Though your bones are rubbing you can prevent further degradation / degeneration.

Since you have swelling and pain around the knee joint. You should go for waxbath and Ultrasound around the knee joint to reduce pain and swelling in the nearby Physiotherapy clinic and then you should start knee musculature strengthening and stretching exercises to decrease the load on the knee joint.

I think pt has severe arthritis. Avoid cross legged sitting on floor, avoid squatting and avoid using Indian toilets,

Avoid sitting Cross legged. Avoid Squatting- 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).

Arthritis OA so tk physiotherapy treatment must

We need more information regarding your pain.... Is this pain sudden after an injury or a long ignored pain... Further clinical evaluation is also necessary to ensure that there is no degenerative ligament or meniscal tear... For the time being you can put cold pack and some topical ointment

OA is the possibility, go for ice pack and ultrasonic till the swelling subsides. And then go for knee strengthening exercises and GOT with slight stretching of hamstrings and adductors and abductors to reduce knee loading.