Why Metatarsalgia May Not Be What It Seems
- William Fishco DPM FACFAS
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I want to dedicate this blog to facilitate a better understanding of metatarsalgia. If you think of the top 10 problems that you see on a daily basis, “ball pain” is probably somewhere on that list. So when you walk into the treatment room with a new patient and your medical assistant says the patient is complaining of pain in the ball of the foot, what are you thinking? Maybe it is simply a dermatological problem such as a callus or wart. Maybe it is a Morton’s neuroma or a metatarsophalangeal joint (MPJ) problem such as capsulitis/bursitis.
Let us assume there are no skin lesions on the ball of the foot so we can focus on trying to break down the key elements of the history and physical exam. When the patient is describing symptoms, you should listen for important descriptors such as numbness, tingling, swelling, toe stiffness, fullness on the ball of the foot or that it feels like walking on a lump or stone bruise.
You may ask questions such as whether pain radiates to a particular toe(s) and aggravating factors such as activity, shoe gear, barefoot walking, etc. You also want to confirm that there is no pain on the dorsal foot, which would of course immediately change your impression of the clinical condition.
I will now focus on the subjective complaints of numbness and tingling. We all know that burning, tingling and numbness are neurological symptoms. If your patient tells you there is burning or numbness on the ball of the foot, what does that mean? Does that mean the patient probably has a Morton’s neuroma? Out of all of the subjective symptoms, I place the least amount of emphasis on neurological symptoms in making my initial diagnostic impression. Do not get caught in the trap that numbness to a toe equals neuroma.
Essential Keys To The Physical Exam
Now let us move on the physical examination with the patient who has told you that he has pain in the ball of the foot. It feels like there is a lump under the skin and there is numbness and tingling to the central toes. The first thing I do even before I touch the foot is a quick visual inventory to get an idea of the foot type.
Here is the mental checklist that I go through. Does the patient have a high arch or low arch? Does he have deformities such as hallux valgus? Does the patient have hammertoes? What about the length of the second toe (i.e. Morton’s foot type)?
When it comes to pes cavus, high weightbearing will generally be on the heel and lateral ball of the foot whereas pes valgus feet tend to have higher pressures on the medial ball of the foot. Hallux valgus and hammertoes will have increased pressures to the central ball of the foot. In the Morton’s foot type, increased weightbearing to the second metatarsal head is present.
Once I have an idea of the foot type and potential mechanical influences that may be contributing to the apparent pathology, I begin the physical exam. I have a systematic way of examining the “ball” of the foot. Before I do anything, I tell the patient that I am going to examine the foot and most of the maneuvers that I do will not hurt or cause any discomfort. I will eventually get to the area that is sore. That way the patient will not try to help me by saying “It doesn’t hurt there, it hurts here.”
The first thing I do is the Kelikian push-up test. I want to see the sagittal plane position of each toe, especially the second toe. If the second toe is “riding high” or drifting medially, I will make a mental note of that as it may be indication of MPJ instability. I will move each toe through a range of motion. I start with the great toe, then the fifth toe and work toward the second toe. I know the most common MPJ problem will be the second so I want to examine that last.
I will proceed to examine the intermetatarsal spaces. I will start in the fourth space and work medially to the first. I conduct the interspace exam by putting my thumb plantar and index finger dorsal, taking care to make sure I am palpating the interspace and not too medially or laterally to palpate the joint capsules. After exerting even pressure, I will then add lateral compression with my left hand by squeezing the first and fifth rays together. With this maneuver, I am trying to palpate any clicking in the interspace, which may represent a neuroma or intermetatarsal bursa.
The final maneuver is palpation of the metatarsal heads. I will palpate two areas of each of the lesser metatarsal heads and the plantar plate, which is near the sulcus where the toe meets the foot. I will also palpate more proximally over the metatarsal head. Pain in the region of the plantar plate is consistent with an acute inflammatory condition of capsulitis. I perform range of motion on the lesser toe joints.
If there is any pain, then this is consistent with a joint problem. Neuromas are not painful when you move a toe joint. If this area is painful, I will subsequently perform a Lachman test to determine if the plantar plate is ruptured. This maneuver always occurs bilaterally as the patient may have ligamentous laxity, which may give you a false positive.
Always take X-rays to rule out unusual causes of pain, such as an old Freiberg’s infraction, but most importantly to evaluate for metatarsal length pattern, the metatarsophalangeal joints and associated pathologies such as disorders of the first ray.
Arriving At An Accurate Diagnosis
Now that we have gathered some information, it is time to make a diagnosis.
Scenario #1: neuroma. There is no pain with range of motion of the metatarsophalangeal joints or with palpation of the plantar metatarsal heads. You have successfully ruled out toe joint disorders. Palpation into the third intermetatarsal space is painful and you may or may not feel a click.
Scenario #2: MPJ capsulitis/bursitis. Loading the foot reveals elevation of the second toe in comparison to the remaining lesser toes. There may or may not be a hammertoe deformity of the second toe. There is pain with palpation of the second plantar metatarsal head. Range of motion of the second toe joint is painful, especially with plantarflexion of the toe. Range of motion is fluid-like, not stiff or crunchy, which would be more consistent with an arthritic condition.
There are a number of ways to name the condition of scenario #2. I have heard it called MPJ instability, synovitis, capsulitis, bursitis, arthrosis, predislocation syndrome, plantar plate dysfunction, lesser metatarsal overload and I am sure there are others. In any event, this is purely a disorder of the joint.
It is my personal belief that metatarsalgia is one of the most commonly misdiagnosed problems in the foot. I see too many patients who present to my office with scars in the second interspace or have had alcohol injections into the multiple interspaces. When I examine them, there is a clear-cut case of lesser MPJ pathology.
The impetus to write about this topic came to me last week when I had a patient with a neuroma that required surgery. Just so you know, I may remove about two or three neuromas a year due to the infrequency of presentation and that many do get better with conservative care. Anyway, the anesthesiologist commented as I made the final snip to remove the neuroma from the foot: “Wow, that is a big neuroma and you found it so quickly.”
I asked him what he meant by that and he said there are times when the surgeons he has worked with in the past have been poking around to find the neuroma for a half an hour and not much comes out. I then told him that those are the cases that I refer to as a “no-roma.”
What is the bottom line? In my experience, metatarsalgia is most often caused by second MPJ disorders, not neuromas. Neurological symptoms do not make a diagnosis of neuroma. I have found that numbness and burning are common complaints with MPJ capsulitis/bursitis. Inflammation of the capsule in a very small anatomic space can cause nerve irritation. Removing the nerve will not solve the problem in the long run. Diagnostic injections of lidocaine into the interspace are of little value as all pain surrounding the joint will be eliminated regardless of the causation.
We all know that there are other lesser common causes of metatarsalgia but MPJ disorders and neuromas comprise the majority of cases. I would venture to say that in my practice, a conservative estimate of ratio of MPJ disorders versus neuroma for the cause of metatarsalgia is 30:1.
Hopefully this information will help you develop a more thorough approach to diagnosing the causes of metatarsalgia. After all, we are the experts in diagnosing and treating disorders of the foot and ankle. Unlike primary care physicians (no disrespect intended) who tend to believe heel pain equals plantar fasciitis, ball pain equals neuroma and big toe joint pain equals gout, let us give our patients the thorough evaluation and treatment that they deserve.