Improper fitting shoes are often a cause of foot, ankle, knee, hip and back pain.
You need proper fitting shoes from the counter or heel cup to stabilize the heel thus not allowing too much eversion or inversion of the heel during weight bearing.
A good shoe needs to have a good insole that supports your arch to not allow pistoning of your arch and plantar fascia. This can lead to plantar fasciitis or stone bruises in your heel and underside of your foot. The arch support of the insole needs to be high enough so that your forefoot will not pronate or supinate.
The shoelaces should be tied snug across the arch of your foot so that you cannot remove your shoes without untying the laces. If you can take your shoe off with laces tied, then you are not keeping your foot in contact with the insole of your shoe. This will lead to your foot coming off the insert with every step you take. Additionally, you will be hitting the insole each time you walk which will cause overstretching of the plantar fascia.
How you stand on the ground effects everything. The joints of your lower limb up to your back are aligned or misaligned by your stance. If you have flat feet you will tend to walk and stand more on the inside part of your foot and this causes your knees to go into genu valgus, putting more strain on the knee medial joint line. As you move up the chain, the hips and lower back will be out of alignment. All from improper fitting shoes and/or no support in arch of your shoes.
A proper fitting shoe with a well-fitting insert is key to support the type of arch you have. This will help align your heel and therefore keep the rest of lower body chain in alignment. Ultimately helping avoid strains and injuries to lower leg joints and the lumbar spine