The foot acts as an interface between the ground and the forces of the body. As it becomes a brake when the heel strikes the ground, it becomes a propeller at toe push-off. In between these two stages, the foot acts as a shock absorber for the body.
At the beginning of the walk cycle the foot contacts the ground on the outside (lateral) aspect of the heel. From this point, the passage of force then moves up the outside aspect of the foot, around the instep and over to the big toe. Then finally out through the large toe.
All five of the metatarsal joints make up one of the shock absorbers. Underneath each of these joints are nerves which feed between the web of each toe to its end. As these bones collapse, discomfort may occur under the ball of the foot or extend out to the toes. These conditions are called Metatarsalgia and Mortons Neuroma. Metatarsalgia is simply an inflammation of the fluid-filled sacs or bursa which are located under each of the lesser metatarsal heads. Morton Neuroma is a benign tumor or enlargement of one of the nerves that travels under and between the metatarsal heads.
Symptoms of Metatarsal Pain & Mortons Neuroma
When you stand and put weight on your feet, you may experience what feels like a bruise on the bottom of your foot behind your toes. As you start walking, this feeling most likely turns to burning, sharp pain, electrical shocks to the toes, or possible numbness to a couple of toes. In addition to this discomfort, you will sometimes feel like your socks are balled-up under your toes. Callouses may also appear across the ball of the foot where metatarsal heads are protruding through the fatty pad.
Cause of Metatarsal Pain & Mortons Neuroma
There are many reasons for this condition, including trauma and stress fractures. Yet the main cause is when the foot excessively pronates, causing the big toe to push up and move towards the second toe. The 1st toe therefore stops bearing its share of the weight and the weight is transferred to the 2nd, 3rd, and 4th metatarsal heads. The first metatarsal is wider and has two sesamoids to distribute the force, but the other metatarsals are narrow, so the force is concentrated in a small area.
When the symptoms are localized in this area, we have metatarsalgia. However, as more pressure is applied on the nerve going to the toes, the sheath which protects the nerve thickens, forming a benign tumor we refer to as Mortons Neuroma. Eventually the nerve tumor becomes so large that it can no longer sit under the ligament; and, if it drifts further out between the toes, the large base of the toe bones will pinch the tumor, causing sharp pains.
This excessive pronation can be due to trauma, genetic formation, ridged big toe joint, ankle fixation, leg difference, surgery failing to give adequate results, knee deformities, drop foot due to various systemic conditions, or, more often, to tight calves. Failure to address this issue may cause other treatments to fail.
Treatment of Metatarsal Pain & Mortons Neuroma
For both conditions, cortisone injections can be used to calm down the inflammation, but this gives only temporary relief and does not address the mechanical problem.
Shoes alone can give temporary relief for both conditions, more noticeable for metatarsalgia. In the long-term, shoes don’t solve the mechanical problem and the symptoms will increase in intensity. However, the success of the foot orthosis to achieve its goal relies on the foundation, called the shoe.
Surgery is used mainly for Mortons Neuroma and consists of removing the benign nerve tumor. It should be reserved for the most severe cases because it leaves the patient with numbness, sometimes permanent, between the toes and in an area about the size of a quarter in the bottom of the foot. Numbness is not desirable but may be an acceptable tradeoff if the pain is severe.
Foot Orthosis have been successful in treating both metatarsalgia and Mortons Neuroma by correcting the underlying cause: mechanical imbalance. By dropping the 1st metatarsal and redistributing the weight bearing more evenly over the entire plantar surface of the foot, the pressure is removed from the lesser metatarsals and transferred back to the 1st metatarsal. The passage of maximal force through the foot is restored to a more ideal pathway. This also takes additional pressure off the nerve. Over 90% of the clinical cases will respond favorably when treated conservatively in this way. Additionally, it has the benefit of preventing similar masses in adjacent interspaces and simultaneously rebalancing the rest of the musculoskeletal system.
The majority of those with over-pronation and metatarsal pain will find a regular stretching program involving the calves/Achilles tendon and plantar fascia important to the success of all treatment. The stretching exercise at the end of this page has been recommended by the American Orthopaedic Foot & Ankle Society.
Adding rockers to the bottom of the shoe(s) may provide additional reduction of the pressure on the metatarsals, after foot orthosis and stretching.