Possible neuropathic pain in patients with osteoarthritis of the knee before and after total knee arthroplasty

Background: Although osteoarthritis (OA) is traditionally considered to be nociceptive, our objective was to examine neuropathic pain in the knees of OA patients using the painDETECT questionnaire (PDQ). Methods: : A total of 180 knees in 158 consecutive patients who underwent total knee arthroplasty (TKA) were enrolled. The prevalence of neuropathic pain, unclear pain and nociceptive pain was determined before and after TKA. Knee pain was evaluated using a numerical rating scale (NRS). All patients were evaluated preoperatively and 6 months postoperatively. Neuropathic pain and unclear pain were grouped together as possible neuropathic pain. The relationship between possible neuropathic pain and pain intensity was evaluated. Results: : Before TKA, neuropathic pain and unclear pain were found in 10 and 30 knees, respectively. The remaining 140 knees were categorized as nociceptive pain. After TKA, the numbers of knees with neuropathic and unclear pain decreased to one and five, respectively. The prevalence of possible neuropathic pain decreased significantly from 22.2% to 3.3% (p < 0.001) after surgery. Among the six knees with possible neuropathic pain postoperatively, four had possible neuropathic pain preoperatively as well, while the remaining two patients had been classified as nociceptive pain preoperatively (p = 0.021). Knees with postoperative possible neuropathic pain had higher postoperative NRS scores than those with nociceptive pain (p = 0.011). Conclusions: : The prevalence of possible neuropathic pain decreased significantly after TKA, however, preoperative possible neuropathic pain might affect the presence of persistent postoperative pain.