The reasons vary from malnourishment syndromes to inflammatory disorders. You may consult with a Physiotherapist or a Physician who can screen your condition and refer to appropriate speciality if specialist management is required. Stress often flare up the condition and you need to manage it very well.
Next Steps
Seek professional advice without delay as delayed management erodes joint surfaces
Health Tips
observe what all factors flare up the pain and factors which soothes it. This may be helpful in gathering enough information to the specialist.