Chronic sprained ankles are slow to respond and heal because tendons and ligaments are slow to heal. The healing rate of the collagen fibres and attachments can take over two years. You can read up about the rate of tissue healing by Professor Tim Watson. However, modern electrotherapy has been advanced greatly over the last 10 years so the healing can be increased by better methods. My dream rehabilitation approach is Anti Gravity Treadmills which cost around £28,000 and of course can be found in Premier League Football Clubs such as Arsenal and Manchester United.