Twisting injuries of knee are very common, two things could happen: one, the cartilage that works as a shock absorber (menisci) might get damaged or the ligaments that holds the knee bones together might get stretched or torn. There are two sets of such ligaments one, the cruiciates and the other the collaterals. From your description it is not easy for me to arrive at a diagnosis. Often injury to the menisci will render the person totally incapacitated to walk immediately because of the severity of the pain. Swelling which is not seen in the beginning may appear after 6-7 hours.
On the other hand, a ligament tear patient may hobble around and may continue his work but often swelling comes immediately. The physical signs on clinical examination may be difficult in the acute stage. However, after 2-3 weeks careful examination by an orthopaedic surgeon, should give clues to the correct diagnosis.
In view of your pain in the finger joint there is a third possibility. You could be having early degenerative changes in the knee joint which became apparent with the sudden stress of twisting at sea. Some times early degenerative changes could be part of another condition called gout. This can be easily diagnosed by testing your blood for serum uric acid. Whatever be the nature of your problem, there is one exercise that is most beneficial - keeping your leg straight at the knee and tightening your knee cap against the bones that form the knee. This is called isometric exercises for your quadriceps (front of thigh muscle). This muscle wastes rapidly in any problem of the knee and most functions of the knee can be maintained with good quadriceps. You could ask your physiotherapist to teach you if you could not figure out what I have just written. You will need to do this 3-4 minutes by the clock every hour. It takes about 3-6 weeks to show its benefit.