Pain Expansion and Severity Reflect Central Sensitization in Primary Care Patients with Greater Trochanteric Pain Syndrome

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.

Chronic pain, whether the result of nerve trauma or persistent inflammation, is a debilitating condition that exerts a high social cost in terms of productivity, economic impact and quality of life. Currently available therapies yield limited success in treating such pain, suggesting the need for new insight into underlying mechanism(s). Here, we examine the likelihood that sustained activation of descending modulatory pathways that facilitate pain transmission could underlie some states of chronic pain. Such activation of descending facilitatory pathways might be the result of neuroplastic changes that occur at medullary sites in response to persistent input of pain signals. Understanding the mechanisms of descending facilitation and the spinal effects of such discharge could provide new insights into the modulation of chronic pain.

Emerging evidence suggests that pain sensitization plays an important role in pain associated with knee osteoarthritis (OA). This systematic review and meta-analysis examined the evidence for pain sensitization in people with knee OA and the relationship between pain sensitization and symptom severity.