Morton's Neuroma
Feelings of pain, numbness, or tingling in the ball of the foot or toes could be due to pressure on a nerve in the foot.
Nerves are the structures in the body responsible for sensation and giving movement commands. Their structure is roughly similar to an electrical wire, with the delicate technical bits that send and receive information covered by a protective sheath.
The nerves that provide sensation, the feelings of hot/cold/pressure/vibration, to our toes travel up along and between the metatarsal bones. These are called the digital nerves because they connect to our digits or toes. There is a decent amount of space for these nerves along the shafts of the metatarsals, the long bones leading to the forefoot, but at the more bulbous heads, where the bones contact the ground, things can get a little tight. Since the ends of the metatarsal bones are thicker than the shafts there is just flat out less space for the nerves to run between them.
The bones of the foot with the metatarsal shafts highlighted in red and the metatarsal heads highlighted in blue.
The bones may also be pushed closer together by pointed toed shoes or shoes that simply aren’t wide enough, further limiting space for the nerves. Shoes with a high heel can also shift weight towards the front of the foot creating additional pressure and lack of space.
When irritated the lining of the nerves may become thicker to help protect the sensitive internal tissue of the nerve. Much like how we develop calluses on our working hands for feet. This thickened tissue does however take up more space, which can cause more irritation, leading to more thickening and so on in an unfortunate feedback loop. This thickening of the nerve sheath referred to generally as a neuroma. Neuroma’s in the forefoot specifically were largely described by a fellow named Thomas George Morton in the 1870s, thus they bear his name.
A pinched nerve, also referred to as an impinged nerve, can lead to feelings such as such as:
- Sharp pain
- Tingling or buzzing
- Numbness
- Hot, cold, or burning
- A sensation like standing on a marble
A pedorthist can check for a Morton’s neuroma by applying pressure to the sides of your forefoot, right at the base of your toes, and seeing if it aggravates any symptoms. It also possible to hear a little ‘click’ as the bones shift around a hardened neuroma. By squeezing in between your toes a pedorthist may also be able to locate the neuroma by touch, feeling it between their fingers.
So, what can we do to help?
Earlier we talked about a metatarsal pads: https://www.barkspedorthics.ca/blog/metatarsalgia
The location of a metatarsal pad under the foot is highlighted in red. The upper surface of the pad is shaped like an arch and the overall pad is teardrop shaped.
These pads can take some pressure off of the ball of the foot, but more specifically in the case of a neuroma we can do something really neat. The top of the curved, like an arch, and therefore it has a high point. If we can line up that high point right between the shafts of the bones one either side of the neuroma when weight is placed on the foot one bone will settle down more in one direction and the other will settle down in the opposite direction. Essentially spreading out the bones as they rest on either side of the high point of the pad. This can provide a lot of relief from the symptoms of a Morton’s neuroma as well as perhaps give the thickened tissue a chance to recede due to their being less irritation.
A cross section of the foot showing the location of a digital nerve in between the metatarsal bones.
A cross section of the foot showing the location of a metatarsal pad that is providing relief to a previously compressed digital nerve.
