Background/Purpose:  Widespread
pain (WSP) is associated with morbidity, and poor mental and physical
functioning, but its etiology is not well understood. It has been hypothesized
that painful peripheral pathology may result in WSP. Previous cross-sectional
studies have shown an association of knee pain and radiographic knee osteoarthritis
(ROA) with WSP.  However, the independent
relations of knee OA and knee pain, to incident WSP is unknown. We examined the
relation of ROA, symptomatic knee OA (SxOA) and
consistent frequent knee pain (CFKP) to incident WSP in a large prospective
cohort.

Methods:  We
used data from the Multicenter
Osteoarthritis (MOST) Study, a NIH-funded longitudinal prospective
cohort of 3026 older adults with or at risk of knee OA. ROA was defined as
having radiographic tibiofemoral OA (Kellgren & Lawrence grade ≥2) on the 60-month
radiographs. The definition of CFKP was met if a participant reported knee pain
on most days during the past month at the 60-month telephone interview and at
the clinic visit that occurred on average one month later. SxOA
was defined as having both ROA and CFKP at 60 months. We also considered knee
replacement as equivalent to ROA and SxOA. WSP was defined as pain above and below the waist, on both
sides of the body and axially, using a standard homunculus, excluding knee pain.
Incident WSP was defined as presence of WSP at 84 months among those who were free
of WSP at 60 months. We assessed the relation of baseline ROA, SxOA,
and CFKP, respectively, to incident WSP using logistic regression, adjusting for baseline age, sex, BMI, comorbidities, physical activity, WOMAC pain
intensity, study site, depressive symptoms, pain catastrophizing and fatigue.

Results:   At baseline, 1309 subjects were
eligible for ROA analysis (age mean, SD; 67.3, 7.8; BMI 30.5, 6.0 kg/m²,
56% women), 1316 for SxOA analysis (age 67.3, 7.8; BMI 30.4, 5.9 kg/m²,
55% women) and 1383
for CFKP analysis (age 67.4, 7.8; BMI 30.5, 6.0 kg/m², 55%
women). Baseline
presence of unilateral ROA was associated with a non-significant 30% lower risk
of incident WSP compared with those without ROA (adjusted OR 0.70, 95% CI
0.46-1.07, p=0.10). Similar results were found for those with bilateral ROA. Similarly,
neither baseline unilateral nor bilateral SxOA were associated with risk of incident WSP compared with
those without SxOA. Baseline presence of unilateral CFKP
was also not significantly associated with incident WSP, while bilateral CFKP approached
significance (see table).

Conclusion: Neither
ROA, SxOA nor CFKP increased the risk of developing WSP.
These results suggest that neither knee joint pathology nor joint pain are major
factors in the onset of WSP. Further study is required to clarify what factors
contribute to the onset of WSP.

Table: Risk of ROA, SxOA and CFKP
to incident widespread pain

^[*] Adjusting for age at 60 mo, sex, BMI, comorbidities, physical activity
at 60 mo, clinic site, CES-D, catastrophizing, sleep/fatigue, knee pain severity.