As a physiatrist, or a physical medicine and rehabilitation doctor who sub-specializes in interventional spine and joint pain, I think of our field as, essentially, primary care for musculoskeletal medicine. Our field is ideally suited for aggressively diagnosing and conservatively treating most musculoskeletal medical problems.
Depending on the problem, depending on the diagnosis, physiatrists can help to coordinate the entire care from physical therapy, when appropriate, to the modalities that physiatrists have available at their disposal. Physiatrists can refer to other specialties like neurologists for neurological problems that fit more within their discipline, or rheumatology, or surgery when surgery seems like an appropriate consideration.