotten dramatically better, and the meniscus has gone form being beat up and frayed beyond belief to being nice and orderly again.

kl-knee-sag-pdfs1

The upshot?  When the meniscus functions, it protects the overlying cartilage and bone.  When it doesn’t work or when we take big pieces of it out, we see the underlying cartilage and bone get beat up.  Our experience and the research would state that removing parts of the meniscus may not be good idea.

This patient was treated with the Regenexx-C (cultured stem cell injections). It should be noted that not all patients with severe knee arthritis can expect to see this same type of result.

Learn about Regenexx procedures for knee conditions.
Chris Centeno, MD is a specialist in regenerative medicine and the new field of Interventional Orthopedics. Centeno pioneered orthopedic stem cell procedures in 2005 and is responsible for a large amount of the published research on stem cell use for orthopedic applications. View Profile

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NOTE: This blog post provides general information to help the reader better understand regenerative medicine, musculoskeletal health, and related subjects. All content provided in this blog, website, or any linked materials, including text, graphics, images, patient profiles, outcomes, and information, are not intended and should not be considered or used as a substitute for medical advice, diagnosis, or treatment. Please always consult with a professional and certified healthcare provider to discuss if a treatment is right for you.

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