Anterior meniscofemoral impingement syndrome.  Ever heard of it ? Probably not.

Here we have a case of a young fellow with knee pain immediately below the patellae. As you can see here there are a few issues, some of which he will likely grow out of and some of which he may not.  Here we obvious see hyperextension of the knees and increased ankle plantarflexion posturing (I chose that word carefully) that obviously goes hand in hand with this retro-postured knees.

After a few more questions it was clear that the pain had been around for quite some time and was at a specific pencil eraser sized area above the anterior joint line, slightly medially to center and without question not at the joint line proper but directly on the medial femoral condyle.  There was no swelling or fulness to suggest this was involvement of Hoffa’s fat pad. The patellar tendons were not thick. So, do you know what he has ?  You should always suspect this in knees that hyperextend this far or in athlete that have sustained or repetitive hyperextension stressing:

  • gymnastics
  • kicking sports (martial arts, soccer, swimming etc)
  • postural syndrome folks (like this little fella) who have low core tone, anterior pelvic tilt both of which drive knee hyperextension.
  • any one who has a loss of ankle rocker dorsiflexion range and who then chooses the knee hyperextension option to regain ankle range in an attempt to normalize progressive gait. Frequently flatter feet/hyperpronators will drive more tibial internal spin resulting in hyperextension as well.
  • short quadriceps with a dominant quadriceps strategy to control the hip and knees

This fella has several factors here.

So, clearly understanding these biomechanical factors and coupling a palpatory tenderness at the correct spot on the medial femoral condyle indicates that he has (the youngest we have ever seen)…….drum roll…….

Anterior meniscofemoral impingement syndrome.  Ever heard of it ? Probably not. Why, because it was glazed over in school, and maybe not at all for many doctors to be honest. Go ahead, look it up under Pubmed and see how many referenced papers you find on it.  I see it enough (albeit still rarely) to know that it is frequently diagnosed as a patellar tracking problem but those clients do not have the same risk and anatomy factors that I discussed above. I have had doctor referrals call me back saying they have never even heard of it, most have not to be honest.  Bottom line, if you know your anatomy and your biomechanics you can figure out most things. If you are slim and skinny on either one you might be missing a few things.  I do sometimes as well; we are all students.

Summary:  When the knee hyperextends either too much, too long, or for too many repetitions either statically or in dynamic walking, running or in activity the leading upper edge of the medial meniscus can impinge repeatedly and forcefully into the soft medial femoral articular cartilage and over time create a softening of the cartilage (chondromalacia ).  Do it long enough or enough times and you create an inflammatory reaction with a cartilagenous defect.

This poor little guy was hating walking.  Interestingly, what do you think happened when we had him crouch walk (knees flexed)……yup…..no pain. He looked up at me in wonderment immediately and of course saw me smiling knowing very well he would be pain free.

Solution in a 4 year old.  Slightly flex the knees and place a long strip of tape down the back side of the upper and lower leg.  If he extends the knee he forces the tape taught and is instantly reminded (pseudo biofeedback if you will) that he is approaching the danger zone. As this case and many other find, after a few days the skin gets pretty irritated but that is time to take the tape off and let him go back to his old tricks……. trust us, it is only for a few hours until he will figure it out……meaning….. hyperextension is evil ! Teaching this little guy our now famous “Shuffle walks” (to drive ankle dorsiflexion strength in the tibialis anterior and toe extensors in a posture of knee flexion) was on the menu to improve ankle dorsiflexion and anterior compartment strength and we turned it into a fun game for him to play with mom and dad.

Anterior Meniscofemoral Impingement Syndrome.  Say it 3 times fast with a mouthful of organic chunky peanut butter for fun. 

Hope you never see it in a little one. if you do, smile and reach for some tape and put on some 70’s music and shuffle to some oldies.

Dr. Shawn Allen,  one of the gait guys

Arthroscopy.

1996 Dec;12(6):675-9.Meniscal impingement syndrome.

McGuire DA, Barber, Hendricks

.Plano Orthopedic and Sports Medicine Center, Texas, USA.

Abstract

The meniscal impingement syndrome consists of three elements: impaction on theanterior medial femoral condyle by the leading edge of the medial meniscus, articular cartilage damage of at least Outerbridge grade 3, and knee hyperextension of at least 5 degrees. This report reviews this condition in a series of seven knees with an average follow-up of 39 months. The time from the onset of symptoms until surgery averaged 45 months. Treatment consisted of a thorough arthroscopic knee evaluation and debridement of the articular cartilage fragmentation and any impinging synovitis. Postoperative rehabilitation includes extension block bracing, hamstring strengthening, and closed-chain exercise. With this regimen, there was improvement in the Tegner scores and a reduction in postoperative knee hyperextension. Identification of this uncommon condition requires a complete evaluation of the medial femoral condyle in patients with knee hyperextension.

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