Knee pain from diving for flags

Patient: Hi im 16 and play flagfootball for my school. Two weeks ago i dove repetitively in one game,I only ever felt the pain in one knee. When i got home my knee was swollen and my leg was bruised from the knee down. I have pain when I walk bend and especially when pressure is put on.So my parents made me sit out the next 2 games(1 week) my knee felt better although it was still bruised and swollen. I started to go back to practice, no pain was severe so i played a game Thursday. I dove for a flag and pain was awful. I went out of the game. My knee hurts the most it ever has, the muscle on the outside is tender and tight and on the inside below the knee cap. My parents have refused to take me to the doctor but im worried i pulled/strained something. What do you think is wrong

Symptoms: Symptoms:swelling,bruising,pain when walking/stairs,pain when put pressure on

Doctor: Welcome to Ask The Doctor.We are here to help you.You seem to be have developed acute knee sprain but you should r ule out any knee ligament injury. In such scenario, if the knee joint movement is fine, then we initially give 5 days conservative treatment and if there is no response, then we investigate.So, you should do cold ice fomentation of the knee and apply Diclofenac ointment locally. In case of severe pain, you can take Pain killers like Diclofenac if the pain is severe and there are no contraindications for its use. Avoid sitting in squatting position and climbing stairs.If you don’t get any relief after even 5 days of therapy, then you would require to get MRI of your knee joint done, to rule out any ligament injury.Share my opinion with your doctor before acting upon it.I hope it helps.Stay Healthy.