Introduction
After failure of HA injection in patients with knee osteoarthritis, surgery is often the only alternative and, despite progress, total knee prosthesis is a restrictive surgery at 65 years old. The main objective of our study was to test a specific combination of HA+PRP (prepared using the A-CP HA Kit Cellular Matrix, Regen Lab SA) in patients with knee osteoarthritis who had an unsatisfactory clinical response to treatment with HA alone. This study was a prospective, non-controlled, multicenter trial.

Methods
From September 2013 to April 2014, 76 patients (35 females and 41 males, aged between 40 and 84 years old, mean age 63 years old, mean BMI 26.83), suffering from knee OA of Kellgren Lawrence grade II (33) and III (38), who had an unsatisfactory clinical response to HA treatment in the previous 3 months, and not taking analgesics or NSAIDs or anti-OA in the previous 3 months, were enrolled.
Patients were injected with Cellular Matrix at Day 0, Month 2 and Month 6 and were evaluated at these time-points and at a final follow up at Month 9. If effusion was present, an arthrocentesis was done before injecting the product into the joint. Pain was evaluated at the above time-points using the WOMAC scale (where the severity of symptoms was assessed on a 0-10 mm VAS).

Results
At month 9, 94.4% of the treated patients were considered responders to treatment based on the OMERACT_OARSI criteria. There was a significant difference in the WOMAC pain scale at Month 9 compared with Day 0 (mean values 1.89 vs 5.75, respectively). The difference in the WOMAC pain scale was also significant at Month 2 vs. baseline following 1 injection (3.62 vs. 5.75) and at Month 6 vs. Month 2 following the second injection (2.49 vs. 3.62). There was no significant difference in pain scores between radiological grade II and III nor between subgroups with differing BMI. No severe adverse events were reported.

Conclusion
This multicentre, prospective, 9 month study in patients with knee OA, demonstrated that 3 injections of Cellular Matrix, HA+PRP prepared using the A-CP HA Kit, represent a new medical alternative to knee surgery in patients who do not have a satisfactory response to treatment with HA alone.
These results appear to be encouraging and require further studies to better confirm the best treatment regimen.