Consult to an orthopedician to rule out is their is any osteoarthritis of knee.
Meanwhile go for contrast fermentation of knee and calf muscles(hot and cold therapy).
Next Steps
Go for calf stretching,Core Strengthening Exercise- Straight Leg Raised With Toes Turned Outward, repeat 10 times, twice a day. Hams Stretching- lie straight, take the leg up, pull the feet towards yourself, with a elastic tube or normal belt. repeat 10 times, twice a day. Quadriceps Exercises- Lie straight, make a towel role and put it under the knee, press the keen against the role, hold it for 20 secs. Repeat 20 times twice a day. This will help relieve some pain.