quadratus plantae


Is your 5th toe curled under ? What do you do when “this little piggy” can’t go wee wee wee all the way home.

Have a look at the 4 photos above.  You will see this curling of the lesser toes quite often in your practice, and when you know what it means it can help to guide your thinking, both from a diagnostic and treatment perspective.  

You should have noticed in the photos that the 4th and 5th toes curl under and are hyper-flexed, and this is at rest.  So, what does this mean ?

It means that the long flexors are overactive, the extensors are underactive, and the adduction pull of the long flexors is unopposed by the under appreciated quadratus plantae muscle.

Look at the clinical drawing. The quadratus plantae has 2 heads, a medial head and a lateral head.  Being able to clinically test these two heads will give you much insight into the function of the foot and when you see these outer two toes curling under, as you see in the photo, you will always see weakness of the lateral head of the quadratus plantae.  

The quadratus plantae arises from two heads separated from each other by the long plantar ligament. The medial head is larger and more muscular, attached to the medial calcaneus;  the lateral head is smaller and more tendinous, attaching to the lateral border of the inferior surface of the calcaneus and the long plantar ligament.  The two portions join and end in a flattened band which inserts into the lateral, upper and under surfaces of the tendons of the flexor digitorum longus, usually the second, third, and fourth toes.

But this time, if you have studied the drawing, you should notice the oblique line of pull of the long flexors.  This should in fact create this undesirable curling effect of the lateral two toes since they are so far out on the oblique line of pull. However, if you look at the insertion of the lateral head of the quadratus plantae you should be able to conclude that this head is designed to offset this oblique pull of the outer two long flexor tendons.  The quadratus creates a posterior pull on the outer long flexor tendons ensuring that the curling effect (as seen in the photo) is nullified. Thus, we have a clinical presentation of a weak lateral head of the quadratus plantae (and probably a few others which we will not discuss here so as to not dilute the purpose of today’s post). Now you just have to figure out why it is weak or if there is a biomechanical reason for its insufficiency

  • is there a foot type presenting itself that makes it difficult for this muscle to create sufficient posterior pull to offset the tremendous leverage of the long flexors? Maybe a forefoot varus, which gives the flexor tendons a mechanical advantage or a forefoot valgus which puts the quadratus plantae at a mechanical disadvantage? (Taking our National Shoe Fit Certification Program will help you get closer to understanding many of these issues.)
  • Are their other anatomical variants like an increased forefoot width or bunions (medial or tailor’s)
  • is there excessive rear or midfoot pronation?
  • Shoe choice problem ?

Some folks do have adequate function of the quadratus plantae. Note the lovely feet in the last picture … .  they must have strong lateral quadratus plantae and abductors of the lateral foot and toes ! And, they have great toe separation, thus great intrinsic interossei muscles, and nice flat toes (great balance between flexors and extensors).

So, what do you do?

  • you could do a surgery, amputate or fuse some of the joints to make them look better. Extreme for a problem like this
  • you could ignore the issue and hope it goes away. (in all likelihood it will worsen)
  • you could give them long flexor, toe scrunching Towel-curling, marble-grasping exercises , like you see all over the internet…and give the flexor digitorum longus even more of a mechanical advantage, and make the problem worse
  • you could give them exercises to increase the function of the long extensors, which would increase the mechanical advantage of the quadratus plantae. like the shuffle walk; lift, spread and reach and tripod standing exercises (hmm…sounding better)
  • be a real clinician and in addition to looking at the foot, look north of the foot to see what might be causing the problem (loss of ankle rocker, insufficient gluteal activity, loss of internal rotation of the hip, etc) Hmmm; sounding like a good idea too…

The Gait Guys. Hammering it home, day after day, about the importance of gait and giving you clues to be a better _________ (insert athlete, coach, trainer, clinician, shoe fitter, rehab specialist…).

Toe sardines. What have we done to our feet ?

Note that form follows function. If you are observant, you will see the deformation of the 5 digit, just like in this case as the quadratus weakens and the long flexors dominate. The toe begins to spin laterally, and thus the plantar toe pad begins to deform medially, look closely, you can see that here in the video.

Does this look like your foot ? There are a few subtle issues here. 

In the foot, the toe that delineates abduction and adduction of the toes is the 2nd toe. The 2nd toe is considered the anatomic middle of the digits and forefoot. Any toe or movement that moves away from the 2nd toe is abduction and any movement towards the 2nd toe is adduction. This is obviously different than in the hand where the 3rd digit, the one you use during road rage, is the reference digit. Next time you are questioned, tell them you threw them your reference finger, not “the bird”, it is a more accurate descriptor.

In this foot, note how neatly and tightly packed the cute little toes are, all snuggled up to their brothers and sisters. Remember, form follows function. Obviously function has been low on these fellas, at least in abduction.  This often comes from snug toe box footwear and lack of abduction (toe spread) use.  But make no mistake, this is a weak foot.

Today we wish to really focus your attention to an old topic, just a revisit. We can see the 4th and 5th toes curl under from the probably weak lateral head of the quadratus plantae thus encouraging unopposed oblique pull of the long flexors of the digits (FDL). See this post here for an explanation of this phenomenon.  There is also obvious imbalance between the long and short flexors and extensors in these toes, the long flexors are expressing more tone, and that means the long extensors are deprived. 

Note that form follows function. If you are observant, you will see the deformation of the 5 digit, just like in this case as the quadratus weakens and the long flexors dominate. The toe begins to spin laterally, and thus the plantar toe pad begins to deform medially, look closely, you can see that here in the video. This spin can carry the toe nail so far laterally sometimes that the nail can begin to touch the ground during gait and cause painful nail lifting with even some losing the nail. 

There is plenty of life left in this foot, but you have to get to it quickly and get them in lower heeled shoes if tolerable and ones with a wider toe box.  The client needs to be retaught how to access the toe extensors and abductors. Lumbrical retraining, which is a recurrent topic here on our blog, should also be instituted. 

Shawn Allen, one of the gait guys