Discussion in 'Spot Diagnosis' started by danielmx, Dec 20, 2012.
recurrent knee pain in a 62 yo man
CPPD or Pseudogout
I have never disagreed with Dr. Gospodin Seki and I am going to happily agree with him again.
The X ray of the knee joint is one of the most common we will see and most will directly read the MD Radio's report and will never bother to correlate (i am by no means implying that they cud be wrong and that we shud cross check...they r among the smartest in our profession ). So I going to decode this and also touch upon OA ( degenerative )
The normal knee x ray shows a clear / radiolucent jont space becos both articular cartilage and menesci are radiolucent structures.
In the image posted by Daniel, the menesci are clearly calcified and it can be from a variety of causes which deposit ca in the joint space, like pseudogout ( cited by Mishary ) or Osteoarthritis ( degenerative or following acute trauma ) as cited by drusingh....and this calcium deposition from any cause would be included under the umbrella term - Chondrocalcinocis.
Now let's take a look at an osteoarthritic ( degenerative ) x ray.
You will notice that it's the medial compartment that's usually crushed and why is that so ?
to understand this, let's understand normal weight transmission (while walking ) first - 90 % of us have slight bow legs which causes the outside of the heel bone to strike first followed by a subtle in-rolling and slight flattening of the medial longitudinal arch. The mechanical reason for this physiological in-rolling is because our ankle joint (sub tibial ) is designed like a “Miter joint” which is inherently weak, but for a reason – so that the in-rolling gently shifts the weight to the medial longitudinal arch and causing it to flatten (slightly) thus dissipating the ground reactionary forces more ergonomically / physiologically and transfer of the weight upward slightly more thru the medial compartment of the knee as it is bigger and more in line with the hip joint....so that's normal.
But if either the angle of the Miter joint angle is exaggerated – like in somebody with excessive bowlegs or if the stabilizing factors like the ankle ligaments are torn/weak, the feet lands as if on a knife edge and the in-rolling is exaggerated resulting in complete flattening of the medial longitudinal arch causing and in this context it’s by no means subtle.....Multiply this into every minute, hour, day……and U know that it's a potential problem by itself.....
Also people who are obese will have excessive pronation on planting the feet while walking with consequent excessive flattening of the Medial longitudinal arch.....now most if not all of the weight will be transmitted upwards, through the medial compartment of the knee and this sets the stage for OA of the knee and it's sequelae ...all the way into the spine.
Relevance in today’s context – These days parents are very aggressive and what their kids to take their first baby steps by age 5 months, walk and fetch the tv remote by 7 months and burn the dance floor on the first birthday. I know of a couple that had infant walkers ready even before their child was born (not kidding…they had borrowed it from their relatives b4 somebody else borrowed it). Early walking with or without infant walkers sets the stage for bow legs which is further compounded if the child is on the wrong side of the weight curve( and extreme form of which is called Blount’s disease / tibia vara – for which early walking and childhood obesity is thought to be one of the causes). A heavier infant will start walking later compared to a lighter infant…but anxious parents and an overenthusiastic pediatrician ( I am not generalising, becos many pediatricians are also among the most intelligent in our field)who looks at milestones just as mere numbers can set the stage for early onset flat-foot and the sequelae.
There is another facet to this problem in our urban setup. Gone are the days when children would run around barefooted in the uneven courtyards, climb trees or jump over the school fence to play truant :-D. Urban toddlers walk bear footed in their homes (flat surface) or when outdoors walk mostly on asphalt (again flat surface) with flat shoes (if not being pushed or carried around). No scope for development of any muscle, let alone intrinsic foot muscles.
A comment on the ans by drusingh - Osteoarthritis...I think the medial joint space although not totally reduced is slightly obliterated and let's call it " the early stage of Degenerative OA", but the standout feature is still "Chondrocalcinocis".
And can we do something simple / practical to arrest or slow the development of OA in the obese population ?
we often tell them to lose weight - but if it's going to be open ckt ( foot leaves the surface), then all the pounding will accelerate the problem. So as far as wt loss exercise is concerned it should be closed ckt.
[Broken External Image]:http://exercisecycles.net/elliptical-bike.jpg
And here is something we can do immediately - prescribe a shoe that has a good insole to support the instep / medial longitudinal arch..it will help to redistribute some weight through the lateral compartment of the knee.
ANSWER: It is chondrocalcinosis which is considered in some sources as pathognomonic for pseudogout or calcium pyrophosphate crystal deposition disease
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