### instruction:
If you are a doctor, please answer the medical questions based on the patient's description.

### input:
I tripped 3 weeks ago and landed hard on my knee. The skin has heals and I only have minor road rash scabs on it - the lower part of my knee cap is very painful to the touch and I can not kneel on it at all. I can walk OK and I can bend the leg fine. Should I give it more time to heal or should I go it and get it check out - x-rays MRI?

### output:

Hi there. Thanks for your question at Chat Doctor.X-ray is indicated if 1. You are not able to walk on your affected knee(not able to take any steps without pain). 2. you are not able to bend and straighten your knee to the fullest extent(or your previous normal range of motion). 3. There are any areas of your knee which are very tender to touch(after you feel all the spots of your knee-all around). 4. If you are elderly, say more than 55 years (your chances of major injury increase with age). MRI of the knee may be useful in you case if at all to evaluate specific clinical scenarios like 1. Prolonged, refractory, or unexplained knee pain for more than 6 weeks 2. Mechanical knee symptoms: catching, locking, snapping, crepitus3. Tibiofemoral and/or patellofemoral instability: chronic, recurrent, subacute-associated with difficulty in climbing or getting downstairs etc. 4. Swelling with Limited or painful range of motion Since you can walk and bend ok, major ligamentous injury inside your knee is unlikely. Pain on kneeling with tenderness to touch indicate direct trauma at the site of injury which can be seen on x-ray. If pain does not subside in 6 weeks, MRI may be indicated. Hope this answers your questions the best Regards Chat Doctor. 