Ahh yes, the lumbricals. 

One of our favorite muscles. And here it is in a recent paper! This one is for all you fellow foot geeks : )

Perhaps the FDL (which fires slightly earlier than the FHL) and FHL (which fires slightly later and longer) at loading response, slowing pronation and setting the stage for lumbrical function from midstance to terminal stance/preswing (flexion at the metatarsal phalangeal joint (it would have to be eccentric, if you think about this from a closed chain perspective) and extension (actually compression) of the proximal interphalangeal joints.

“The first lumbrical arose as two muscle bellies from both the tendon of the FDL and the tendinous slip of the FHL in 83.3 %, and as one muscle belly from the tendon of the FDL or the tendinous slip of the FHL in 16.7 %. These two muscle bellies subsequently merged to form the muscle belly of the first lumbrical. The second lumbrical arose from the tendinous slips of the FHL for the second and third toes as well as the tendon of the FDL in all specimens. The third lumbrical arose from the tendinous slips of the FHL for the third and fourth toes in 69.7 %, and the fourth lumbrical arose from the tendinous slip of the FHL for the fourth toe in 18.2 %. Some deep muscle fibers of the fourth lumbrical arose from the tendinous slip of the FHL for the second toe in 4.5 %, for the third toe in 28.8 %, and for the fourth toe in 15.2 %.”

Hur MS1, Kim JH, Gil YC, Kim HJ, Lee KS. New insights into the origin of the lumbrical muscles of the foot: tendinous slip of the flexor hallucis longus muscle. Surg Radiol Anat. 2015 May 12. [Epub ahead of print]

When the Short Toe Extensors Try to Rule the World !

A case of a runner with forefoot pain.

This is a runner of ours, one of the fastest young men in the state of illinois, top 10 in the country in mid-distance, top 20 in the USA in cross country.

He came in with left forefoot plantar pain.  He explained (in a matter of words) that he was having pain at full forefoot loading at heel rise /push off.

We watched him walk, saw this visual problem present itself in dynamic motion (yup, no stop frame video on this one, not when you see it about 10 times a month !) and noted a subtle left lateral hip/pelvis shift past what would be considered normal for frontal plane mechanics.

On the table this is a photo of his feet.  What do you see ?

We see a suspected (which you will try to confirm on examination) increase in short extensor (EDB, extensor digitorum brevis) muscle tone.  Increased long extensor (EDL, extensor dig. longus muscle) tone would have represented itself with the distal toes also extended but here we see a relative dominance of the long flexors (FDL, Flexor dig. longus) with the heightened short flexor increase.

We also see more confirmation of heightened long flexor tone (FDL) by the degree of heavy callus formation on the very tip of the 2nd toe (it was on all 4 lateral toes but the photo is not clear enough to demonstrate).  You can also see supporting evidence of heightened long flexor dominance by the subungual hematoma (bleeding under the 2nd toe nail). (How does this correlate ? Well, in most runners with excessive long flexor tone/use not only do they flex and claw so much in the shoes that the callus is on the tip of the toes but the nail also begins to lift as the  nail is caught on the sock liner of the shoe as the toe flexes, slowly, mile by mile pulling the toe nail from the nail bed thus bleeding underneath it).  Yes, it is NOT from the toes hitting the front end of the shoe !

Our examination confirmed weakness of all lumbrical muscles and of the flexor digitorum brevis and lateral quadratus plantae.  The patient could feel the strength/engagement difference as compared to testing on the right foot of the same muscle groups (we always compare side to side, for us and for the patient’s awareness).  The extensor digitorum brevis muscle mass on the lateral dorsum of the foot was tender as were the tendons along their course.  There was also weakness higher up in the kinetic chain at the lower division of the transversus abdominus and internal abdominal oblique, and frontal plane hip stabilizers (gluteus medius; anterior-middle-and posterior divisions).The 2nd and 3rd metatarsal heads were remarkably tender to palpation and it was obvious that the metatarsal fat pads had migrated distally from the lumbrical muscle weakness.

Sometimes a grasp response by the long flexors can represent a propioceptive /balance deficit during single leg stance phase so be sure to test those centers as well (cerebellar, vision, joint position sense, inner ear-vestibular apparatus). 

So, what is the take away for the non-medical person, the runner next door if you will ?  Lets just say, symmetry wins and when asymmetry is apparent, bring it up to the people that do your body work.  Hopefully, what you and they see will be assessed in a clinical light, and as a team you can get to the bottom of what is not working…….and in this case…..what was causing not only the plantar foot pain, but the left lateral hip sway outside the frontal plane.

———we are, The Gait Guys……Shawn and Ivo

The Quadratus plantae (Flexor accessorius) muscle. Do you have foot pain ?

(*There are two pictures here on the blog. Move your cursor over to the side of the photo and you will see that you can toggle between the photo and anatomy pic).

This is a great, but highly overlooked, muscle.  The QP acts to assist in flexing the 2nd to 5th toes.  Equally important is its effect of offsetting the oblique pull of the long toe flexor group (flexor digitorum longus). It has two heads, medial and lateral.  The medial head is attached to the calcaneus, while the lateral head originates from the lateral border of the calcaneus, in front of the lateral process of the calcaneal tuberosity and the long plantar ligament.

The fact that we just love, and one that we believe is often overlooked is the acute angle at which the muscle heads attach into the tendons of the flexor digitorum longus (see picture) and has a rather dramatic alignment effect on the lateral 3 digits (since the line of pull on the long flexor tendons to these 3 digits is most dramatically changed by the purely posterior pull of the Quadratus Plantae.  As you can see in this stripped down anatomy picture, without the QP pulling on the tendons of the FDL to these 3 lateral toes, those toes will have to curl medially and gently flex (*see the photo, a classic presentation!)  By having a competent and active QP that oblique line of pull of the FDL /long flexors is rearranged to be more of a pure posterior pull and you will not see this classic lateral 3 digit curl and medial drift. This action is accentuated in a cavus foot type, where the pull of the FDL will be accentuated, due to the mechanical advantage afforded it and relative adduction of the forefoot with respect to the rear foot.

In the photo you can see a classic representation of a deficient Quadratus Plantae, in this case the patients lateral head was dramatically weaker than the medial, but both were weak.  So, summary time….if you know your anatomy, know your biomechanics, and if you can test the muscle bundles specifically……..then you can see why form follows function (and in this case, why form has followed dysfunction).  As we always say, “ya gotta know your stuff”, and you have to test what you suspect……there are other things that could also do this……so, let your eyes gain info, let your brain process and prove or disprove the information.

we are…….the gait guys !