My DD had something very similar to this when she was 14 months old. For over a week she ran a fever and just wasn't herself. She wasn't sleeping well and wasn't eating well. She was only 14 months old so she couldn't tell me what hurt, but she was fussy. I took her to the doctor TWICE. He looked in her throat and her ears and told me she was fine. He said that she is probably teething or has a touch of a virus. She was my first child so I believed him. Well, just exactly one week after I took her to the doctor the first time, she woke up from her afternoon nap kind of limping. She also would not bend one of her knees. I noticed that because she wouldn't bend over to pick up a favorite toy. I also took her outside and she normally would climb a certain hill, but she wouldn't even try. I felt her knee and it was warm. DH was out of town for work so I called my mom to ask what to do. She told me to bring her to the ER. I brought her in, and after talking to the nurse I could tell she was concerned. She called an orthopedic doctor in and he stuck a needle in her knee. Pus came out. They did emergency surgery on her that NIGHT at 10:30 PM! He told me that it had been a strep infection that wasn't treated. It had settled there in her knee. If they would not have gotten the infection out ASAP, it could have eaten away the knee, leg, or even been deadly. She was in the hospital for nearly 2 weeks on IV antibiotic. BTW, the rash had started to develop that very night. The doctor had noticed some of the spots on her chest. I had not noticed that. My focus had been on her leg/knee.
Needless to say I was FURIOUS at our pediatrician. We switched doctors right away!
She is healthy and fine today. I thank God for that! She has a scar, but she is fine.