A 65 year old lady presents with worsening pain in both knees for 3 years.

She is unable to walk for more than half an hour at a stretch because of the pain, which is exacerbated by kneeling, squatting, or descending the stairs.

Both knees are stiff for around 20 minutes after waking up; the stiffness as well as the pain are relieved by resting.

There is no history of pain, stiffness or restriction of hand movements. Her medical and drug histories are unremarkable.