Hello, As you mentioned you are not very active and were in the sitting position that triggered this pain. The likely cause is muscle spasm or nerve getting pinched. Also with age the strength of bones and joints weakens. I suggest, take sufficient rest and avoid heavy movements of the joint for couple of days or at least a week. Medications like ibuprofen can be used for pain relief and increase your dietary calcium intake. If the pain persists for more than a week, I suggest get an X-ray of the knees joint done. And seek medical advice from a rheumatologist. Couple of blood tests also need to be done if needed as per the doctor’s advice. Depending on the underlying cause further management will be done to improve your condition. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Manisha Auradkar, General & Family Physician