A 4 years old boy came with the complaints of sudden pain in the right knee joint which radiates upto the foot. He also complaints that he couldn't walk when he wake up at morning. He didn't complaints of any rise of temperature or swelling of the knee joint. His mother coplaints that the boy did not allow to touch his right leg. With these complaints he was taken by his parents. In past history his mother told that, after 2 years complete he sometimes complaints of pain and burning sensation in both the foot and was treated by Calcium tablet for 2 months. On examination temperature was 98 degree F, pulse normal, knee joint had no swelling or redness or tenderness. On laboratory investigation his ASO titre was 200 and C-reactive protein was negative. What is the diagnosis of this case? Is there anybody who can help me? And what is the treatment of this case? Is there any queiry, please mail me. Thank you Dr. Md. Sharif Hasna MBBS