The toe-box of running shoes is a critical part of the fit. This is the area that surrounds your foot from the ball of the foot (at the base of the toes) forward, housing the toes.
If this area does not fit you properly a number of potential injuries can occur, including: black (from dried blood underneath), ingrown, fungal, thick, or irregularly shaped toenails, blisters, painful corns and calluses, Morton’s neuroma (inflamed nerve), hallux limitus (jamming of the big toe joint), bunions (lump on side of foot at base of big toe with the big toe angled towards the 2nd toe), metatarsalgia (painful conditions in/under the ball of the foot), hammertoes (crooked toes), and arthritis of toe joints.
When putting on the running shoes, it is critical that your heel is all the way back in the shoe. To assure this, while seated with the shoe on, tap the back of the heel against the ground. Next, be sure to tie the shoes snugly enough so your foot does not slide forward in the shoe when you stand and walk, but not so snug that the lacing causes discomfort to the top of your foot or ankle. These steps are critical to perform before evaluating toe box fit, as well as every time you wear your shoes. Also, it is important when evaluating toe box fit to check BOTH FEET. No one has identical left and right feet. If only one of the shoes doesn't fit right, the shoes are no good for you.
The first area to look at is the length of the toe-box. For runners, this should be approximately a thumbnails’ length longer than your longest toe (beware: this will mean the 2nd toe for some people!). The reason that the extra room is needed in front is because when you land on your foot with the weight of your body from running, the foot spreads much more than when you land while walking, due to the much higher force of impact. Also, if you are running for more than just a few miles, your feet can begin to swell, also causing the need for additional room.
The second area to look at is the height of the toe-box (the shoe material over the toes and forefoot, called the “vamp” of the shoe). There should be enough space so that there isn’t pressure on the top of your toes and toenails. This is especially important for people with thick toe-nails or crooked toes that tend to not lay flat. If you cannot find shoes that have enough height in the toe box, try to find shoes with soft, expandable materials that do not have constrictive or stiff overlays. Slitting the vamp of the shoe directly above where a prominent toe is pressing, in an “X” manner, can allow an otherwise properly fitting shoe to work for you. Of course, do not cut into the shoe while your foot is inside.
Finding the right toe-box width and shape for your feet can be very simple or very difficult, depending on your own foot shape. I use the analogy; you can’t fit a square peg into a round hole (unless the peg is small enough).
Some people have feet where the toes are all relatively close in length – a “square type” foot, whereas, others have feet where the big toe or 2nd toe are much longer than the 4th and 5th toe, more of a “pointy” looking foot (Greek or Egyptian type). Also, some people have a very wide forefoot, especially those people with bunions (where the base of the great toe joint sticks out to the inner side).
Regardless of your foot shape, there is a simple way to assure that the toe-box of the shoe has the proper amount of space: remove both insoles from the shoes, stand on them with your full weight, and if your feet in no location overlap beyond the edges of the insoles, you’re good! The other properties of the shoes must be acceptable, but if they don’t pass this test, expect problems due to pressure from the sides of the vamp.
If the shoes you like are close to fitting properly in the width and shape, it is worth trying a half size larger in the same model, as the shoe will be proportionately wider and the maximum width of the shoe will be further towards the toes, potentially giving the needed amount of space. Also, inquire as to whether the shoe comes in widths. Women can consider trying a men’s version of the same shoe. If all else fails, you may have to try a different model or brand that has a shape more similar to your foot.