Table 4 Central mechanisms of knee OA

Arendt-Nielsen et al., 2010 [5]

Human

Human

Increased central excitability in OA subjects; greater excitability with greater OA pain; lack of correlation between radiographic findings and pain; no discussion of sex differences.

Arendt-Nielsen et al., 2008 [41]

Human

Human

Healthy men show greater decrease in central excitability in response to conditioned pain modulation.

Bajaj et al., 2001 [35]

Human

Human

Hypertonic saline infusion into tibialis anterior shows greater areas of referred pain; no discussion of sex differences.

Baliki et al., 2008 [43]

Human

Human

fMRI shows enhanced activity in thalamus, somatosensory cortex, cingluate cortex, and amygdala in OA patients in response to painful mechanical stimulation; decreased brain activity in response to intra-articular lidocaine.

Ge et al., 2005 [61]

Human

Human

Reduced pain ratings to a second intramuscular injection of glutamate in men compared to women.

Bwilym et al., 2010 [46]

Human

Human

Imaging study shows that atrophy of thalamus in hip OA is reversed by total hip replacement; no sex differences reported.

Gwilym et al., 2009 [48]

Human

Human

Imaging study shows patients with OA have increased activity in brainstem facilitation pathway that is correlated with neuropathic symptoms; no sex differences reported.

Kulkarni et al., 2007 [44]

Human

Human

Reduction in conditioned pain modulation in OA, that is reversed after total joint replacement in pain-free individuals; no sex differences reported.

LeBars et al., 1979 [37]

Rat

Activation of diffuse noxious inhibitory control pathways reduces activity of nociceptive neurons in spinal cord.

Loyd and Murphy, 2006 [62]

Rat

Rat

Review article including 141 references describing sex differences in central pain modulation.

Parks et al., 2011 [45]

Human

Human

fMRI in knee OA shows spontaneous pain activates prefrontal-limbic regions; COX-2 inhibitor decreases spontaneous pain and activity in prefrontal-limbic regions; no sex differences reported.

Sarlani and Greenspan, 2002 [39]

Human

Human

Greater temporal summation to heat and mechanical stimuli in healthy women than men.

Staud et al., 2003 [40]

Human

Human

Conditioned pain modulation is more effective in heathy men than women.

Tousignant-Laflamme and Marchand, 2009 [42]

Human

Menstrual cycle alters conditioned pain modulation in healthy women.

Yarnitsky et al., 2008 [38]

Human

Human

Lower conditioned pain modulation prior to surgery is predictive of postoperative chronic pain.