When the knee hinges sideways. A clinical video case.
This is not a difficult case today, not by any means. Most people will can see what is not normal here. But there are some simple principles we wanted to highlight and remind you of that this case shows nicely.
This is a fairly typical advanced degenerative arthritic right knee and the gait that accompanies it.
Here you can see that when the gentleman steps onto the right limb the knee has a small lateral hinge moment, you can see the knee joint buckle sideways. This is not normal, the knee is supposed to hinge only forward and backwards (flexion and extension) in the sagittal plane. Here it is hinging in the frontal plane. You can easily see that after many years of abnormal stresses that the tibia has deformed into a varus bowed position. This is a great example for you engineer-type out there about long term deformation of solids.
* Deformation of Solids:
- Stress: is a measure of the force required to cause a particular deformation.
- Strain: is a measure of the degree of deformation.
- Elastic Modulus: the ratio of stress to strain:
Elastic modulus = Stress divided by Strain or
EM= Stress / Strain
The lateral forces and hinging over time forced the tibial to varus bow which is a reactionary measure. In simplest of terms, as the bone cells (osteoclasts and osteoblasts) continued to cyclically turn over they laid down new osseous structure along lines of stress which happen to be in the frontal plane, hence the frontal plane bow. At the joint line it was simple to feel and advanced gapping and shifting of the joint in medial-lateral-medial stressing. One can only imagine the maceration of the cartilagenous menisci in such a knee from the abnormal shear forces. Oy !
In this gait, this joint is quite clearly painful as evidenced by the pronounced limp. As right limb weight bearing is initiated carefully and slowly to reduce pain and gain stable purchase of the limb with balance the lateral shift is seen to occur. This lateral shift challenges all of the frontal plane stabilizers so it should be no surprise to anyone that he has significiant gluteus medius, peroneal and abdominal weaknesses in guarding that right frontal plane (to name just a few).
It is most difficult to see on this video because of the loss of 3D specs and because we do not have a frontal view of this gait, but what you typically see in the gait of these clients is a normal left to right step length and an abbreviated right to left. As the brain loads that right limb there is pain and instability sensed by joint and pain receptors. This sparks an early and abrupt departure off of the right limb and hence an abbreviated and shortened right to left step length. This will impart a quick load onto the left leg with an abrupt loading into the left quadriceps. It is not uncommon at all for these clients to develop anterior knee pain syndromes (such as patellofemoral tracking syndromes) or foot problems because of repeated abrupt mid-forefoot loading which drives significant of calf-posterior compartment loading (this will also drive long toe flexor strategies). Also, an abrupt right to left weight bearing shift will generate excessive left lateral (frontal plane) forces thus it is not uncommon to show or develop left hip issues or to see more sustained supination of the left foot. The Peronei can be challenged too to fend off this over-supination that can frequently occur.
* clinical pearl: In our clinics when we see a one sided increase in toe clench and long flexor tone, even when the client lies down, we will once again review gait and look and test for clinical instabilities of stance phase mechanics on the OPPOSITE side of the long toe flexor evidence (in this case there was increased left long toe flexor evidence and early hammer toe formation). This is a huge key, we have just sold a few acres of the farm giving away this pearl. This is one of our goto tricks to find deeper embedded clinical problems. It is not always the case, because the long flexor problem can be local or same sided but you have to at least consider the thought we have proposed.
This is the exact same gait pattern as in a sprained ankle, in fact, same pattern when any part of a limb is painful. As you leave the healthy left foot the brain already knows that right foot impact is going to be painful so a pre-calculation is make to soften the loading and to reduce the loading time, hence the premature limp off the right and onto the left.
It is also important in these cases of significant unilateral bow/varum of the tibia to investigate whether a true leg length discrepancy has developed. It can be a part of the visual limping/lurching gait but it is part of the deformation of the tibia. In this case we ended up using a 3mm sole lift (don’t use a heel lift, why would you just raise the heel ?) to level out his pelvis to decrease the frequent low back pain and tightness that goes with such a gait and also to reduce the step-down drop onto that degenerative knee. In this case, the lift reduced the degree and rate of lateral hinge and thus reduced much of his pain and back discomfort. By bringing the ground up to his foot he thus did not have to step down onto the right limb which accelerates the lateral shift.
* Try it yourself, find a curb on your street and walk along the top surface of the curb with the left foot, stepping down onto the right foot to street level. Do this for a year and you would quickly appreciate what this gentleman was experiencing daily……to a degree of course. The lift on the right would be warmly welcomed !
We were actually able to keep the client very comfortable for almost a year which got him to a time frame that worked for his work and vacation time frame to have the surgery. This is often what a client needs, time. Just time to plan, to prepare mentally for a TKA (Total Knee Arthroplasty (replacement)).
The laterally hinging knee. It is so much more than just a degenerative joint. There is much to be appreciated and learned from pathologic gait patterns.
We are…… Shawn and Ivo…… The Gait Guys ……. center focused but considered by many to be a little off plumb.
