“If you screw-up toe-off, the rest of the movement is compensation.”
—The Gait Guys
Just when you thought the running gods had grown tired of tormenting us with new and ever more exasperating running injuries, I’m saddened to report they’re still at it and as sadistic as ever. This latest one— functional hallux limitus (FHL)—which, like all the other injuries, has a flashy Latin name, translates to “this really sucks” . . . well, not to that exactly, but if you’ve got it, it certainly does. That you’ve likely never heard of FHL isn’t a surprise; few have. That’s because FHL—a pint-sized affliction with big consequences for runners— keeps a low profile, literally and figuratively.
For something so ruinous, FHL doesn’t make its entrance with the drama of a sprained ankle or torn hamstring. Instead it infiltrates our body with a Ninja’s stealth, then conceals itself in the most inconspicuous of places: the big toe joint. From there, FHL sows the seeds of dysfunction throughout the body by creating the illusion that the joint operates perfectly, even as its mobility is seriously compromised. FHL’s deception leaves its victims oblivious and clinicians flummoxed, making it one of the most insidious, least-known, and shockingly underdiagnosed conditions in running.
Before venturing further into this dark place, it’s important to know what we’re dealing with, so I’ve parsed FHL’s three components:
functional—using something (in this case, our body, and more specifically the big toe and foot) to do something weight-bearing (running)
hallux—the medical/scientific/Latin name for the big toe
limitus—limited; in this case, referring to the big toe joint’s limited bendability
Translation complete, we now understand that FHL is a condition occurring only when the foot is used for its designed purpose: locomotion (and as a consequence of locomotion, bearing weight). It’s as a result of weight bearing that the big toe’s bendability becomes limited to 30 degrees, usually less. Capiche?
FHL’s Deception Revealed: The Left Image Shows the Hallux Bending Nicely with the Foot Unloaded; The Right Image Shows a Thumb Applying Load Under the First Metatarsal Head and the Hallux’s Range of Motion Disappearing Almost Completely
You should also know that there are two other, much worse conditions that are part of the hallux trilogy which I won’t talk about because they’re just too damned depressing, but I’ll give them a brief mention anyway. They are structural hallux limitus, where the mobility of the hallux is disrupted during both weight-bearing and non-weight-bearing activities, and the ultra-nasty hallux rigidus, where an unbendable big toe is accompanied by significant degeneration of the big toe joint. These baddies can substantially disrupt, even end, your running.
In a nutshell, what happens to those hapless souls who cross paths with FHL is that the big toe joint, known to those in the trade as the metatarsophalangeal joint (in short MTP joint or sometimes MPJ), loses its bendability when the foot is weight bearing. The more dynamic the type of locomotion we’re engaged in—for us it’s running, which is very dynamic—the more important a mobile MTP joint is. As mentioned, it must bend, or dorsiflex, a bare minimum of 30 degrees, but ideally between 65 and 75 degrees, as we run to ensure a proper and powerful toe-off. I define a proper toe-off as a high heel with the sole of the foot close to, or at, vertical, and the heel neither abducting or adducting (tipping in or tipping out). Check out these guys . . .
Finland’s Pekka Vasala and Kenya’s Kip Keino Display Awesome Form – With Perfect Toe-Off – In the 1972 Olympic 1500 Metre Final. Whether We’re Olympians or Casual Runners, Hallux Range of Motion Plays a Huge Role in Our Ability to Run Fast and Pain Free
Most runners with FHL are aware of blocked movement and pain in their MTP joint, so they use a simple and somewhat effective strategy to deal with it: they lessen the bending of the joint by moving around the restriction. And voilà, the pain is gone . . . or reduced. Brilliant, no? At first it is, but in the long run it’s terrible. Why’s that? Because as clever as runners think they are, they’re oblivious to the mayhem compensations like this can create.
Assuming that all our bodily systems are in perfect working order (that’s a really big assumption, but I won’t address the many variables now), here’s a very simple way of looking at how the body gets things done: think of your body as a home computer, consisting of two essential components, the operating system (OS) and the hardware (the physical parts of the computer). Your nervous system is the OS; your body (in this case, your musculoskeletal system) is the hardware. When given orders from the nervous system, the musculoskeletal system (the bones, skeletal muscles, fascia, ligaments and tendons) has one goal: task completion. It doesn’t think about movement economy or efficiency, or about the implications of lifting heavy things with bad form. The orders sent by the nervous system to the musculoskeletal system are starkly unambiguous: it doesn’t have to be pretty, just get the job done.
And movement for many isn’t pretty: if we’re dealing with injuries, pain, advanced age, poor body awareness, excess weight, or an array of pathologies/diseases (take your pick), the way we’ll move might be downright ugly. It’s against this backdrop that the musculoskeletal system “gets the job done” by moving in a way that’s not only unhealthy, but which perpetuates continued poor movement by grooving an aberrant pattern in the nervous system. And once that pattern has been established, it’s damned hard to correct.
Compensation—automatically shifting movement/load away from the “natural” or “best” path for a particular movement to an alternate route—begins a process of musculoskeletal overload, eventually leading to syndromes and inefficiencies, imbalances and pain. Is it really that bad? Yes, it usually is. Compounding the problem is that we’re usually not even aware we’re compensating; the body simply defaults to a path that’s free of restriction or pain. Even if we know we’re compensating, we’re probably okay with it simply because it allows us to run, or move, unencumbered, or at least with less pain.
One consequence of FHL, gluteal amnesia, shows how a particular structure (in this case, the gluteus maximus muscles) far from the source of the problem (the MTP joint) can be adversely affected. Gluteal amnesia occurs when an immobile MTP joint prevents full hip extension in late mid-stance, otherwise known as the hip extension phase of gait. Because the gluteus maximus is the primary extender of the hip, it won’t contract properly when hip extension is compromised, and as a result becomes partially deactivated and weaker. It then is less effective at doing its job, which is to extend, abduct and externally rotate the hip/leg when we run.
Another problem associated with FHL is a low gear push-off. When the bendability of the MTP joint is comprised during gait, the foot will move around the block and the heel, in turn, will abduct (tip to the outside). Because of this, the plantar fascia can’t tension or load energy (an essential step for loading strain energy by tensioning the plantar fascia is known as the windlass mechanism), and the propulsive force that must happen with toe-off is lost, hence the term “low-gear push-off.”
The million-dollar question is, of course, how does a person get FHL? Without question, certain foot types are at risk for FHL, the over-pronated foot in particular, but the current thinking on its cause(s) is not definitive. As is often the case, conditions or pathologies like FHL manifest when an inherited predisposition meets the right circumstances, commonly known as the interaction of nature and nurture. The website of the Mayo Clinic (mayoclinic.org) notes that “wearing tight, narrow shoes might cause bunions or make them worse” and, in the next sentence, that “bunions also can develop as a result of an inherited structural defect.” Others assert that FHL is entirely self-inflicted, created by the habitual use of toe-constricting footwear.
For those hoping to avoid the horrors of MTP joint dysfunction, here are some recommendations:
1. All footwear (this means anything you put on your feet) must have a wide toe box—no exceptions.
2. Go barefoot whenever possible.
3. Use toe spacers.
Toe Spacers Can Help Reverse the Inward Migration of the Big Toe (Hallux Valgus)
4. Do lots of yoga, with postures that focus on mobilizing the ankles and big toe joints.
A Great Posture for Mobilizing Our Feet, the Big Toe in Particular
As a yoga teacher, movement coach, and runner, I see the consequences of limited or rigid halluces (“ha loo sees”: more than one hallux) every day: bunions, bouncy strides when walking or running, an inward migration or abduction, of the big toe toward the second toe, and unexplained pain in the knee, hip or low back.
FHL is frequently overlooked by health care professionals as a cause of dysfunction and pain elsewhere in the body. Those who should catch FHL are medical doctors with training in orthopedics or sports medicine, as well as doctors of chiropractic and podiatry, and physical therapists, all of whom possess an excellent understanding of the musculoskeletal system and the consequences of limited mobility in the MTP joint.
An important final point (and repeating what I mentioned earlier): the test for FHL is dynamic, meaning the foot must be in a fully weight-bearing, closed kinetic chain position when the MTP joint is assessed. Remember, the name for this condition is functional hallux limitus; it appears only when the foot is functioning, not when you’re kickin’ back and the foot’s propped up on an ottoman. Clinicians, if they consider the big toe at all, miss FHL because their assessment is passive, not dynamic. If the leg is supported and your friend bends your big toe back 80 degrees without pain or restriction, that’s great, but it only means you don’t have either of the two more severe manifestations of the hallux trilogy. You can, however, still have FHL.
I’d be interested in hearing from readers about your experiences with FHL, structural hallux limitus, or hallux rigidus and how it affects your running. Send your story to firstname.lastname@example.org