Neuropathic Pain in Patients with Knee Osteoarthritis: Relation with Comorbidities and Functional Status

The aim of this study was to evaluate the prevalence of neuropathic pain components in knee osteoarthritis (OA) patients and to identify the relation between associated neuropathic pain and comorbidities, pain intensity, function, and radiographic severity of knee OA.

This cross-sectional study enrolled patients with knee OA (ACR criteria 1986). Visual Analog Scale (VAS) and DN4 questionnaires were performed for each patient. A score of DN4≥4/10 was classified as diagnostic for neuropathic pain. Functional impairment was estimated using the short form of the Knee injury and Osteoarthritis Outcome Score (KOOS-PS) and radiographs were rated using the Kellgren Lawrence (KL).

We recruited 101 patients with a sex ratio was 0.1. The mean age was 65.5 ± 10.8 years. The mean duration of symptoms was 3.5 years. At least one comorbidity was revealed for 88.1% of patients. Mean VAS pain was 6.5 ± 1.69. The mean DN4 score was 4.8 ± 2.4. The prevalence of NP (DN4≥4) was detected at 68.3%. The most frequently described NP characteristic was the sensation of burning (74%). The mean KOOS-PS score was 46.4 ± 19.2. Based on KL grading, 78.2% of OA were classified as grade III-IV. Female gender, number of comorbidities, bilateral knee OA, mean VAS pain, and mean KOOS-PS score were significantly higher in the neuropathic pain group when compared to the group without neuropathic (respectively: p = 0.01, p = 0.04, p = 0.017, p = 0.00, p = 0.00). In multivariate regression, KOOS-PS and bilateral knee OA were independently associated with NP.

Our results highlight the frequent NP in patients with knee OA (68.3%) and its relation with function and comorbidities.