As many as 15% of patients report at least moderate persistent pain after TKA. Such pain may be related the presence of widespread hyperalgesia and neuropathic-type pain. The study asked if there was a difference among patients who report moderate to severe pain or no pain at least 12 months post TKA regarding (1) pressure pain threshold, (2) thermal (cold/heat) pain and detection thresholds, and (3) self-reported neuropathic pain. Fifty-three volunteers were recruited from patients reporting no pain or moderate to severe pain, according to the Knee Society Score. Differences between the moderate-to-severe and no-pain groups regarding pressure pain, heat and cold thresholds, and self-reported neuropathic-type pain were analyzed using independent t-tests. Patients in the moderate-to-severe pain group exhibited reduced pressure pain threshold in the knee with the TKA (p=0.025) and at the elbow (p=0.002). This group also showed greater pain sensitivity to cold at the knee (p=0.008) and elbow (p=0.010), and increased heat pain sensitivity at the elbow (p=0.032). Cold and heat detection thresholds were impaired in this group at the elbow (cold, p=0.034; heat, p=0.010), although only heat detection was impaired at the knee (p=0.009). The moderate-to-severe pain group reported more neuropathic-type pain (p=0.001) as well.
Persistent pain after TKA was associated with widespread pressure, cold hyperalgesia, and a higher amount of neuropathic-type pain.