Foot orthoses and rearfoot/tibia coupling patterns

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Effect of foot orthotics on rearfoot and tibia joint coupling patterns and variability. (http://www.jbiomech.com/article/PIIS0021929004002210/abstract)

J Biomech. 2005 Mar;38(3):477-83
Ferber R, Davis IM, Williams DS

The purpose of this study was to compare joint coupling patterns and variability of the rearfoot and tibia during running in subjects who were treated with two types of orthotic devices to that of controls. Eleven subjects with various lower extremity injuries were treated unsuccessfully with a standard orthotic, and then successfully with an inverted orthotic. Three-dimensional kinematic data were collected while subjects ran without orthoses and then in standard and inverted orthoses. Eleven healthy subjects ran without orthoses for comparison. The rearfoot inversion/eversion and tibial internal/external rotation joint coupling pattern and variability relationship was assessed using a vector coding technique. It was hypothesized that when the treated runners ran without orthotic devices, they would exhibit lower joint coupling angles and lower joint coupling variability compared to the controls. In addition, it was hypothesized that there would be no difference in the coupling angle or coupling variability between the standard and no orthotic conditions of the treated runners. Finally, it was hypothesized that coupling angle would decrease and variability would increase in the inverted versus the standard and non-orthotic conditions. No significant differences in joint coupling pattern or variability were observed between the treated and control subjects. In addition, no significant differences were noted between the orthotic conditions in the treated group. These results suggest that foot orthotic devices do not produce significant changes in rearfoot-tibial coupling. Therefore, the relief experienced with the inverted orthotic is likely due to factors other than alterations in this coupling.

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Forefoot, rearfoot and shank coupling: Effect of variations in speed and mode of gait.
Gait Posture. 2006 Jun 4; (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?tmpl=NoSidebarfile&db=PubMed&cmd=Retrieve&list_uids=16759862&dopt=Abstract)
BACKGROUND: Although there is a wealth of research into the kinematic coupling between the foot and shank, it remains unclear whether the relationship is stable across speed and mode of gait. The aim of this study was to determine whether the coupling relationship between the forefoot, rearfoot and shank differed between walking and running, and across different running speeds.

METHODS: Twelve subjects walked/ran barefoot over-ground at one walking and three running speeds. The shank, rearfoot and forefoot were modelled as rigid segments and three-dimensional joint kinematics were determined using a seven camera ProReflex system. Coupling between the forefoot, rearfoot and shank was assessed using cross-correlation and vector coding techniques.

FINDINGS: Cross-correlation of rearfoot eversion/inversion with shank internal/external rotation was lower in walking (r=0.49) compared to running (r>0.95). This was also the case between rearfoot frontal plane and forefoot sagittal plane motion (walking, r=-0.80; running, r=-0.96). Rearfoot frontal plane and forefoot transverse plane cross-correlation was high in both running and walking (r>0.90), but there was little evidence of any coupling between rearfoot frontal plane and forefoot frontal plane motion in any condition. No differences in cross-correlations were found between the three running speeds.

INTERPRETATION: Kinematic coupling between the forefoot, rearfoot and shank was weak during walking relative to running. In particular, the low cross-correlation between rearfoot eversion/inversion and shank internal/external rotation during walking implies the two motions are not rigidly linked, as has been assumed in previous injury models.

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Discrete and continuous joint coupling relationships in uninjured recreational runners.
Dierks TA, Davis I.
Clin Biomech (Bristol, Avon). 2007 Mar 14 (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?tmpl=NoSidebarfile&db=PubMed&cmd=Retrieve&list_uids=17367903&dopt=Abstract)
BACKGROUND: Abnormal joint coupling is thought to be related to overuse injuries in runners. However, researchers do not yet know what constitutes normal joint coupling during running, which makes abnormal coupling difficult to define.

METHODS: Lower extremity kinematics were collected from 40 recreational runners during stance. Joint coupling methods were applied and, for each method, means and both within- and between-subject variability were calculated. The 95% confidence interval was used to compare differences across coupling relationships and periods of stance.

FINDINGS: Timing between rearfoot eversion, tibial internal rotation, and knee flexion were relatively synchronous while relationships involving knee internal rotation were more asynchronous. The excursion ratios showed that every 2 degrees of rearfoot eversion was coupled with 1 degrees of both tibial internal rotation and knee internal rotation. Vector coding results showed that just beyond maximum loading, all joint coupling relationships resulted in relatively equal amounts of motion, while the within-subject variability was similar throughout stance. The continuous relative phase results showed that the most out-of-phase coupling occurred in the periods around heel-strike and toe-off while the most in-phase coupling occurred in the period just beyond maximum loading of the leg. The continuous relative phase within-subject variability was greatest at the periods around heel-strike and toe-off and smallest just beyond maximum loading.

INTERPRETATION: With a better understanding of joint coupling in uninjured runners, these data will help to serve as a reference for future studies investigating the relationship between running injuries and abnormal joint coupling.

[efuller]

Discrete and continuous joint coupling relationships in uninjured recreational runners.
Dierks TA, Davis I.
Clin Biomech (Bristol, Avon). 2007 Mar 14 (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?tmpl=NoSidebarfile&db=PubMed&cmd=Retrieve&list_uids=17367903&dopt=Abstract)

INTERPRETATION: With a better understanding of joint coupling in uninjured runners, these data will help to serve as a reference for future studies investigating the relationship between running injuries and abnormal joint coupling.

It's hard to call the idea that coupling of tibia and calcaneus motion are related to injuries a full fledged theory. It is more of simple research question without a guiding theory. Why would movement coupling be related to injuries? We could also look to see if toe nail length is related to injuries as well. It seems like a shot in the dark to research this question. Maybe there is more theory in the full paper.

It is easier to look at motion instead of forces and moments, but we may just find out that motion does not correlate with injuries. That would be my prediction based on the tissue stress approach. This research is also trying to establish a normal. Does being normal prevent injury? Hopefully, we can get research showing that motion doesn't correlate with injury so we can move on to looking at forces and moments. I would predict that forces on anatomical structures will correlate wtih injury.

Cheers,

Eric Fuller

[Kevin Kirby]

INTERPRETATION: With a better understanding of joint coupling in uninjured runners, these data will help to serve as a reference for future studies investigating the relationship between running injuries and abnormal joint coupling.

It's hard to call the idea that coupling of tibia and calcaneus motion are related to injuries a full fledged theory. It is more of simple research question without a guiding theory. Why would movement coupling be related to injuries? We could also look to see if toe nail length is related to injuries as well. It seems like a shot in the dark to research this question. Maybe there is more theory in the full paper.

It is easier to look at motion instead of forces and moments, but we may just find out that motion does not correlate with injuries. That would be my prediction based on the tissue stress approach. This research is also trying to establish a normal. Does being normal prevent injury? Hopefully, we can get research showing that motion doesn't correlate with injury so we can move on to looking at forces and moments. I would predict that forces on anatomical structures will correlate wtih injury.

Cheers,

Eric Fuller

I was thinking the same thing when I read this research, Eric. Why is coupling or "non-coupling" such an important idea?? I don't have a clue.

I can see that coupling is an interesting kinematic phenomenom to study but my guess is also that coupling will not correlate to injury production, like nearly all the other foot and lower extremity kinematic patterns studied by researchers.

Probably the reason that many things are studied in biomechanics is because they are easy to study given the equipment the researchers have at their disposal.

I would think that if researchers are truly interested in understanding the etiology of injury better, they should focus on external and internal forces and moments, not strictly on kinematics. I believe that the literature to date bears this out quite nicely.

However, knowing Irene Davis's body of research to date, she has probably contributed about as much to our knowledge regarding kinetics of foot and lower extremity function as anyone has. So maybe this is just an interesting subject for her and her coworkers to look at to see if anything significant is occurring....like throwing a line in the water to see if you get a bite?

[David Smith]

Kevin and Eric

What is meant by the terms - Joint coupling, non coupling, continuous coupling, In and ou of phase coupling, discreet coupling?

Thanks Dave

[David Smith]

Eric

It is easier to look at motion instead of forces and moments, but we may just find out that motion does not correlate with injuries. That would be my prediction based on the tissue stress approach.

Hear hear!

It does not seem a very difficult concept to understand that motion of a joint does not indicate potential to injury, unless the range is beyond the maximum physiological range.

EG If I arm lock the right arm of a person in a wrestling bout then I attempt to move their elbow joint beyond its physiological range, submission or injury will result. The moments about the joint are = to X and force on the olecranon process is quite high with the straight arm but if the arm is bent then there is no force on the OP even though there may still be the same moments of X magnitude about the joint. However there now will be much higher stress in the flexion mucles, which may be strained / traumatised at some point. If the opponent now takes hold of the right arm with his left hand and adds an external flexion force about the right elbow then he can reduce the internal stress in the right flexors. The position of the right arm can remain the same however.

The same applies to the foot by adding a FFO we can apply additional external forces and thereby reduce internal forces without changing joint position. Not only that but since the external forces are finite then by designing the FFO to apply more force at one point of interest it must decrease the force applied at another.

If we were to look at injuries to passive tissues such as bone and ligament that occcur when the joint reaches its physiologcal max range then it may be we need to consider the accuracy of the measuring devices.
The ligamnets of a joint are very stiff as is the bone and cartilage and therefore very small changes in length will equal large changes in internal stress. I do not believe it is possible to reliably measure, in vivo, such small differences in joint position that might be neccesary to reduce injury to the passive structures such as ligamnets. Do you agree?

All the best Dave Smith

[Kevin Kirby]

Kevin and Eric

What is meant by the terms - Joint coupling, non coupling, continuous coupling, In and ou of phase coupling, discreet coupling?

Thanks Dave

The basic idea of "coupling", as it applies to the tibia and rearfoot, is that tibial internal rotation should occur with rearfoot eversion and tibial external rotation should occur with rearfoot inversion during weightbearing activities. This is related back to the old idea that the STJ is a fixed hinge that should allow constant ratios tibial internal-external rotation/rearfoot eversion-inversion during these activities. However, we know now that the STJ is not a fixed hinge, that the STJ axis is polyaxial changing in spatial location continously during gait and that the tibia may rotate on the talus within the transverse plane up to 10 degrees without the talus moving.

If tibial internal-external rotation/rearfoot inversion-eversion occurs in a pattern that has a fairly constant ratio of tibial to rearfoot movement, then those motions are said to be "coupled". However, if rearfoot inversion-eversion occurs without corresponding tibial internal-external rotation, or if tibial internal-external rotation occurs without corresponding rearfoot inversion-eversion then these motions are said to be "non-coupled". "Continuous coupling" probably refers to coupling occurring over a certain period of time during gait. I am not sure what "in and out of phase" or "discrete coupling" are.

Hope this helps.

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Changes in foot and shank coupling due to alterations in foot strike pattern during running
Michael B. Pohla, John G. Buckley
Clinical Biomechanics (Articles in press) (http://www.clinbiomech.com/article/PIIS0268003307002227/abstract)
Background. Determining if and how the kinematic relationship between adjacent body segments changes when an individual’s gait pattern is experimentally manipulated can yield insight into the robustness of the kinematic coupling across the associated joint(s). The aim of this study was to assess the effects on the kinematic coupling between the forefoot, rearfoot and shank during ground contact of running with alteration in foot strike pattern.

Methods. Twelve subjects ran over-ground using three different foot strike patterns (heel strike, forefoot strike, toe running). Kinematic data were collected of the forefoot, rearfoot and shank, which were modelled as rigid segments. Coupling at the ankle-complex and midfoot joints was assessed using cross-correlation and vector coding techniques.

Findings. In general good coupling was found between rearfoot frontal plane motion and transverse plane shank rotation regardless of foot strike pattern. Forefoot motion was also strongly coupled with rearfoot frontal plane motion. Subtle differences were noted in the amount of rearfoot eversion transferred into shank internal rotation in the first 10–15% of stance during heel strike running compared to forefoot and toe running, and this was accompanied by small alterations in forefoot kinematics.

Interpretation. These findings indicate that during ground contact in running there is strong coupling between the rearfoot and shank via the action of the joints in the ankle-complex. In addition, there was good coupling of both sagittal and transverse plane forefoot with rearfoot frontal plane motion via the action of the midfoot joints

[Bruce Williams]

Eric

Hear hear!

It does not seem a very difficult concept to understand that motion of a joint does not indicate potential to injury, unless the range is beyond the maximum physiological range.


All the best Dave Smith

David;

I think the motion of a joint below maximum phsyiological range can make a determination towards potential injury. Problably not so much at the joint measured, but potentially to any joint immediately proximal or distal to the joint with the limited ROM.

I find that many knee problems are related to a decrease ROM in DFion at the AJ causing early heel off and early knee flexion.

Sincerely;
Bruce