What can be done for an injured foot/ankle and loose ligaments?

Conservatively: You can strengthen tendons that run near the ligaments, you can brace the door if unstable and then you always have the surgical treatment of fixing the damaged ligament.

Ankle injury: First rest, ice, compression, and elevation. Second bracing can help compensate for loose or ruptured ligaments.

Prolotherapy: Loose ligaments that do not provide adequate skeletal support can be strengthened by a technique known as prolotherapy. I have used it for 15 years with excellent success in most cases.