Could Activity Modifications Indicate Physical Decline Among Adults With Symptomatic Knee Osteoarthritis?

Effect of Context Specificity on Response to the Shortened WOMAC Function Scale in Patients Undergoing Total Knee Arthroplasty

OBJECTIVE

To determine, in patients undergoing total knee arthroplasty (TKA), whether increasing context specificity of selected items of the shortened version of the Western Ontario and McMaster Universities Osteoarthritis Index function (WOMAC-F) scale (ShortMAC-F) (1) enhanced the convergent validity of the ShortMAC-F with performance-based mobility measures (ii) affected mean scale score, structural validity, reliability, and interpretability.

DESIGN

Secondary analysis of randomized clinical trial data.

SETTING

A tertiary teaching hospital.

PARTICIPANTS

Patients undergoing TKA (N=114).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

The ShortMAC-F was modified by specifying the "ascending stairs" and "rising from sitting" items to enquire about difficulty in performing the tasks without reliance on compensatory strategies, whereas the modified "level walking" item enquired about difficulty in walking 400 m. Before and 12 weeks after TKA, patients completed the WOMAC-F questionnaire, modified ShortMAC-F questionnaire, knee pain scale questionnaire, sit-to-stand test, fast gait speed test, and stair climb test. Interpretability was evaluated by calculating anchor-based substantial clinical benefit estimates.

RESULTS

The modified ShortMAC-F correlated significantly more strongly than ShortMAC-F or WOMAC-F with pooled performance measures (differences in correlation values, 0.12-0.14). Increasing item context specificity of the ShortMAC-F did not influence its psychometric properties of unidimensionality (comparative fit and Tucker-Lewis indices, >0.95; root mean square error of approximation, 0.05-0.08), reliability (Cronbach's α, 0.75-0.83), correlation with pain intensity (correlation values, 0.48-0.52), and substantial clinical benefit estimates (16 percentage points); however, it resulted in lower mean score (4.5-4.8 points lower).

CONCLUSIONS

The modified ShortMAC-F showed sufficient measurement properties for clinical application, and it seemed more adept than WOMAC-F at correlating with performance-based measures in TKA.

Defining and Measuring Preclinical Mobility Limitation: An Expert Consensus Exercise Informed by a Scoping Review

BACKGROUND

Early change in function in older adults has been termed preclinical disability (PCD). PCD has been understudied compared to other stages of disability because it is unlikely to receive comparative priority in clinical settings. It has major implications for prevention and population health as it may be the optimal time to intervene to prevent further decline. A standardized approach to research in PCD, including a common definition and measurement approaches, is needed to advance this work.

METHODS

The process to establish how PCD should be defined and measured was undertaken in 2 stages: (1) a scoping review of the literature, which was used to inform (2) a web-enabled consensus meeting with content experts.

RESULTS

The scoping review and the consensus meeting support the use of the term preclinical mobility limitation (PCML) and that it should be measured using both patient-reported and performance-based measures. It was agreed that the definition of PCML should include modification of frequency and/or method of task completion, without overt disability, and that requisite mobility tasks include walking (distance and speed), stairs, and transfers.

CONCLUSIONS

Currently, there are few standardized assessments that can identify PCML. PCML is the term that most clearly describes the stage where people experience a change in routine mobility tasks, without a perception of disability. Further evaluation into the reliability, validity, and responsiveness of outcome measures is needed to advance research on PCML.

Reduction in Thigh Muscle Strength Occurs Concurrently but Does Not Seem to Precede Incident Knee Pain in Women: Data From the Osteoarthritis Initiative Cohort

OBJECTIVE

The aim of the study was to investigate whether muscle strength declines before or concurrent with incident knee pain in subjects with and without radiographic knee osteoarthritis.

DESIGN

Osteoarthritis initiative participants with incident knee pain (occurrence of infrequent/frequent knee pain during the past 12 mos at two consecutive follow-up time points (either years Y3 + Y4 or Y4 + Y5) were compared with controls (no incident knee pain) with 2-yr changes in knee extensor strength during BL➔Y2 (before) and Y2➔Y4 (concurrent).

RESULTS

Two hundred two knees (49% women, 40% radiographic knee osteoarthritis) displayed incident pain, and 439 did not (46% women, 23% radiographic knee osteoarthritis). Women with radiographic knee osteoarthritis displayed a significantly greater (P = 0.04) reduction in knee extensor strength concurrent with incident pain compared with controls (mean = -17.6 N vs. +4.5 N), but men did not. A similar trend was observed in women without radiographic knee osteoarthritis, but this was not statistically significant (P = 0.08). There was no significant relationship with change in extensor strength before incident pain (P ≥ 0.43).

CONCLUSIONS

These results suggest that in women, incident knee pain is accompanied by a concurrent reduction in knee extensor strength, whereas loss in strength does not precede incident knee pain. The findings encourage interventional studies that attempt to attenuate a decline in extensor strength once knee symptoms occur.