Does Clinically Important Change in Function After Knee Replacement Guarantee Good Absolute Function? The Multicenter Osteoarthritis Study

Abstract

Objective Poor functional outcomes post knee replacement are common, but estimates of its prevalence vary, likely in part because of differences in methods used to assess function. The agreement between improvement in function and absolute good levels of function after knee replacement has not been evaluated. We evaluated the attainment of improvement in function and absolute good function after total knee replacement (TKR) and the agreement between these measures. Methods Using data from The Multicenter Osteoarthritis (MOST) Study, we determined the prevalence of achieving a minimal clinically important improvement (MCII, ≥ 14.2/68 point improvement) and Patient Acceptable Symptom State (PASS, ≤ 22/68 post-TKR score) on the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Physical Function subscale at least 6 months after knee replacement. We also assessed the frequency of co-occurrence of the 2 outcomes, and the prevalence according to pre-knee replacement functional status. Results We included 228 subjects who had a knee replacement during followup (mean age 65 yrs, mean body mass index 33.4,73% female). Seventy-one percent attained the PASS for function after knee replacement, while only 44% attained the MCII. Of the subjects who met the MCII, 93% also attained the PASS; however, of subjects who did not meet the MCII, 54% still achieved a PASS. Baseline functional status was associated with attainment of each MCII and PASS. Conclusion There was only partial overlap between attainment of a good level of function and actually improving by an acceptable amount. Subjects were more likely to attain an acceptable level of function than to achieve a clinically important amount of improvement post knee replacement.

Determinants of Disability in Rheumatoid Arthritis: A Community-Based Cohort Study

“…This study utilizes a HAQ defined patient acceptable state which has been used by other studies to assess outcomes with importance identified by patients with RA [ 33 ]. Further, this technique to generate the patient acceptable state has been expanded upon in other disease such as systemic lupus erythematosus and osteoarthritis [ 34 , 35 ].…”

Concordance between important change and acceptable symptom state following knee arthroplasty: the role of baseline scores

“…Group means may be similar but there may be substantial discordance between PASS and MCID at the level of the individual. Maxwell and colleagues, on the other hand, reported a third of patients undergoing total knee arthroplasty (TKA) were discordant on PASS and MCID estimates 4 . A limitation of the approach by Maxwell and colleagues is that baseline score was not adjusted for in the analysis.…”

Post‐Acute Rehabilitation After Total Knee Replacement: A Multicenter Randomized Clinical Trial Comparing Long‐Term Outcomes

“…In the first instance, this cohort achieved, 12 months after surgery, operated knee pain and activity limitations scores comparable to age‐matched Australian normative data . Furthermore, a total of 304 of the 354 participants (86%) completing the 6‐month WOMAC questionnaire achieved a “participant acceptable symptom state” for activity limitations (≤22 of 68) , a much higher prevalence than the 71% reported in a recent observational study . It is therefore likely that a ceiling effect in these self‐report measures for this cohort restricted the ability to detect any differential effect of the 2 rehabilitation strategies evaluated.…”

“…However, a recent systematic review of longitudinal observational studies revealed that approximately 15% of patients report ongoing moderate‐to‐severe pain in the operated knee for many years after surgery . Further, for self‐reported physical function (or activity limitations), it has been demonstrated that approximately 25% of patients fail to achieve a “patient acceptable symptom state” or a minimum clinically important improvement in function 6 or more months after TKR , and 20% of patients still report moderate‐to‐severe activity limitations 2 years after TKR .…”