Considering your age, every attempt to salvage the knee joint may be made and is justified. Visit your orthopedic surgeon once to confirm whether it is actually grade 4 OA.
If so, try to find a reason for the condition before proceeding for the surgery.
Next Steps
Surgery may be the only option but it needs to be done at a right time with a right set of investigations.
Health Tips
No hyaluronic acid in your case.