Knee pain can have causes that aren't due to underlying disease. Examples include heavy physical activity, lack of use, injuries such as sprains or strains, sitting in a constrained area or sitting on knees for a prolonged period.
Next Steps
You should consult to Physiotherapist. Since how many days you have this problem and is there any history of previous injury. Sometimes many of things are missed in X-Rays.You need complete Assessment.Sedentary lifestyle may also be the reason.
Health Tips
Share your Blood investigation reports.Regular Physiotherapy session will surely help you.