Consecutive patients with knee osteoarthritis and with a medical indication for viscosupplementation with hybrid hialuronic acid (HA) who fulfilled the inclusion criteria were recruited for the study. The inclusion criteria were: a medical indication for viscosupplementation therapy with hybrid HA; patients aged between 45 and 80 years; diagnosis of femorotibial gonarthrosis associated with femoro-patellar arthrosis or isolated, gonarthrosis symptoms for at least 6 months; patients who failed to respond to analgesics and/or regular NSAIDs, or were proved to be intolerant to the regular use of analgesics, NSAIDS, or weak opioids; grade 2 to 3 OA in the Kellgren-Lawrence grading scale ; pain when walking measured by the Visual Analog Scale of at least 40 mm on the targeted knee; and contralateral knee pain when walking with aVAS of less than 10 mm. The exclusion criteria were: inability to understand the aim of the study, inability to provide acceptable consent, pregnancy, serious ps

A single intra-articular injection of hybrid HA complex, Sinovial® HL (IBSA Pharmaceuticals, Italy, patent number WO/2012/032151 ) in the knee was performed from the lateral approach to the suprapatellar recess using ultrasound. For the ultrasound-guided infiltration method, a sterile linear probe with a 20 G guide was used to visualize the joint suprapatellar recess and avoid intrasynovial infiltration. The patient was positioned supine with the knee in full extension. From the lateral approach to the suprapatellar recess, HA was then injected into the knee joint, verifying intra-articular positioning in real-time via ultrasound imaging (direct visualization of viscous fluid or air bubbles).

Patients did not receive anti-inflammatory or pain-relieving drugs in the week before the first injection . Patients were evaluated at four time points: at baseline and after 28, 42, 84, and 168 days after the intervention. At each evaluation, clinical data relating to the status of the disea

Visual Analog Scale for the assessment of the pain during the study. Scale 0 ( no pain ) to 10 ( extreme pain )

The Western Ontario and McMaster Universities Arthritis Index ( WOMAC ) is used to assess the function of the knee in osteoarthritis. Scale 0 ( the worst result ) -100 ( the best result )