What to Look For
The most important factor in buying running shoes for bad knees is to figure out what is causing your knee pain. Most runners feel knee pain from either overpronating, where their foot rolls in from the ankle with each stride, or underpronating, where their foot rolls outwards from the ankle. If you have low arches, you most likely fall in the first category; if you have high arches, you most likely fall in the second. Overpronaters should search for shoes with extra padding on the midsole, near the arch, to protect their foot and properly distribute their weight as they run. Underpronaters, on the other hand, should find stability shoes that block their outward motion. These shoes are made of stiffer materials and keep the foot in place as they run. If you are a neutral runner with knee problems, you should try a flat-soled shoe, which will help you regain your natural stride.
One of the leading causes of knee problems, cheap materials in running shoes, can hurt runners in the long-term. You need to find a shoe with a flexible yet sturdy sole, good lining on the inside, a solid heel cup that doesn't let your feet slip, and a breathable mesh outer. While you might save a little money in the short term buying your shoes at discount stores, you'll end up paying it back many times over in medical bills later on.
Where to Buy
The first time you purchase a new pair of shoes, especially if you are buying a pair of shoes from a brand you've never before tried, make sure that you try them on in person to get the proper fit. Because of this, your best bet for running shoes for bad knees is a local running store, where employees can help you find the best pair for you. Chain stores also carry a wide variety of shoes, though their staff may be less helpful. Finally, you can find discounted shoes, sometimes by as much as 25 percent, online; however, don't try to purchase running shoes online until you've already tried on the same pair in person.
As of December 2011, it is possible to buy running shoes for as little as £25 at discount stores. However, for injury-prone runners, these shoes will do more harm than good. With running shoes, you get what you pay for: expect to spend between £50 and £75 on the best pair of running shoes.