Background

Osteoarthritis (OA) is one of the major causes of knee pain and is detrimental to quality of life. Total knee replacement is the definitive treatment for patients with knee OA but there are some conservative treatments such as intra-articular injections of platelet-rich plasma (PRP) and hyaluronic acid (HA) that can be used to delay the need for knee arthroplasty. This study aimed to compare clinical, functional and health-related quality of life of PRP and HA intra-articular injections in patients with knee OA. The secondary aim was to identify the prognostic factors that may explain a superior outcome of KOOS total score at 12 months follow-up.

Methods

Prospective cohort study that included all consecutive adult patients (older than 18 years old) with symptomatic and radiographic knee OA that received intra-articular injection of PRP or HA. The exclusion criteria comprised patients who had previous knee surgery, had diagnosis of autoimmune or platelet diseases, took non-steroid anti-inflammatory drugs 3 days prior to injection or had history of repeated use of corticosteroids. An à priori power sample calculation assuming an alpha error of 5% and power of 80% showed that 90 subjects were required (45 in each group). A total of 100 patients (50 that had PRP intra-articular injection and 50 who had HA) with diagnosis of knee OA were included. Patients’ demographics and clinical characteristics at baseline were homogenous between groups, except from age, gender and Tegner scale. Patients submitted to PRP were 4.9 years older (p=0.015), were composed by a majority of women (64% versus 40%; p=0.016) and scored lower in Tegner scale (p=0.027). One week prior to the PRP or HA injection, patients received an intra-articular injection of 2 mL of Lederlon® solution which contains Triamcinolone Hexacetonide (TH) (40 mg) to decrease local inflammatory response. Clinical, functional and health-related quality of life outcomes were evaluated at baseline and 2, 6 and 12 months of follow-up by the Visual Analogue Scale (VAS), Knee injury and Osteoarthritis Outcome Score (KOOS) and the Short-Form 36 (SF-36).

Results

Both groups improved significantly from baseline to 12 months follow-up in the VAS, KOOS and SF-36 scores (p<0.001). The HA group showed a more significantly reduced VAS score compared to PRP group (p=0.005). All KOOS subscores and total score evolution overtime was significantly superior in HA group (p<0.001). Although both groups improved significantly the quality of life (majority of SF-36 subscores) at follow-up, there were no differences between groups at 12 months (p>0.05), except for the general health subscore (p=0.003). Age, intra-articular injection type (HA) and KOOS total score at baseline were prognostic factors for a superior improvement of KOOS total score from baseline to 12 months.

Conclusion

Both intra-articular injections PRP and HA proved to be effective treatments for knee OA, but injections of HA showed superior clinical and functional outcomes than PRP. Younger age, HA injection and KOOS total score at baseline were prognostic factors of superior KOOS total score at 12 months.