Cyst in my hip, can it be result of car accident? I diagnosed with subchondral cyst in anterior femoral head-neck junction. Also diagnosed with hip fai. Where is cyst come from? Is it result of impact? I never had a back lbp and hip pain before the accid

Arthritis. Subchondral cysts occur in arthritis. Fai predisposes you to arthritis of the hip, especially anteriorly. Accident usually doesn't cause arthritis so quickly.
It's . It's difficult to be sure how your particular condition developed. Fai is associated with cartilage damage, labral tears, early hip arthritis, hyperlaxity, sports hernias, and low back pain. Fai is common in athletes, but also occurs in active individuals. Since you've been diagnosed, you're likely aware of your treatment options. I would make sure that your orthopedic doctor has experience in treating fai. Good luck!