This is not an easy question to answer in the general sense, however Physiotherapists are first contact practitioners. This means you can come straight to see a physio about your problem without seeing your doctor first. Physiotherapists are trained and qualified to assess and diagnose your condition and will liaise with other providers that may be of benefit to your care.
For example, if you come in for a physiotherapy appointment for an ankle injury, your physio can refer you for an xray to ensure the ankle is not broken. They can also apply immobilisation like a moonboot or cast to help it heal as well as assisting with therapies to reduce swelling and bruising to aid in maintaining the mobility of your ankle. The physio will let you know whether you can put weight through the ankle and show you how to use crutches or walking aids if they are needed. The physiotherapist may also suggest you speak with your pharmacist or GP about medications that may assist with managing your pain.