You put a lot of stress on your hip flexors when you sprint or kick. Thatâs why athletes, especially runners, soccer players, and martial artists, are especially prone to hip flexor injuries that result in hip flexor pain. Hip flexor pain is usually felt in the upper groin region, where the thigh meets the pelvis. To avoid hip flexor pain, you should pay more attention to these muscles, Dr. Siegrist explains. When you are seated, your knees are bent and your hip muscles are flexed and often tighten up or become shortened.
Walking and bicycling are good exercises for bad knees because they aren't high-impact. If you belong to a gym, the elliptical machine is another good option; the machine has pedals instead of a flat, treadmill-like surface and allows you to simulate running and walking without the impact on the joints.
Knee injuries are something I know a bit about, thanks to a combination of skateboarding, snowboarding, judo, and Brazilian jiu-jitsu that has resulted in torn ligaments, torn cartilage, surgery on both knees, and enough hours on a stationary bike to last a lifetime.