This study provides moderate-level evidence for pain catastrophizing as an independent predictor of chronic pain post-TKA .
BACKGROUND Total knee arthroplasty ( TKA ) is a common and costly surgical procedure .
Despite high success rates , many TKA patients develop chronic pain  in the months and years following surgery , constituting a public health burden .
Pain catastrophizing is a construct that reflects anxious preoccupation with pain , inability to inhibit pain-related fears , amplification of the significance of pain vis-à-vis health implication s , and a sense of helplessness regarding pain .
Recent research suggests that it may be an important risk factor for untoward TKA outcomes .
To clarify this impact , we systematic ally review ed the literature to date on pain catastrophizing as a prospect i ve predictor of chronic pain following TKA .
Clinical importance of changes in chronic pain intensity measured on an 11-point numerical pain rating scale
& NA ;  Pain intensity is frequently measured on an 11‐point pain intensity numerical rating scale ( PI‐NRS ) , where 0=no pain and 10=worst possible pain . However , it is difficult to interpret the clinical importance of changes from baseline on this scale ( such as a 1‐ or 2‐point change ) . To date , there are no data driven estimates for clinical ly important differences in pain intensity scales used for chronic pain studies . We have estimated a clinical ly important difference on this scale by relating it to global assessment s of change in multiple studies of chronic pain . Data on 2724 subjects from 10 recently completed placebo‐controlled clinical trials of pregabalin in diabetic neuropathy , postherpetic neuralgia , chronic low back pain , fibromyalgia , and osteoarthritis were used . The studies had similar design s and measurement instruments , including the PI‐NRS , collected in a daily diary , and the st and ard seven‐point patient global impression of change ( PGIC ) , collected at the endpoint . The changes in the PI‐NRS from baseline to the endpoint were compared to the PGIC for each subject . Categories of ‘ much improved ’ and ‘ very much improved ’ were used as determinants of a clinical ly important difference and the relationship to the PI‐NRS was explored using graphs , box plots , and sensitivity/specificity analyses . A consistent relationship between the change in PI‐NRS and the PGIC was demonstrated regardless of study , disease type , age , sex , study result , or treatment group . On average , a reduction of approximately two points or a reduction of approximately 30 % in the PI‐NRS represented a clinical ly important difference . The relationship between percent change and the PGIC was also consistent regardless of baseline pain , while higher baseline scores required larger raw changes to represent a clinical ly important difference . The application of these results to future studies may provide a st and ard definition of clinical ly important improvement in clinical trials of chronic pain therapies . Use of a st and ard outcome across chronic pain studies would greatly enhance the comparability , validity , and clinical applicability of these studies
This study provides moderate-level evidence for pain catastrophizing as an independent predictor of chronic pain post-TKA .
BACKGROUND Total knee arthroplasty ( TKA ) is a common and costly surgical procedure .
Despite high success rates , many TKA patients develop chronic pain  in the months and years following surgery , constituting a public health burden .
Pain catastrophizing is a construct that reflects anxious preoccupation with pain , inability to inhibit pain-related fears , amplification of the significance of pain vis-à-vis health implication s , and a sense of helplessness regarding pain .
Recent research suggests that it may be an important risk factor for untoward TKA outcomes .
To clarify this impact , we systematic ally review ed the literature to date on pain catastrophizing as a prospect i ve predictor of chronic pain following TKA .