Watery feeling may be due to swelling or edema over knee.
Next Steps
to reduce swelling keep your legs on pillow ( height of your leg above heart level) ,
movement of knee,ankle and hip itself will help in reducing swelling),ice pack ,massage- in upward direction will also reduce swelling
Health Tips
static quadriceps exercise ( pressing knee down), hip, ankle,knee active movements, ultrasound machine and stretching will help you.
For further and proper treatment consult physiotherapist