6 yr old has sever knee pain at night and cant walk?

Knee pain: If the pain is only at night and he walks well during the day he is probably ok. If the knee is swollen in the morning and he has difficulty walking he could have arthritis. Knee pain can also be pain referred from the hip. If he has not seen a physician, I would highly suggest seeing a pediatrician. Persistent pain should be evaluated further with possible X-rays and lab work.

Knee pain: Knee pain, swelling, redness, and warmth can be signs of a serious infection. Any child who cannot walk from pain should be seen promptly by a doctor.

Needs to be checked : Severe knee pain and can not walk needs to be checked by his Paditrician asap . Needs detailed history as to any trauma,associated symptoms like fever etc . And a physical exam, blood test and imaging like X-rays,MRI et . To make a proper diagnosis and appropriate treatment .