Cartilage is devoid of nerves; so, while OA is pathologically a cartilage deficit issue, it is not a source of pain.
OA knee pain would come from either Bone Marrow Edema (BME) or synovial inflammation. Ultrasound can detect the latter, but MRI is needed for the former.
Detecting such lesions will enable a more targeted approach in alleviating knee pain.
I've got really bad news for those with OA knee: unremitting knee pain can lead to widespread pain in other joints not affected by OA. This in turn is associated with poor physical functioning and psychosocial problems.
This is due to "sensitisation". This apparently does not happen with pain from BMEs, but can (and often does) with synovitis. And it's independent of how structurally deranged the knee joint is.
The priority should then be to ameliorate the knee pain as early and as completely as possible, even if we can't reverse the joint damage.