As per the X ray, there are changes related to Osteoarthritis in both the knee joints. Left > Right.
How much is he able to walk.
Role of injections is just for temporary pain relief.
It won't prevent the degenerative changes.
Next Steps
None of the medicines will have a permanent improving effect on the knee. most of the medicines are supplements for improving the cartilage quality.
Health Tips
He can wear knee support while he is walking, start knee strengthening exercises. Avoid heavy work, avoid sitting down, avoid stair climbing and descending. Analgesics,
calcium and vit d supplements can be taken.