Background/Purpose:

Though pain is the cardinal symptom of osteoarthritis (OA) the underlying causes are not fully understood. However, peripheral and central sensitization has been suggested to play an important role in OA pain. The aim of this study was to investigate associations between mechanism based pain assessment parameters associated with peripheral and central sensitisation in painful knee OA and clinical manifestations (K&L, Pain intensity, WOMAC).

Methods:

217 patients with different degrees of OA pain (rated on a visual analog scale (VAS) from 0 to 100) and 36 healthy controls participated in the study. Patients were allocated into: controls (VAS 0-9), Group A (VAS 10-39), Group B (VAS 40-69) and Group C (VAS 70-100). Pressure pain thresholds (PPT´s) were measured in the peripatellar region, tibialis anterior and extensor carpi radialis muscle before, during and after conditioning pain modulation (CPM). Temporal summation to repeated mechanical stimulation was measured at all sites. A sensitization index was constructed based on PPT´s, temporal summation and CPM. Pain and soreness areas were obtained. The radiologic assessment of OA was made by specialists using Kellgren & Lawrence grading scale (0-4). 

Results:

All patient groups had significantly lower PPT´s compared to controls. Patients showed facilitated temporal summation and reduced CPM function compared to controls. Significant correlations were found between CPM effect (r=0.23, p<0.01), degree of temporal summation (r=-0.36, p<0.01) and PPT (r=0.22, p<0.01) and clinical Vas ratings. The index of pain sensitization revealed that 37.3 % of the patients were twice as pain sensitive as controls. The pain sensitization score was significantly was correlated with VAS ratings (0.36, p<0.01) and pain/soreness areas (r=0.14, p<0.05 and r=0.15, p<0.05)      

Conclusion:

Patients with mild, moderate and severe pain had significantly lower PPT´s compared to controls. Furthermore, patients with OA had significantly more central sensitization (decreased CPM effect and increased temporal summation) compared to controls. This study is the first to demonstrate a tool for OA patient stratification into sensitized and non-sensitized based on relevant pain assessment parameters. This stratification can be useful for diagnosis and future treatment of OA patients and for monitoring the effects of new drugs under the development for OA pain.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/peripheral-and-central-sensitization-in-patients-with-different-degree-of-knee-osteoarthritis/