If you have tried physiotherapy and the ankle remains persistently painful and swollen, it means that it was not a "simple ankle sprain". We need to do a thorough investigation to find out what structure has been injured.
An MRI would be recommended as it could visualize the soft tissue better. It could be hairline fracture, a ligament tear or an osteochondral injury (a small part of the bone/ cartilage has been chipped off).
Once we have established the diagnosis, then we can start the appropriate treatment. A simple sprain/ minor tear in the ligament could be treated conservatively with medication/ immobilisation and a further course of physiotherapy. if the ligament was partially torn/ completely torn, a platelet rich plasma injection/ surgery might be needed.
Similarly, a small osteochondral injury could be treated conservatively with medication/ immobilisation. A large displaced osteochondral fragment would require a surgical fixation.
As there are many possibilities with regards to your ankle, I would suggest you to go for a thorough check and examination by an Orthopaedic Surgeon and we would be able to advise you further.
Hope it clarifies some of your doubts.
Dr. Henry Chan
MBBS (Singapore), MRCS (Edin), M.MED (Ortho), FRCS Ed (Orth)
Consultant Orthopaedic Surgeon
HC Orthopaedic Surgery
Mount Elizabeth Hospital (Orchard), #15-14