title: Sensitization in patients with painful knee osteoarthritis.
abstract: Pain is the dominant symptom in osteoarthritis (OA) and sensitization may contribute to the pain severity. This study investigated the role of sensitization in patients with painful knee OA by measuring (1) pressure pain thresholds (PPTs); (2) spreading sensitization; (3) temporal summation to repeated pressure pain stimulation; (4) pain responses after intramuscular hypertonic saline; and (5) pressure pain modulation by heterotopic descending noxious inhibitory control (DNIC). Forty-eight patients with different degrees of knee OA and twenty-four age- and sex-matched control subjects participated. The patients were separated into strong/severe (VAS>or=6) and mild/moderate pain (VAS<6) groups. PPTs were measured from the peripatellar region, tibialis anterior (TA) and extensor carpi radialis longus muscles before, during and after DNIC. Temporal summation to pressure was measured at the most painful site in the peripatellar region and over TA. Patients with severely painful OA pain have significantly lower PPT than controls. For all locations (knee, leg, and arm) significantly negative correlations between VAS and PPT were found (more pain, more sensitization). OA patients showed a significant facilitation of temporal summation from both the knee and TA and had significantly less DNIC as compared with controls. No correlations were found between standard radiological findings and clinical/experimental pain parameters. However, patients with lesions in the lateral tibiofemoral knee compartment had higher pain ratings compared with those with intercondylar and medial lesions. This study highlights the importance of central sensitization as an important manifestation in knee OA.
authors.affiliation: Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Aalborg University, Denmark Clinical Nursing Research Unit, Hobrovej 18-22, Aalborg Hospital, DK-9000 Aalborg, Denmark Northern Orthopaedic Division, Hobrovej 18-22, Aalborg Hospital, DK-9000 Aalborg, Denmark.
authors.forename: Lars
authors.initials: L
authors.lastname: Arendt-Nielsen
authors.forename: Hongling
authors.initials: H
authors.lastname: Nie
authors.forename: Mogens B
authors.initials: MB
authors.lastname: Laursen
authors.forename: Birgitte S
authors.initials: BS
authors.lastname: Laursen
authors.forename: Pascal
authors.initials: P
authors.lastname: Madeleine
authors.forename: Ole H
authors.initials: OH
authors.lastname: Simonsen
authors.forename: Thomas
authors.initials: T
authors.lastname: Graven-Nielsen
mesh_terms: D018771:Arthralgia / Q000000981:diagnostic imaging / Q000209:etiology* / Q000503:physiopathology*; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000033:anatomy & histology / Q000294:innervation / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000294:innervation / Q000503:physiopathology; D020370:Osteoarthritis, Knee / Q000150:complications* / Q000000981:diagnostic imaging / Q000503:physiopathology*; D010147:Pain Measurement / Q000379:methods; D017288:Pain Threshold / Q000502:physiology*; D011859:Radiography; D012720:Severity of Illness Index; D013997:Time Factors