Can a hip flexor injury cause pain to radiate into the medial knee during exercise?

Hip flexor injury. Pain from injury to the iliopsoas muscle is usually felt in the front part of the hip, depending on the extent of the injury.
Yes. Injury to your hip flexor a can alter your gait and cause pain down the kinetic chain and into your upper thigh and knee. I recommend stretching, mice, and rest. If no other health problems Motrin or aleeve is also appropriate.