Mechanistic and Clinical Study of Intra-articular Arthrosamid for Knee Osteoarthritis

Prior to surgical intervention, the conservative treatment of knee osteoarthritis involves analgesia and intra-articular injections. Currently only steroid injections are available as part of NHS treatment. It is recognised they have short-term benefit only (<6months) and potentially have detrimental effects on residual cartilage. Arthrosamid is a hydrogel consisting of 97.5% sterile water and 2.5% cross-linked polyacrylamide. It's been shown to be safe and effective, with benefits lasting beyond 2 years in the majority. However, currently it is unclear via what biological pathways it reduces joint inflammation and pain.

Patients with osteoarthritis who are offered an intra-articular knee injection as part of standard care will be asked to enter the trial. On entering the trial baseline outcome measures will be recorded. The level of knee pain will be evaluated using Visual Analogue Scale (VAS). Patients will also be asked to complete the Knee injury and Osteoarthritis Outcome Score (KOOS) score and Western Ontario and McMaster Universities Arthritis Index (WOMAC). Patients will also declare the quantity of anti-inflammatory drugs and Oral analgesia that they have consumed.

At the time of treatment, a blood sample will be taken and under sterile conditions, synovial fluid will be aspirated from the knee prior to 6mls of Arthrosamid being injected. Patients will be reviewed by a researcher in a dedicated research clinic at 3,6 and 12 months post injection and the outcome measures repeated. At 3 months post injection synovial fluid and blood will again be collected from the patients. The blood and synovial fluid pre and post injection in patients who respond well to the injection will be compared to the samples from patients who fail to respond. The differences between the biochemical environments will allow us to identify likely pathways by which the injection reduces pain and inflammation.