Background/Purpose:

Twenty to forty percent of patients with symptomatic knee osteoarthritis (OA) described neuropathic pain (NP). Several studies have shown that hyaluronic acid (HA) is an effective treatment of pain-associated knee OA. However, the impact of NP in the response to HA in knee OA is unknown as well as the impact of HA injections on the neuropathic profile of pain.

Our main objective was to assess the effect of NP according to DN4 score (10 items; NP if DN4≥4) in the response to HA in patient with moderate to severe symptomatic knee OA. Our secondary objectives were to assess the correlations between NP and baseline clinical and radiographic characteristics of knee OA patients and the effects of HA injections on NP.

Methods:

We conducted a post-hoc analysis from the 2012 HAPPYVISC study, a multicenter randomized, double-blind, non-inferiority prospective trial comparing the efficacy of 3 weekly intra-articular injections of 2 different HA at 24 weeks. At baseline, demographic, anthropometric, clinical data (VAS Pain, WOMAC score, NP assessed by DN4, presence or lack of synovial effusion) radiologic data (OARSI score for joint space narrowing [JSN]) were recorded. The symptomatic effect of HA was assessed by PGA, WOMAC, DN4 and OMERACT-OARSI response. All patients from intention-to-treat population with fully available DN4 data were included. Mann-Whitney and chi- square tests and multivariate logistic regression analysis were used.

Results:

187 patients were included. As baseline characteristics and treatment effectiveness were similar between the 2 HA groups, their data were pooled. Mean age was 64.7, sex ratio was 0.8, mean BMI was 27.7 and mean disease duration was 46.5 months. At baseline, mean VAS pain, WOMAC pain, WOMAC function were respectively 5.8, 9.7 and 27,3. Intra-articular effusion was present in 59 patients (31.6%). 79 patients (42.2%) had a OARSI grade 3 JSN. NP was present in 20 patients (10.7%). Most common positive DN4 items were tingling (36.9) and burning (36.4%). NP was significantly associated with pain intensity according to WOMAC pain score (p = 0.02). A significant association between baseline burning and VAS pain intensity was also found (p = 0.01).

At 24 weeks, 132 patients (70.6%) were OMERACT-OARSI responders. We found a significant association between OMERACT-OARSI response and overweight, obesity, and OARSI grade (p=0,01; p=0.0003; p=0.04). The presence of NP according to DN4 score at baseline did not impact the rate of OMERACT-OARSI responders to HA (p=0.32). On the other hand, the prevalence of patients with NP decreased by 50% (n=10) at 24 weeks after HA injections and there was an improvement of more than 75% of absolute DN4 value in 64 patients (34.2%). Most improved DN4 items were itching (90%), hypoesthesia to pinprick (88%), and burning (50%).

Conclusion:

NP is frequently described by symptomatic knee OA patients and is associated with pain severity. While NP does not influence HA response, AH reduces NP especially itching, sting hypoesthesia and burning.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-presence-of-neuropathic-pain-does-not-influence-the-response-to-hyaluronic-acid-ha-in-patients-with-knee-osteoarthritis-but-ha-injections-modify-pain-phenotype/