RSSFUNCTIONAL ADAPTATIONS TO QUADRICEPS INHIBITION
September 23, 2009 by David Fitzgerald
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Filed under Movement Impairments, Physiotherapy Blog
The acknowledgement of quadriceps inhibition as a complicating factor in knee joint pathology is pretty much unquestioned in routine clinical practice. This is evident by the standard prescription of inner range quadriceps exercises as part of any post operative knee regime and also cases of knee pathology that do not require surgical intervention. My views on the appropriateness of inner range quadriceps as a primary strategy for quadriceps re-education are well known and have been discussed in previous posts (see Terminal Knee Extension) but suffice to say that I am not a big fan as I think there are more superior choices of exercise.
Compensatory Movement Patterns
In this discussion I want to review some of the compensatory movement patterns observed clinically which appear to be the result of poor quadriceps functioning:
1. Impaired terminal knee extension
- is the most obvious example and needs no further expansion here.
2. Compensatory hamstring hyperactivity
- this can be indicated by a persistence of hamstring tightness even when routinely stretched, indicative of an increased recruitment strategy. It may appear paradoxical but the literature is full of detail on quadriceps / hamstring co-activation (particularly the ACL rehabilitation literature). Not surprisingly the reciprocal activation of hamstring / quadriceps recruitment is not an on-off mechanism but a graded degree of simultaneous tension – consistent with all joint requirements for stability. It may be that the compression produced by hamstring activity is a compensatory strategy for compromised quadriceps contribution?
3. Hamstring dominance in active straight leg raise test
- the active straight leg raise test has been utilised as a measure of pelvic and groin dysfunction can also yield useful information regarding hamstrings / quadriceps activation.
I modify this test by bringing the patient into a straight leg raise position just short of hamstring tension and then request an active hold in this position.
Therapists can then observe two things:
A). A loss of terminal knee extension when under active control or
B) Determining the site of predominant muscle activity (asking the patient to report their predominant area of perceived effort) which in this situation will often point to the hamstrings.
Because the position of the test is short of full hamstring tension one cannot deduce that this perception of increased hamstring tension is due to a lack of elasticity.
4. Compensatory trunk flexion
in an attempt to maintain the length / tension relationship of the quadriceps. This is usefully measured in sitting with the establishment of a lumbar lordosis in an upright-seated alignment, feet off the floor. The patient is then asked to extend the knee. The frequent observation in this test is for the pelvis to posteriorly rotate producing trunk flexion.
In order to determine if this is a result of hamstring restriction or lack of active quadriceps control the therapist should try to passively extend the knee at the point at which the pelvis starts to posteriorly rotate. Increased mechanical resistance indicates posterior leg tightness; greater passive range indicates inner range quadriceps inhibition compensated by posterior pelvic rotation.
5. The hamstring – gastroc paradox
- this is a concept we have touched on before and one not frequently discussed in clinical circles – although sometimes alluded to in gait analysis. The crux of this theory is that the gastroc soleus complex acts with reversed origin / insertion activity with the ankle as the fixed point. Gastrocnemius contraction coupled with that of the hamstring produce a combined force, which tends to extend the knee.
In biomechanical terms this is the old ” parallelogram of forces” rule where two muscle groups crossing a joint from above and below act in a combined manner to extend the joint. This again can be tested clinically by utilising a stance position superimposing a ¼ – ½ range squat on the front leg. Palpation of dominant muscle activity is one way to try to determine predominant muscle activity and of course verbal feedback on dominant site of perceived effort is another.
In a previous discussion’s on extensor chain function we looked at the interaction between hip extension, knee extension and ankle plantar flexion as part of the basic propulsive mechanism. Obviously disturbances in the synergies of these primary muscle groups will compromise the efficiency of this movement pattern. The clinical challenge is to determine the site of increased stress and the mechanism of overload within the system. So many patients we see demonstrate an “Apropulsive (without propulsion) gait due to compromise of the extensor chain. As clinicians we need to be alert to recognise these mechanisms.
what observational gait parameters would give us clues about lack of propulsion in walking?
Enjoy the clinical challenge.
David
A very interesting post David. I agree on all counts. It is about time physios looked beyond simple leg extension exercises post operatively and otherwise in order to recover correct quads function.
With regards to your question, my thoughts would be, shortened stride length, increased knee flexion at heel strike (if heel strike is actually demonstrated), decreased speed of gait, decreased weight bearing time on affected side etc.
Hello Paul,
great to see you here, particularly with all that experience of chronic overuse lower limb injuries!
On functional implications of quadriceps impairment we can look at it from both a swing phase evaluation and also a stance phase. Undoubtedly, the quality of the swing phase will set you up for the stance element but it all depends on where you start from. If we think about propulsion at the termination of stance phase then the fundamental biomechanical requirement requires a relatively rigid lever for ground propulsion ie relative “stiffness” of lower limb while the ankle generates plantar flexion force in conjunction with hip extension and an extended knee.In reality the knee is not rigid and therefore a flexible link in the chain.
So apropulusion is evidenced be delayed/absent heel-off, terminal knee extension and end range hip extension. A forward inclination of upper body alignment contributes to lack of propulsion.
David