As it currently stands for chiropractic services, Medicare only covers adjusting the spine.
No coverage is provided for extraspinal treatment, e.g., for knee, shoulder, wrist, ankle, etc., problems. This is expected to change; chiropractors anticipate Medicare will eventually cover extraspinal problems.
Other essential services provided by chiropractors, also not currently covered by Medicare, are exercises; supports; home care, nutritional, or ergonomic counseling; stretches; and supplements.
Your chiropractor may prescribe / provide these services for you because they are essential to resolving your problem(s), but Medicare will not reimburse; you are responsible for payment.