Scientists investigate why knee pain varies so much between patients

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Knee pain for greater than 6 months. * Moderate-to-severe knee pain (\>3/10) due to osteoarthritis, as defined by American College of Rheumatology and EULAR diagnostic criteria, on \>50% of days in the past month. * KL grade 2-4 indicating significant degenerative changes on knee X-ray. * 45-80 years old Exclusion Criteria: * Inflammatory arthritis (e.g. rheumatoid arthritis). * More intense pain due to another chronic pain syndrome (e.g. fibromyalgia, hip osteoarthritis) * Significant pain or weakness in the lower extremities due to a neurological condition (e.g. lumbar radiculopathy, paresis due to stroke) * Acute pain that is more intense than knee osteoarthritis pain * Current routine use of more than 15 mg oral morphine equivalents per day (use of \<15 mg OME does not exclude the participant). * Recent new medication, exercise, behavioral, or complementary and integrative treatment started in the last month. Stable use of these treatments for greater than 1 month does not exclude the participant. * Recent intra-articular injection of steroid or other agent (greater than 1 month does not exclude the participant) * Recent knee radiofrequency ablation (greater than 3 months does not exclude the participant) * Recent knee arthroscopic surgery (greater than 3 months does not exclude the participant) * History of knee replacement or open knee surgery on the index knee, defined as the more painful knee on average over the last month. * Inability to walk or climb stairs without significant assistance (e.g. a one-person assist, use a wheel chair; however, the use of a cane does not exclude the participant). * Inability to participate in study procedures (e.g. cognitive impairment limiting ability to understand directions, inability to understand and read English) * Uncontrolled or unstable medical disorder preventing participation in study procedures * History of brain surgery * Tattoos on sensory testing sites * Pregnancy * Breastfeeding * Inability to under knee MRI scan due to incompatible devices or foreign bodies.