Fell off dirt bike 3 days ago, landed on knees. today my knee cap is very painful and can't bend/walk. i had x-rays and it's not cracked. any ideas?

Bruised knee cap: Direct fall onto knee without fracture can cause a painful swelling (bursitis) on the knee this usually will subside in 1-2 weeks with initial icing followed by heat and gradual range of motion exercises . A fall can also bruise the cartilage between the knee cap and the femur (post traumatic chondromalacia). If pain persists see an orthopedist or physical therapist for evaluation