Avoid sitting Cross legged.
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.
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.
Sports Taping- stretch the tape from both ends and apply on the affected area
Contrast Fomentation (Hot and Cold).
Find out why there is pain...get any x ray first
Then make use of ice pack over the for 10 mins and repeat it after every 1 hr for 8 times a day...
elevate the affected limb by keeping 2 pillows below it in sleeping position ...
any other more help required feel free to consult
Most probable cause at this age is osteoarthritis... It's a degenerative bone disease...There’s no cure for osteoarthritis as yet, but there are a number of treatments that can help ease symptoms and reduce the chances arthritis becoming worse...options are analgesics, NSAIDs,intraosseous steroid injection and hyaluronic acid injections,Physiotherapy like strengthening exercises etc ... Treatment depends upon the stage...I would suggest you to consult nearest orthopedic surgeon they will do the needful