Get your foot in High Gear!

image source: Foot Orthoses and Other Conservative Forms of Foot Care. Michaud 1997; Williams an Wilkins: with permission

When it comes to gait, getting the 1st ray to the ground is the name of the game. When weight travels through the medial forefoot and we are able to push off the 1st ray complex, that is called "high gear push off". This was 1st discussed F Bojsen-Møller in this excellent paper (1), that just happens to be a free full text! Craig Payne, The Running Research Junkie has offered and excellent commentary on the topic here as well.

High Gear Push Off can happen when 3 conditions are met: 

1. we have a intact visual, vestibular and kinesthetic systems that ensure we can remain upright in the gravitational plane.
2. we have an intact calcanocuboid locking mechanism
3. we have adequate skill, endurance and strength of our extensor hallucis brevis

The 1st condition is more global and ensures that our cerebellum and vestibular apparatus are playing nice together to create balance, of the literal sort, We seek to keep our visual axes parallel and our center of gravity over our foot. Remember that the BODY will move itself AROUND the visual axes. If the axes are off, the brain will tilt the head and the body will move AROUND the head to accommodate. We have talked about that in these posts here on the blog. 

The 2nd condition, the calcaneo-cuboid locking mechanism, works in the coronal plane and relies on a functioning peroneal group, where the peroneus longus and brevis wrap around the lateral malleolus, cuboid and tail of the 5th metatarsal, crossing the foot diagonally to insert on the base of the 1st metatarsal. When working properly, its actions will be to plantar flex and everting the forefoot, lowering the 1st ray complex down and assisting the shift of the center of gravity more medial for the weight to pass through the medial foot and out through the hallux (ideally). 

The 3rd condition, the ability to descend the 1st ray, relies on the actions of the peroneus, appropriate supination of the forefoot and ability of the extensor hallucis brevis to do its job.  Because the tendon travels behind the axis of rotation of the 1st metatarsal phalangeal joint, in addition to providing extension of the proximal phalynx of the hallux, it can also provide a downward moment on the distal 1st metatarsal (when properly coupled to and temporally sequenced with the flexor hallicus brevis and longus). If the axis of motion for the 1st metatarsal phalangeal joint moves posteriorly, to behind (rather than under) the joint, the plantar pressures increase at MTP’s 4-5 and decrease at the medial mid foot, moving you into low gear push off.  If moved even further posteriorly, the plantar pressures, and contact time in the mid foot and hind foot (2). For more on the extensor hallucis brevis, see our post here.

As you can see, high gear is desirable over low gear push off, but sometimes circumstances or biomechanics do not permit. High gear push off ensures the forefoot is dorsiflexed and everted with respect to the rearfoot and the calcaneocuboid and talonavicular joint axes are perpendicular to one another, giving us a rigid lever to push off of as the center of gravity moves medially across the foot. In low gear push off, the foot is inverted and plantarflexed and the stress falls on the lesser metatarsals and lateral stabilizing complex of the ankle, moving the center of gravity laterally, in addition to the calcaneocuboid and subtalar joint axes being more parallel,  creating a less rigid lever for push off and decreased mechanical efficiency.

1. Calcaneocuboid joint and stability of the longitudinal arch of the foot at high and low gear push off. J Anat. 1979 Aug; 129(Pt 1): 165–176.  link to free full text: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1233091/

2. van der Zwaard BC1, Vanwanseele B, Holtkamp F, van der Horst HE, Elders PJ, Menz HB Variation in the location of the shoe sole flexion point influences plantar loading patterns during gait. J Foot Ankle Res. 2014 Mar 19;7(1):20.

The Adductor Magnus; Not just for adduction anymore...

Yet another paper (1) to support the notion that the adductors (particularly the adductor magnus, in this paper), act as external rotators (especially eccentrically), not internal rotators as is commonly purported in many anatomy texts (2) . Remember that the lower extremity is internally rotating (as a whole) from initial contact to midstance and externally rotating from midstance to pre swing. SOMETHING needs to help attenuate some of that internal rotation (and pronation) that occurs during the 1st part of stance phase and assist in external rotation (and supination); now you can add the adductor magnus to the popliteus, deep six external rotators, anterior and posterior compartments of the lower leg to the hamstrings and quads.

"This study suggests that adductor magnus has at least two functionally unique regions. Differences were most evident during rotation. The different direction-specific actions may imply that each segment performs separate roles in hip stability and movement. These findings may have implications on injury prevention and rehabilitation for adductor-related groin injuries, hamstring strain injury and hip pathology."

1. Benn ML, Pizzari T, Rath L, Tucker K, Semciw AI1 . Adductor magnus: An emg investigation into proximal and distal portions and direction specific action. Clin Anat. 2018 Mar 9. doi: 10.1002/ca.23068. [Epub ahead of print]

2. Leighton RD. A functional model to describe the action of the adductor muscles at the hip in the transverse plane.Physiother Theory Pract. 2006 Nov;22(5):251-62.



 

What did you notice? The Devil is in the details...

 Cavus foot? Loss of the transverse arch? Prominence of extensor tendons?

The question is: Why?

It’s about reciprocal inhibition. The concept, though observed in the 19th century, was not fully understood and accepted until it earned a Nobel prize for its creditor, Sir Charles Sherrington, in 1932. Simply put, when a muscle contracts, its antagonist is neurologically inhibited, So when your bicep contracts, your tricep is inhibited. This holds true whether you actively contract the muscle or if the muscle is irritated (causing contraction).

So how does this apply to this foot?

We see prominence of the extensor tendons (particularly the extensor digitorum brevis EDB; the longus would have caused extension at the distal interphalangeal joint). The belly of the muscle is visible, telling us that it is active. It is neurologically linked to the flexor digitorum brevis (FDB). This muscle, in turn, has slips which attach it to the abductor hallucis brevis (AHB) medially and the abductor digiti minimi (ADM) laterally. These muscles together form 2 triangles (to be discussed in another post) on the bottom of the foot, which lend to the stability of the foot and the arches, especially the transverse.

When the EDB fires, it inhibits the FDB, (which, in addition to flexing the MTP’s, assists in maintaining the arch). The EDB has an effect which drops the distal heads of the metatarsals as well (Hmm, think about all the people with met head pain) Now, look at the course of the tendons of the EDB. In a cavus foot, there is also a mild abductory moment, which flattens the arch. Conversely, the FDB in a cavus foot would serve to actually increase the arch, and would have a ,mild adductory moment. Net result? A flattened transverse arch.

Now look at the Flexor digitorum longus, overactive in tbis foot (as evidenced by the flexion of the distal interphalangeal joints, mild adduction of the toes (due to the change of direction of pull in a cavus foot) and lowering of the met heads due to hyperextesnion at the MTP joints ). This mm is reciprocally linked with the extensor digitorum longus. The prominence of the extensor tendons is do to increased activity of the EDB (go ahead, extend all your fingers and look at the tendons in your hand. Now flex the  DIP and IP joints and extend the MTP; see how they become more prominent?).

Reciprocal inhibition. It’s not just for dinner anymore…

We are and remain; The Gait Guys

Functional Ankle Instability and the Peroneals

Lots of links available here with today’s blog post. please make sure to take your time and check out each one (underlined below) 

As you remember, the peroneii (3 heads) are on the outside of the lower leg (in a nice, easy to remember order of longus, brevis and tertius, from top to bottom) and help to stabilize the lateral ankle. The peroneus brevis and tertius dorsiflex and evert the foot while the peroneus longus plantarflexes and everts the foot. We discuss the peroneii more in depth here in this post. It then is probably no surprise to you that people with ankle issues, probably have some degree of peroneal dysfunction. Over the years the literature has supported notable peroneal dysfunction following even a single inversion sprain event. 

Functional ankle instability (FAI) is defined as “ the subjective feeling of ankle instability or recurrent, symptomatic ankle sprains (or both) due to proprioceptive and neuromuscular deficits." 

Arthrogenic muscle inhibition (AMI) is a neurological phenomenon where the muscles crossing a joint become "inhibited”, sometimes due to effusion (swelling) of the joint (as seen here) and that may or may not be the case with the ankle (see here), or it could be due to nociceptive input altering spindle output or possibly higher centers causing the decreased muscle activity. 

This paper (see abstract below) merely exemplifies both the peroneals and FAI as well as AMI.

Take home message?

Keep the peroneals strong with lots of balance work!                                                             

2009 May;37(5):982-8. doi: 10.1177/0363546508330147. Epub 2009 Mar 6.

Peroneal activation deficits in persons with functional ankle instability.

Palmieri-Smith RM, Hopkins JT, Brown TN.

Source

School of Kinesiology, University of Michigan, 401 Washtenaw Avenue, Ann Arbor, MI 48109, USA. riannp@umich.edu

Abstract

BACKGROUND:

Functional ankle instability (FAI) may be prevalent in as many as 40% of patients after acute lateral ankle sprain. Altered afference resulting from damaged mechanoreceptors after an ankle sprain may lead to reflex inhibition of surrounding joint musculature. This activation deficit, referred to as arthrogenic muscle inhibition (AMI), may be the underlying cause of FAI. Incomplete activation could prevent adequate control of the ankle joint, leading to repeated episodes of instability.

HYPOTHESIS:

Arthrogenic muscle inhibition is present in the peroneal musculature of functionally unstable ankles and is related to dynamic peroneal muscle activity.

RESULTS:

The FAI patients had larger peroneal H:M ratios in their nonpathological ankle (0.399 +/- 0.185) than in their pathological ankle (0.323 +/- 0.161) (P = .036), while no differences were noted between the ankles of the controls (0.442 +/- 0.176 and 0.425 +/- 0.180). The FAI patients also exhibited lower EMG after inversion perturbation in their pathological ankle (1.7 +/- 1.3) than in their uninjured ankle (EMG, 3.3 +/- 3.1) (P < .001), while no differences between legs were noted for controls (P > .05). No significant relationship was found between the peroneal H:M ratio and peroneal EMG (P > .05).

CONCLUSION:

Arthrogenic muscle inhibition is present in the peroneal musculature of persons with FAI but is not related to dynamic muscle activation as measured by peroneal EMG amplitude. Reversing AMI may not assist in protecting the ankle from further episodes of instability; however dynamic muscle activation (as measured by peroneal EMG amplitude) should be restored to maximize ankle stabilization. Dynamic peroneal activity is impaired in functionally unstable ankles, which may contribute to recurrent joint instability and may leave the ankle vulnerable to injurious loads.

The EHB....In all its glory...

The extensor hallucis brevis : An overlooked "miracle worker"

The Extensor Hallicus Brevis, or EHB as we fondly call it is an important muscle for descending the distal aspect of the 1st ray complex (1st metatarsal and medial cunieform) as well as extending the 1st metatarsophalangeal joint. It is in part responsible for affixing the medial tripod of the foot to the ground.  Its motion is generally triplanar, with the position being 45 degrees from the saggital (midline) plane and 45 degrees from the frontal (coronal) plane, angled medially, which places it almost parallel with the transverse plane. With pronation, it is believed to favor adduction (1).

It arises from the anterior calcaneus and inserts on the dorsal aspect of the proximal phalynx. It is that quarter dollar sized fleshy protruding, mass on the lateral aspect of the dorsal foot.  The EHB is the upper part of that mass. It is innervated by the lateral portion of one of the terminal branches of the deep peronel nerve (S1, S2), which happens to be the same as the extensor digitorum brevis (EDB), which is why some sources believe it is actually the medial part of that muscle. It appears to fire from loading response to nearly toe off, just like the EDB; another reason it may phylogenetically represent an extension of the same muscle (2-4).

Because the tendon travels behind the axis of rotation of the 1st metatarsal phalangeal joint, in addition to providing extension of the proximal phalynx of the hallux (as seen in the child above), it can also provide a downward moment on the distal 1st metatarsal (when properly coupled to and temporally sequenced with the flexor hallicus brevis and longus), assisting in formation of the foot tripod we have all come to love (the head of the 1st met, the head of the 5th met and the calcaneus).

Why is this so important?

The central axis of a joint (sometimes called the instantaneous axis of motion) is the center of movement of that articulation. It is the location where the motion will occur around, much like the center of a wheel, where the axle attaches. In an articulation, it usually involves one bone moving around another. Lets look at an example with a door hinge.

A hinge is similar to a joint, in that it has parts with is joining together (the door and the jamb), with a “joint” in between, The axis of rotation of the hinge is at the pivot rod. When the door, hinge and jamb are all aligned, it functions smoothly. Now imagine that the hinge was attached to the jamb 1/4” off center. What would happen? The hinge would bind and the door would not operate smoothly.

Now let’s think about the 1st metatarsal phalangeal joint. It exists between the head of the 1st metatarsal and the proximal part of the proximal part of the proximal phalanyx. Normally, because the head of the 1st metatarsal is larger than the heads of the lesser ones, the center of the joint is higher (actually,almost 2X as high; 8mm as opposed to 15mm). We also remember that the 1st metatarsal is usually shorter then the 2nd, meaning during a gait cycle, it bears the brunt of the weight and hits the ground earlier than the head of the 2nd.

The head of the 1st metatarsal should slide (or should we say glide?) posteriorly on the sesamoids during dorsiflexion of the hallux at pre swing (toe off). It is able to do this because of the descent of the head of the 1st metatarsal, which causes a dorsal posterior shift of the axis of rotation of the joint. We remember that the head of the 1st descends through the conjoined efforts of supination and the coordinated efforts of the peroneus longus, extensor hallucis brevis, extensor hallucis longus, dorsal and plantar interossei and flexor hallucis brevis (which nicely moves the sesamoids and keeps the process going smoothly)(1, 5).

Suffice it to say, if things go awry, the axis does not shift, the sesamoids do not move, and the phalanyx crashes into the 1st metatarsal, causing pain and if it continues, a nice spur you can write home about!

Treating and needling this muscle is easy, as it is very accessible on the dorsum of the foot and due to the decreased receptor density, is not too uncomfortable. We like to needle the peroneus longus and short flexors as well, as they all have the function of lowering the head of the 1st ray. Check it out in this quick how to video.

1. Michaud T: Human Locomotion: The Conservative Management of Gait Related DisordersNewton Biomechanics; First Edition 2011

2. https://www.physio-pedia.com/Extensor_Hallucis_brevis

3. http://www.wheelessonline.com/ortho/extensor_hallucis_brevis

4. Becerro de Bengoa Vallejo R., Losa Iglesias M.E., Jules K.T.  Tendon Insertion at the Base of the Proximal Phalanx of the Hallux: Surgical Implications (2012)  Journal of Foot and Ankle Surgery,  51  (6) , pp. 729-733.

5. Zelik, K.E., La Scaleia, V., Ivanenko, Y.P. et al. Eur J Appl Physiol (2015) 115: 691. https://doi.org/10.1007/s00421-014-3056-x

Pain on the outside of the leg? Could it be your orthotic? What you wear on your feet amplifies the effect of the orthotic.

This woman presented with right-sided pain on the outside of her leg after hiking approximately an hour. She noticed a prominence of the arch in her right orthotic. She hikes in a rigid Asolo boot ( see below). Remember that footwear amplifies the effect of an orthotic!

In the pictures below you can see the prominent arch. The orthotic has her “over corrected” so that she toes off in varus on that side. The rigid footwear makes the problem worse. The peroneus group is working hard (Especially the peroneus longus)  to try and get the first Ray down to the ground.

The “fix” was to soften the arch of the orthotic and grind some material out. Look at the pictures where the pen is pointing to see how some of the midsole material was taken out. Notice how I ground it somewhat medial to further soften the arch.

She felt better much better after this change and is now a “happy hiker” :-)

One way to correct an dysfunctional Extensor Hallucis Brevis

The Extensor Hallicus Brevis, or EHB  (beautifully pictured above causing the  extension (dorsiflexion) of the proximal big to is an important muscle for descending the distal aspect of the 1st ray complex (1st metatarsal and medial cunieform) as well as extending the 1st metatarsophalangeal joint.

Since this muscle is frequently dysfunctional, and is one of THE muscles than can lower the head of the 1st metatarsal, along with the peroneus longus and most likely the tibialis posterior (through its attachment to the 1st or medial cunieform), needling can often assist in normalizing function and works especially well, when coupled with an appropriate rehab program. Here is one way to needle it effectively. 

Thoughts on the adductor grouping to ponder. 

I found this while prepping for the dry needling course I am teaching this weekend and thought you may enjoy it. Though the primary actions of the addcutors are well established, secondary actions (whether they are acually internal or external rotators) remains to be elucidated.

Here is a nice abstract that supports the dynamic function of them as external rotators (eccentrically) during gait.

“Anatomical texts agree on most muscle actions, with a notable exception being the action of the adductors of the hip in the transverse plane. Some texts list an action of the adductor brevis (AB), adductor longus (AL), and/or adductor magnus (AM) as internal rotation, whereas others list an action of external rotation. The purpose of this article is to present a functional model in support of the action of external rotation. Transverse plane motion of the femur at the hip during normal gait is driven by subtalar joint motion during the loading response, terminal stance, and preswing phases. During the loading response, the subtalar joint pronates, and the talus adducts. This talar adduction results in the lower leg, and subsequently the femur, internally rotating. During terminal stance and preswing, the opposite occurs; the subtalar joint supinates as the talus abducts in response to forces generated from the lower extremity and in the forefoot. Electromyographic (EMG) studies indicate varied activity in the AB, AL, and AM during the loading response, terminal stance, and preswing phases of the gait cycle. A careful analysis of EMG activity and kinematics during gait suggests that, in the transverse plane, the adductors may be eccentrically controlling internal rotation of the femur at the hip during the loading response, rather than the previously reported role as concentric internal rotators. In addition, these muscles may also concentrically produce external rotation of the femur at the hip during terminal stance and preswing. Physical therapists should consider this important function of the hip adductors during gait when evaluating a patient and designing an intervention program. Anatomical texts should consider listing the concentric action of external rotation of the femur at the hip as one action of the AB, AL, and AM, particularly when starting from the anatomic position.”

Leighton RD. A functional model to describe the action of the adductor muscles at the hip in the transverse plane.Physiother Theory Pract. 2006 Nov;22(5):251-62.Leighton RD. A functional model to describe the action of the adductor muscles at the hip in the transverse plane.Physiother Theory Pract. 2006 Nov;22(5):251-62.

Thinking on your feet. You have less than 20 minutes with this gentleman, as he has to leave to catch a plane. See how you did. 

Lateral foot pain and cowboy boots?

A 55 YO male patient presents with pain in his left foot area of the cuboid and tail of the fifth metatarsal.  He was told that he had a “locked cuboid” on this side by his chiropractor, who provided some treatment and temporary relief. There has been  no history of trauma and Most recently, he has been wearing cowboy boots and doing “a lot of walking” particularly when he was over in Europe and feels this was a precipitating factor.

Watching him walk in his cowboy boots, the rear foot and heel plate of the cowboy boot is worn into varus. Gait evaluation reveals his left foot to remain in supination (and thus in varus) throughout the entire gait cycle. 

Examination of the foot revealed loss of long axis extension at the metatarsophalangeal and interphalangeal articulations. The cuboid appeared to be moving appropriately. (to see why cuboid function is integral, see this post here. ) There was weakness in the peroneus brevis and peroneus longus musculature with reactive trigger points in the belly of each.  There is tenderness over the tail of the fifth metatarsal and the groove where the peroneal muscle travels through as well as in the peroneal tendon as it travels through here. 

So, what’s up?

This patient has peroneal tendonitis at the point around the foot as it goes around the tail of the fifth metatarsal. Discomfort is dull and achy in this area.  The cowboy boot is putting his foot in some degree of supination (plantar flexion, inversion adduction); this combined with the rear foot varus (from wear on the heel) is creating excessive load on the peroneus longus, which is trying to descend the 1st ray and create a stable medial tripod. Look at the pictures above and check out this post here. 

What did we do?

Temporarily, we created a valgus post on an insole for him.  This will push him onto his 1st metatarsal as he goes through  midstance into termiinal stance. He was asked to discontinue using the boot until we could get the heel resoled with a very slight valgus cant. We also treated with neuromuscular acupuncture over the peroneal group (GB 34, GB 35, GB 36 and a few Ashi points between GB34 and 35) circle the Dragon about the tail of fifth metatarsal, GB41 as well as the insertion of peroneus onto the base of the first metatarsal (approximately SP4).   We K-taped the peroneus longus to facilitate function of peroneus longus.  He was given peroneus longus (plantarflexion and eversion) and peroneus brevis (dorsiflexion and eversion) theraband exercises. 

How did you do? Easy peasy, right? If they were all only this straight forward….

The Gait Guys. teaching you to think on your feet and increasing your gait literacy with each and every post. 

The case of the dropped (plantarflexed) metatarsal head. Or, “How metatarsalgia can happen”.

This gentleman came in with fore foot pain (3rd metatarsal head specifically), worse in the AM upon awakening, with first weight bearing that would improve somewhat during the day, but would again get worse at the end of the day and with increased activity. The began insidiously a few months ago (like so many problems do) and is getting progressively worse.

Rest and ice offer mild respite, as does ibuprofen. You can see his foot above. please note the “dropped” 3rd metatarsal head (or as we prefer to more accurately say, “plantarflexed 3rd metatarsal head”) and puffiness and prominence in that area on the plantar surface of the foot. 

To fully appreciate what is going on, we need to look at the anatomy of the short flexors of the foot. 

The flexor digitorum brevis (FDB) is innervated by the medial plantar nerve and arises from the medial aspect of the calcaneal tuberosity, the plantar aponeurosis (ie: plantar fascia) and the areas bewteen the plantar muscles. It travels distally, splitting at the metatarsal phalangeal articulation (this allows the long flexors to travel forward and insert on the distal phalanges); the ends come together to divide yet another time (see detail in picture above, yes, we are aware it is the hand, but the tendon structure in the foot is remarkably similar)) and each of the 2 portions of that tendon insert onto the middle of the middle phalanyx (1) 

As a result, in conjunction with the lumbricals, the FDB is a flexor of the metatarsal phalangeal joint, and proximal interphalangeal joint (although this second action is difficult to isolate. try it and you will see what we mean). In addition, it moves the axis of rotation of the metatasal phalangeal joint dorsally, to counter act the function of the long flexors, which, when tight or overactive, have a tendency to drive this articulation anteriorly (much like the function of the extensor hallucis brevis above in the drawing from Dr Michauds book, yes, we are aware this is a picture of the 1st MTP).

Can you see the subtle extension of the metatarsal phalangeal joint and flexion of the proximal interphalangeal joint in the picture?

We know that the FDB contracts faster than the other intrinsic muscles (2), playing a tole in postural stability (3) and that the flexors temporally should contract earlier than the extensors (4), assumedly to move this joint axis posteriorly and allow proper joint centration. When this DOES NOT occur, especially if there is a concomitant loss of ankle rocker, the metatarsal heads are driven into the ground (plantarflexion), causing irritation and pain. Metatarsalgia is born….

So what is the fix? Getting the FDB back on line for one. 

• How about the toe waving exercise? 
• How about the lift spread reach exercise? 
• How about retraining ankle rocker and improving hip extension?
• How about an orthotic with a metatarsal pad in the short term? 
• How about some inflammation reducing modalities, like ice and pulsed ultrasound. Maybe some herbal or enzymatic anti inflammatories?

The Gait Guys. Increasing your gait and foot literacy with each and every post. 

1. http://en.wikipedia.org/wiki/Flexor_digitorum_brevis_muscle

2. Tosovic D¹, Ghebremedhin E, Glen C, Gorelick M, Mark Brown J.The architecture and contraction time of intrinsic foot muscles.J Electromyogr Kinesiol. 2012 Dec;22(6):930-8. doi: 10.1016/j.jelekin.2012.05.002. Epub 2012 Jun 27.

3.Okai LA¹, Kohn AF. Quantifying the Contributions of a Flexor Digitorum Brevis Muscle on Postural Stability.Motor Control. 2014 Jul 15. [Epub ahead of print]

4. Zelik KE¹, La Scaleia V, Ivanenko YP, Lacquaniti F.Coordination of intrinsic and extrinsic foot muscles during walking.Eur J Appl Physiol. 2014 Nov 25. [Epub ahead of print]