Knee pain may either be sudden or gradual. It could be a knife in the back when going upstairs or a dull pain that never really subsides. Knee pain is one of the most frequent complaints of people of all ages, whether it is a result of an old injury or a new strain.
More info : https://jghdelhi.net/blog-post/why-does-your-knee-hurt-12-common-causes-and-when-to-see-a-doctor