Case of the Week 24/11/97: What people said...

Dear all,

A spurt of conscience on a Saturday morning reminded me that the current Case of the Week (65 yo right hemiplegia) at:


remains un-analysed. I'd hate Andreas' hard work to go wasted, so here goes...

Observational: apropulsive, short-stride, excessive trunk flexion during left stance. Fixed right knee and possible right hip flexion contracture. Left hemipelvis leads. Hip-hiking and some circumduction to allow clearance. Contact with both feet is antero-lateral - right is externally-rotated.

Kinematics confirms these, but also note that the "unaffected" left knee is also hyperflexed. Both ankles are dorsiflexed, too, with a lengthened stance phase on the left (unaffected side). Velocity, cadence and stride length all very low.

Kinetics confirms weak push-off on both sides. Hip frontal moment and powers are very much diminished. Strong hip extensor moment through stance on the unaffected (left) side.

I confess that I can't make much of the Electromyography, which was recored with an old version of the Vienna Noraxon system. Anterior tibials are active rather early on the hemiplegic side (during "push-off"), which can't help. If anything, the left hamstrings are more active in stance.

The puzzling thing to me is why his unaffected left knee is held in a flexed position, and why the left ankle is held dorsiflexed. Are these, I wonder, compensations to keep the body centre of mass low, since the right side is unable to raise it? I guess this would conserve energy.

I hope some physios out there will comment on this.

Incidentally, we're currently working on automatising the Case of the Week page with a CGI script. I'll let you know when it's finished.

Look forward to your feedback,

Chris -- Dr. Chris Kirtley (Kwok Kei Chi) MD PhD Assistant Professor Department of Rehabilitation Sciences The Hong Kong Polytechnic University

Hello, this is Dr. Sang-hyun Cho at S-Korea. I am so pleased that I am writing to cga-listserve again. But I am really sorry that works of Dr. Kirtley and Dr. Andrea seems to be not appreciated properly.

Here is my opinion for the last "case of the week: right hemiplegia".

1. What's his main problem?

Of course it is his paralyzed right leg. But it seems to me that his left hamstring has become rather tight which is his second main problem. Such mild-to-moderate tightness on the non-paralyzed side is so easy to happen and so easy to be prevented, as well in Rehab. hospitals. That is because the hamstring, as a two joint muscle, is the first one to be shortened "even in the normal people" after very limited time of standing or walking in daily activities. Even if the shortening is usually not evident as a knee joint contracture, it does affect upright position for walking. Especially, the hip flexion and knee extension for the initial contact is just contrary to the action of the hamstring. So, the shortened hamstring demands flexion of the knee since the start of the stance phase.

* The sequence how the shortened left hamstring affected his gait.

a) flexed knee joint in early stance causes the GRF(ground reaction force) line to be passing anterior to the hip joint center and posterior to knee center and anterior to the ankle center. b) COM(center of mass) of the body shifts backward endangering the standing balance. c) in order not to fall backward, the trunk should be drawn forward. d) so the hip flexion and ankle dorsiflexion increased. e) but those unwanted flexion should be under control, as much as possible, in order not to collapse on the ground. f) so the left hip extensor moment, knee extensor moment, and the ankle plantar flexor moment(late) during the stance phase increased. g) at pre-swing period, the left plantar flexor become very stretched. According to the length-tension relationship in muscle physiology, such pre-stretched muscle can not exert its maximal contraction power. So, the push-off power of the left ankle decreased.

2. Is there evidence of co-contraction on the EMG?

Yes. At the end of the swing phase, the agonist-antagonist couples of Lt. hamstring-quadriceps and Lt. GCM-TA shows co-contraction.

a) quadriceps: because the hip flexor power is not enough to make proper hip flexion during the swing phase, the rectus femoris (one of the quadriceps, also a two joint muscle) helps it. It means abnormal lengthening of firing time in rectus femoris causing co-contraction with hamstring in terminal swing period. b) GCM: when the pre-stretched muscle is stretched more, protective monosynaptic reflex at spinal cord level is prone to occur especially in de-centralized(CNS problem) muscles. When this patient tried to raise up the toes for terminal swing by TA, the pre-stretched GCM became more stretched, and its reflexive firing appeared as a co-contraction.

3. Is the presence of co-contraction a significant problem for inverse dynamics modeling ?

Well, I'm afraid I don't know. Because I do not have proper understanding in inverse dynamics modeling.

-- Sang-hyun Cho MD.PhD.(Rehabilitation medicine specialist) Full time lecturer at Dept. of Rehabilitation Therapy Yonsei University Wonju campus, College of Health Science Wonju-si, Kangwon-do, ZIP 220-710, Rep. of KOREA * *My home page= *Owner of rehab-kr mailing list at

Today, I read the following book which reminded me of the last "case of the week: Rt. hemiplegia" at /archives/21-11-97

"Uncertainty in the person's ability to control and balance the body may cause the subject to protectively lower the center of gravity, even though this may require greater energy or promote further loss of balance... People who attempt to walk in a dark and unfamiliar place usually tend to flex at the hips and knees, as do patients who are unsure or frightened." ( Smith LK, Weiss EL, Lehmkuhl LD: Brunnstrom's clinical kinesiology, 5th ed.FA Davis company, 1996, p51 )

As Dr. Kirtley mentioned in his answer, I think that we should think about the question; "Do hemiplegics lower their COG by flexing the good hip and knee joint for better balance ?" And I would like to present the following topics for further discussion.

Reviewing papers about this topics will be worthwhile for our CGA mailing list.

With my best regards,

Sang-hyun Cho MD.PhD.(Rehabilitation medicine specialist) Full time lecturer at Dept. of Rehabilitation Therapy Yonsei University Wonju campus, College of Health Science Wonju-si, Kangwon-do, ZIP 220-710, Rep. of KOREA * *My home page= *Owner of rehab-kr mailing list at

Writing in regards to the 65 yo person with right hemiparesis. The knee flexion on the noninvolved side perhaps could be caused by one of several factors (or an interaction between them)

Through clinical observation (I havent seen any research specific to this topic) I have noticed an interesting phenomemon in the amputee population. One of the biggest difficulties new AK (TF) amputees have is foot clearance during swing. Consequently, the prosthetist or PT or MD, recommend shortening the prosthesis to facilitate clearance in swing. It has been my experience that this is not usually effective. It seems that the pt automatically adjusts to level their pelvis, ie, the more length removed from the prosthesis, the more the pt functionally shortens the sound limb by flexing the knee in stance. Do you think that what we see in the hemi in the case study could be a adjustment by the pt to level the pelvis? I would be interested in hearing everyones thoughts.

Scott Bleakely <>

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