Background: Patient's pain experience is a complex phenomenon. A comprehensive clinical assessment of the patient's pain experience is helpful to define individual differences between patients and thus to plan effective individualized treatment programs. Gait assessment is an important functional task in the clinical evaluation, which allows the definition and modulation of therapeutic intervention. The influence of patient's pain experience on gait parameters is currently understudied in literature.

Objective: To investigate patient's pain experience based on an assessment model proposed by Walton and Elliott in patients with knee OA. The study's second aim is to examine the correlation between the parameters of the 10 Meter Walking Test (10MWT) and Time Up and Go test (TUG) assessed by an inertial sensor and the patient's pain experience.

Each patient undergoes a clinical pain assessment including Western Ontario and McMaster University Osteoarthritis (WOMAC) scale, a patient-reported outcome questionnaire that aims to identify changes in symptoms and activity restrictions in subjects with OA. A guided clinical assessment explores nociceptive, neuropathic, nociplastic, psychological, beliefs, socioenvironmental, and sensorimotor disintegration domains. A series of assessment scales were considered for each patient: Pain DETECT Scale; Central Sensitization Inventory (CSI) Index; Patient Health Questionairre (PHQ-9); post traumatic distress checklist (PTSD); Pain Catastrophyzing Scale (PCS); Tampa Kinesiophobia Scale (TSK); Fear Avoidance Believe Questionnaire (FABQ), Injustice Experience Questionnaire (IEQ) and the completion of a body chart.

An assessment of pressure pain threshold (PPT) was conducted through an electronic algometer (Algomed). The defined sites for PPT were the patella, Gerdy's tubercle, and the forearm on the extensor digitorum. The examiner applied gradual pressure on the defined areas, and patients were asked to report the exact moment when the pressure began to change to a sensation of pain. At that time, the examiner terminated the application of pressure, and the measurement related to the PPT was taken.

Kinematic parameters were analyzed by two functional tests, the 10-Meter Walking Test (10MWT) and the Time Up&Go test (TUG). The tests were carried out with the help of an inertial sensor (BTS G-Sensor), placed at the trunk level, above the subject's clothing, via an elastic belt. 10MWT is a standard test used in gait assessment that consists of walking 10 meters in a straight line; TUG is a common and validated test that provides important indications about the level of balance and functional and walking ability of subjects. The test consists of getting up from a chair, walking 3 meters, turning around, returning to the chair, and sitting down. The inertial sensor registered the spatio-temporal parameters during 10MWT and TUG.

Inclusion Criteria:

Inclusion criteria for this study are age 50 and 90 years, Body Mass Index (BMI) <30 kg/m2, and Knee OA symptoms. OA is confirmed by the treating physician and radiographic findings (severity of OA 2 to 4 Kellgren-Lawrence scale).

Exclusion Criteria:

Exclusion Criteria are the presence of psychiatric or neurological disorders, peripheral nerve injury, uncontrolled inflammatory states, neuromuscular and rheumatologic diseases, dementia and language barriers, limiting orthopedic conditions (amputations, non-reducible joint limitations), post-traumatic OA (e.g., fractures), congenital hip deformities, hip surgery, Legg-Calvé-Perthes disease. Patients with degenerative or non-degenerative neurological conditions in which pain perception is impaired and ongoing corticosteroid infiltration, and bedridden subjects are excluded.

All patients presenting to clinic IRCCS Fondazione Don Carlo Gnocchi, Italy diagnosed with knee OA will be screened for eligibility.