How does the doctor know if the diagnosis is bone infection?

Exam, x-rays, labs. Pain, swelling, drainage, fevers, inability to walk, stiffness, lack of joint motion. Blood tests should be done and usually reveal elevated white blood cell count, elevated sedimentation rate, elevated c-reactive protein. Blood cultures and drainage cultures usually reveal the bacteria involved. Osteomyelitis is the technical term, and often requires hospitalization. X-rays can also help.
Bone infection. This can be diagnosed with different tests including an indium scan, mri, and blood tests.

Related Questions

Infection in toe, whole toe throbbing, doc appt monday, do I need to be seen immediately or can this wait? Worried about bone infection...

? fever, red lines? I suspect you may have an infected ingrown nail having had them myslef, they can be extremely painful. The big decision is can you wiat for three days. If there is no fever, there is no streaking up your foot/leg, and you are able to tolerate the pain until monday, then you can wait. Soak your foot in epsom salts, gently pull the overgrown skin away from nail. Take Ibuprofen for pain as needed.