Possible Neuropathic Pain in Patients with Osteoarthritis of the Knee Before and After Total Knee Arthroplasty

PURPOSE: Although the pain of osteoarthritis (OA) is traditionally considered to be nociceptive, some patients also have neuropathic pain. The objective of this study was to evaluate the presence of 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 prospectively. The prevalence of neuropathic pain, unclear pain, and nociceptive pain in the knee was determined before and after TKA 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% 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. Knees with possible neuropathic pain postoperatively had higher postoperative NRS scores than those with nociceptive pain. CONCLUSION: Although the prevalence of possible neuropathic pain decreased significantly after TKA, the preoperative presence of possible neuropathic pain might be associated with the development of persistent postoperative pain following TKA.