Neuropathic-like knee pain and associated risk factors: a cross-sectional study in a UK community sample.

BACKGROUND: Neuropathic-like knee pain (NKP) is often reported in individuals with knee pain (KP), but the contribution of specific central and peripheral risk factors to NKP has not been studied previously. The aims of the present study were to determine the prevalence of NKP in a community-derived sample with KP and to identify risk factors associated with NKP.

METHODS: A cross-sectional study was undertaken (n = 9506) in the East Midlands community among responders (aged 40+ years) to a postal questionnaire. Questions included KP severity (numerical rating scale) and type (neuropathic versus nociceptive) using the modified painDETECT questionnaire, as well as age, body mass index (BMI), significant knee injury, widespread pain, pain catastrophising and fatigue. Multinomial regression analysis was used to determine ORs and 95% CIs. Risk factors were categorised into central and peripheral, and proportional risk contribution (PRC) and 95% CI were estimated using ROC.

RESULTS: KP was reported in 28.2% of responders, of whom 13.65% had NKP (i.e., 3.9% of the total population). Women reported more NKP. After adjustment for age, gender, BMI and pain severity, definite NKP showed associations (aOR, 95% CI) with fibromyalgia (4.07, 2.49-6.66), widespread pain (1.93, 1.46-2.53), nodal osteoarthritis (1.80, 1.28-2.53), injury (1.50, 1.12-2.00), pain catastrophising (5.37, 2.93-9.84) and fatigue (5.37, 3.08-9.35) compared with non-NKP participants. Although only central risk factors contributed to NKP (PRC 8%, 95% CI 2.5-12.5 for central vs. PRC 3%, 95% CI -0.25 to 7.5 for peripheral), both central and peripheral risk factors contributed equally to non-NKP (PRC 10%, 95% CI 5-20 for both).

CONCLUSIONS: NKP appears to be driven largely by central risk factors and may require different prevention/treatment strategies.

TRIAL REGISTRATION: ClinicalTrials.gov , NCT02098070 . Registered on 27 March 2014.