Preoperative neuropathic pain like symptoms and central pain mechanisms in knee osteoarthritis predicts poor outcome 6 months after total knee replacement surgery

Preoperative pain characteristics in patients with osteoarthritis may explain persistent pain after total knee replacement. Fifty patients awaiting total knee replacement and 22 asymptomatic controls were recruited to evaluate the degree of neuropathic pain symptoms and pain sensitization. Patients with OA were pain phenotyped into 2 groups based on the PainDETECT questionnaire: high PainDETECT group (scores ≥19) indicating neuropathic pain-like symptoms and low PainDETECT group (scores <19) indicating nociceptive or mixed pain. Cuff algometry assessing pain detection thresholds and pain tolerance thresholds was conducted on the lower legs. Temporal summation of pain was assessed using 10 sequential cuff stimulations and a von Frey stimulator. Conditioning pain modulation was assessed by cuff pain conditioning on 1 leg and parallel assessment of pain detection thresholds on the contralateral leg. Pressure pain thresholds were recorded by pressure handheld algometry local and distant to the knee. Knee pain intensity (visual analogue scale) and pain assessments were collected before and 6 months after total knee replacement. Thirty percent of patients demonstrated neuropathic pain-like symptoms (high PainDETECT group). Facilitated temporal summation of pain and reduced pressure pain thresholds distant to the knee were found in the high PainDETECT group compared with the low PainDETECT group and healthy controls (P <.001). Patients with OA with high PainDETECT scores had higher postoperative visual analogue scale pain scores than the low PainDETECT patients (P <.0001) and facilitated temporal summation of pain (P =.022) compared with healthy control subjects. Perspective: This study has found that preoperative PainDETECT scores independently predict postoperative pain. Patients with knee OA with neuropathic pain-like symptoms identified using the PainDETECT questionnaire are most at risk of developing chronic postoperative pain after TKR surgery.