Here are the tips on PF from my book 200 Tips Every Runner Should Know, available on Amazon. Sorry about any formatting errors. It's a cut and paste from the Kindle version.
43. Runners Knee and Plantar Fasciitis
Chondromalacia (runner’s knee) and plantar fasciitis (sore arch or heel) are two of the most common running injuries. These injuries can be serious, taking weeks or months to heal. Motion control shoes or custom orthotics might help, but there are two less expensive options worth considering.
Off-the-shelf orthotics might provide all the support you need. An added benefit is that you might be able to switch to a lighter, more responsive running shoe. But if off-the-shelf orthotics don’t resolve your problem, you can build your own orthotics. This strategy has saved me hundreds of dollars in orthotic costs. If you need orthotics, the next tip is worth the price of this book many times over.
44. Build Your Own Orthotics for 20 Cents
You can make your own orthotics for a few pennies. You’ll need a pair of scissors, duct tape, and a square foot of craft’s felt (available at the crafts section of discount stores). Cut the felt into a few 1½ x 2-inch rectangles. Take the existing insert out of the shoe.
Add a few of these small pieces of craft felt to the bottom of the insert in the arch area. Overlap the felt to avoid getting all the bulk in one place. Use a small strip of duct tape or athletic tape to hold the felt in place. Put the insert back in the shoe and jog a bit. If you can’t feel any difference, keep adding pieces of felt until it feels like you’re walking with a tennis ball under your arch. When you reach that point, it’s a little too much, so remove one piece of felt. If you feel a pressure point where there is too much padding, make a mental note of where you need to make adjustments. With the shoe still on, slip your finger inside the shoe and put it on the spot where the padding must be removed.
Keep adjusting the felt by adding, moving or removing pieces as necessary. Repeat until it feels right. You want to feel support all along the arch, not just the front or the back or the outer edge. If it feels like you are running with a tennis ball under your arch, that’s too much. You can use pieces of any size—just fold or trim to give support in the area you need. Most likely, you’ll need 3-10 pieces on each arch, depending on how much arch support you need. Curiously, the number of pieces you need is not dependent on the height of your arch.
I have slightly below average height arches, yet I have to add extra arch support to all my shoes. Some shoe models require more additional padding than others. Also, the padding won’t be the same from one model year to the next or even from your left to your right foot. My right foot needs substantially more arch support than my left and yet, it appears visually the same as the left arch. Anyway, the outside edge of the felt should stick out past the inside edge of the insert. How much it needs to stick out varies with each shoe. For me, it’s typically a half-inch.
On your first run, you’ll probably need to make some minor adjustments. An easy way to do this is to wear a smartphone belt and carry blunt scissors, a few squares of felt, and a small roll of duct tape with you. Just stop and make adjustments during your run.
Bonus Tip: Don’t immediately go out for a 10-mile run after making a major adjustment to your shoes. Test it first on a short run. It’s possible to sprain the arch by providing too much support.
45. Modify Off-the-Shelf Orthotics
If homemade orthotics don’t work for you, you can even modify an off-the-shelf orthotic for a custom fit. Start with a two-piece orthotic, like Superfeet inserts, and add felt be-tween the hard-plastic bottom and foam part of the insert in the arch area.
I find that Superfeet Black plus felt work best for me in racing flats. In most performance shoes, I can just add a few pieces of felt to the existing insert.
This may sound like a lot of work, but it’s faster than a trip to your doctor’s office. Once you’ve made your own orthotics a couple of times, you can complete the entire process in less than ten minutes.
Bonus Tip: Once you make orthotics for your running shoes, you should consider making similar homemade orthotics for your casual and dress shoes as well. After all, you’ll be spending more hours in those shoes than your running shoes. This is especially important if you are recovering from an injury.
46. Tilt Orthotics to Reduce Pronation
Overpronation is a major cause of running injuries, so shoe companies make two types of shoes to resolve this common problem: motion control shoes for severe overpronation and stability shoes for moderate overpronation. As you’ve already learned, these shoes don’t always resolve the problem.
Fortunately, you can use the orthotics you made in the previous tip to also prevent overpronation.
The first step is to provide more arch support, which you can do by adding an off-the-shelf orthotic like Superfeet or building your own orthotics as described earlier. This might be enough, but you’ll probably also need to tilt the foot slightly to the outside.
If you look at custom orthotics, you’ll see two common characteristics. The first is that they provide more arch support than the factory insert that comes your running shoes. The second is that they often tilt the heel by raising the inside of the heel higher than the outside. This extra tilt helps reduce pronation by tilting your foot slightly to the outside upon foot strike.
You can tilt your homemade orthotic to accomplish the same thing by cutting a ¾-inch wide strip of craft’s felt and running it from the back of the heel towards the arch along the inside edge of the insert. Trim the felt conform to the curve of the insert. Then, tape it in place. Put the insert back in the shoe and take a step forward as described in the “Build Your Own Orthotics” tip. If your ankle still rotates inward, remove the insert and add another strip.
Depending on your degree of pronation, you may have to add more or less felt in the heel area. On some shoes, I have to add two layers. On other shoes, I don’t have to add any at all.
It’s amazing how much difference this will make in the feel of the shoe.
Bonus Tip: After an MCL sprain, I had recovered to the point that I could walk without pain, but when I wore hiking boots the pain returned. Why would I be able to walk without pain in all my shoes except these? Walking mindfully, I realized I was pronating. I added one piece of craft’s felt along the heel as I just described and the pain disappeared. Craft’s felt is only 1mm thick, yet that tiny change in tilt of the heel fixed the MCL pain!
47. Make Orthopedic Shoes
After ten years of making my own orthotics, it occurred to me I could improve the approach by modifying the outsole of the shoe itself. My right foot pronates so badly in some shoes that adding more felt to the heel became uncomfortable, so I thought: why not tilt the entire shoe?
To do this, turn the shoe upside down. Use Shoe Goo or glue from a hot glue gun to build up the outer sole of the shoe along the inside edge of the heel. This strip should be about a ½ to 1-inch wide and about 1/4-inch thick. Start at the back of the heel and go forward 2-3 inches.
After the glue dries (24 hours), put on the shoes and try the step forward test again. It’s okay to still pronate a bit, but it should be noticeably reduced. Next, run for a minute and see how it feels. If it feels like there’s too much tilt, adjust it by simply running a few steps while scuffing the bottom of your shoe along the pavement. You’ll grind off a little of the glue with each step. Repeat this process, reducing the thickness of the glue layer until it feels right. The great thing about the Shoe Goo method is if you mess it up, you can just peel the Shoe Goo off and start over.
Bonus tip: Once you master this approach, a more advanced method is to use a utility knife to cut off some of the outside edge of the outer sole instead of building up the inside edge. If you try this, be conservative. You can’t add the outsole back after you cut it off!
I’ve been doing this for years, but shoe manufacturers are catching on to this idea. Several new shoe models now have more thickness on the inside of the heel higher than on the outside. This allows the shoe to tilt outward upon impact, lessening the risk of overpronation.
Bonus Tip: Practice on an old pair of shoes first.