The warning follows a study suggesting that ankle sprains are best treated with exercise in the week after injury, despite earlier studies supporting conflicting advice.
UK researchers found that an accelerated programme of exercise soon after a severe sprain was more effective at improving ankle function than resting the injury.
The research contradicts a 2009 Lancet study, which concluded that immobilising the injury with a below-knee cast was the best treatment option.
But Dr Roderic MacDonald, president of the British Institute of Musculoskeletal Medicine, said that grouping all ankle sprains together disguises different causes, which may require more nuanced care.
'The idea that there is one treatment for any sprain is almost inevitably wrong,' he said.
Sprains could be due to stress on the joint, in which case standard care is irrelevant because there is no tissue damage, he said.
Dr MacDonald said specialists increasingly find that sprains are caused as much by damage to nerve receptors in the joint as by tissue damage.
Keeping patients active in these cases, therefore, is just as rational as resting those with tissue damage, he said.
For the latest study, researchers assigned 101 patients who had been recently admitted to hospital with a severe ankle sprain to one of two treatments.
For the first week after their injury, patients were treated either with an early therapeutic exercise plan, or given standard protection including rest, ice, compression and elevation.
Both groups were then given ankle rehabilitation exercises for the following three weeks.
Patients who had received early therapeutic exercise showed greater improvements to short-term ankle function.