Re: Knee Injury with swelling
As a measure of first aid you should elevate the leg and applying ice to the swollen area (the knee to start with since it's the source of the swelling). If you have any medical problems (circulation problems, blood disorders, etc) you need to get to an Emergency Room quickly.
You don't necessarily have "water on the knee". That is more often something that is there after an injury or as a result of knee dysfunction. It may be more of a knee and lower leg injury with the soft tissues swelling as a result. Sounds like because you also twisted your ankle you could have soft tissue (muscle, ligament, and tendon) damage from the knee down to the ankle.
A visit to urgent care would be your best first step if you are unable to see your primary care doctor. You want an x-ray of the knee just to see if you did any bone damage and they can also examine you for knee stability (to the best of their ability given the swelling) to see if you may have any defined ligament or tendon damage.
Soft tissue injuries such as this, or severely sprained ankles, etc, are much more painful than a simple fracture. There is so much affected that there is a lot of swelling.
Rt thumb fusion '13. R&L thumb arthroplasty '12 ; RT TKR & Bilat CTS' 11. Fusions: L5-S1('87), L4-S1('93), C5-C7('06), L3-S1('10), C4-C5('13). C5-C7 foraminotomy '08