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Pain and hyperalgesia in osteoarthritis of the hands.

OBJECTIVE
Tissue damage and pain can lead to a change in the stimulus/response characteristics of the nociceptive system. Hyperalgesia has been described in experimental pain states and some clinical conditions, but has not been investigated in osteoarthritis (OA). We sought to establish the presence of hyperalgesia at the thumb in subjects with OA of the hand and to explore any relationship between sensitivity to extrinsic stimuli and the experience of clinical pain.


METHODS
Subjects with OA of the hand were divided into groups according to their pain profile. The sample also included pain-free OA cases and pain-free controls. Intensity ratings were obtained for each of 3 types of pain: continuous pain, incident pain, and movement pain. Thermal and mechanical detection and pain thresholds were measured over the forearm and the carpometacarpal joint of the thumb.


RESULTS
Lower thermal and mechanical pain thresholds were evident over the thumb relative to forearm in the groups with persistent pain. Subjects complaining only of incident pain, pain-free OA cases, and pain-free controls did not exhibit regional differences in sensitivity to thermal and mechanical stimuli. Increased ratings of continuous pain were associated with lower thermal and mechanical pain thresholds. Variance in movement pain ratings was predicted by mechanical forearm pain thresholds.


CONCLUSION
OA in the hands is associated with cutaneous and deep hyperalgesia to thermal and mechanical stimuli. Increased levels of continuous pain are associated with more pronounced hyperalgesia. The associations of movement pain suggest the contribution of central mechanisms in the stimulus/response changes accompanying movement pain.