Metatarsalgia and Morton's Neuroma
This article will explore two conditions of the forefoot which can affect runners. Metatarsalgia is an inflammatory condition of the metatarsal heads of the foot while Morton's Neuroma is a fibrosis around the neurovascular bundle of the nerves that supply the toes. Both cause pain in the forefoot region, but they have different clinical presentations. NOTE - Some authors argue that Metatarsalgia should refer specifically to forefoot pain due to abnormal biomechanics of the foot, while others suggest that the term be used to lump together any and all conditions of the forefoot, which would include Morton's Neuroma. For our purposes, we will focus primarily on the definitions I outlined above.
The foot is designed a lot like your hand. If you look at your hand, the toes (Phalanges) would be represented by the fingers. The next row of bones in the foot are called the metatarsals and they are equivalent to metacarpals in the hand. Where the toes (phanlanges) meet the metatarsals, we have a joint. This joint is a lot like the knuckle on your hand. Make a fist with your hand and you'll have a good idea what I'm talking about. In-between the bones of the foot we have the nerves that reach all the way to the toes (see below).
|Now, with Metatarsalgia, you get a
bruised feeling in the ball of the foot. The pain is usually located right about
where a 'knuckle' of the foot would be located, on the underside of the foot but it may
also radiate over the foot and sometimes up the calf.
Neuroma, on the other hand, typically presents as
pain or numbness on the bottom of the middle -to-outside of the forefoot which often
radiates into the 3rd and 4th toe. This area is outlined in the diagram at the
right. The pain can be burning, sharp and agonizing, intermittent or constant.
A Neuroma is a swelling in a nerve caused by the laying down of fibrous tissue in response
to long-standing irritation. Neuroma formation is attributable to compression of
the interdigital (between the toe) nerve against the intermetatarsophalengeal bursa.
Mechanism of Injury - Metatarsalgia
Metatarsalgia is most often a result of faulty distribution of weight on the forefoot. Normally when walking, weight is transferred from the heel to the outside of the foot and then we finish with the weight on the inside as we 'toe-off' at the end of each step. During toe-off, most of the weight is carried by the big toe. When standing, the first metatarsal (at the big toe) caries 2/6 of the body weight and each of the others carries 1/6. If increased weight is habitually carried on the lateral (outer) metatarsals, this can cause microtrauma in the joint capsule and around the head of that particular metatarsal and thereby lead to injury.
Normally, the little muscles that run between the bones of the feet contract during the final phase of each step to prevent the forefoot from splaying (widening) and the toes from curling. If these little intrinsic muscles don't do their job, the forefoot spreads and the toes curl which causes the metatarsal heads to be forced down and they contact the ground harder and this can lead to injury.
As you can probably guess, onset is usually gradual as microtrauma takes a while to add up into an injury. However, it may arise suddenly if there is trauma to the area or if new shoes are involved. Sudden trauma might include landing hard on the ball of the foot while barefoot or while wearing non-cushioned shoes or stepping on a stone while running.
What To Do About Metatarsalgia
Most cases should respond to conservative care. In fact, many times all that is needed is some home treatment. First, start with ice on the ball of the foot. This will help to decrease the inflammation in the joint. Second, make sure your shoes aren't worn out and that they are the correct type of shoe for your foot. If you pronate excessively, you will need a good motion control shoe. If you are replacing your shoes, consider a pair that offer some form of forefoot cushioning. That has worked wonders for me in the past, as I have had to deal with Metatarsalgia on occasion. If you wear high heels, quit! All that extra force on the ball of your foot may be at the root of the problem.
Next you might want to try creating a little forefoot pad for yourself that will help protect the metatarsals. It doesn't take much padding to notice a difference. I recommend buying some 'moleskin' which is a thick adhesive type bandage that people use to prevent blisters. Cut a circle about the size of a quarter or a bit larger (an inch across, roughly) and stick that to your forefoot in the middle of the ball of your foot. It doesn't have to be where the sore 'knuckle' sits - we're just trying to build that arch up a bit. Then take a slightly larger piece of moleskin, cut into a circle, and stick it over top so you'll have a double layer. That should be lots to build up the metatarsal arch. Try wearing that around for a couple days and see if it improves things. If so, continue for a week or two before trying to go without.
It may be necessary to look into orthotics to correct a biomechanical problem of the foot. There are some orthotics on the market such as the 'Viscoped' by "Bauerfeind" that are made out of silicone and they offer excellent cushioning. One model even has a metatarsal arch built into which I have worn with great success.
Mechanism of Injury - Morton's Neuroma
The most common mechanism of injury is due to repetitive trauma - i.e. - chronic irritation. This causes the ends of the nerves to get trapped and pinched between the metatarsal heads during the push-off phase of walking. If one's foot pronates excessively during the push-off phase, this may produce metatarsal 'shear' whereby the bones pinch and rub the nerve to the point where it develops a Neuroma. Also, hammer or claw toes can cause a stretching of the interdigital nerves which causes it rub on the ligaments, thereby creating a Neuroma. Acute onset, such as stepping on a sharp object or falling on the ball of the foot, is also possible.
Signs and Symptoms - Morton's Neuroma
What To Do About Morton's Neuroma
Treatment can be either conservative or surgical. Daily cold whirlpool and ultrasound can help decrease inflammation and pain. It is important to have the mechanics of the feet addressed and any lack of movement in the joints of the foot should be addressed and corrected. A metatarsal pad, placed on the heel-side of metatarsal heads, can often alleviate the pain. Orthotics can also be helpful. Surgical treatment is carried out when conservative measures fail and involves resection of the enlarged section of the nerve.
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