Research Summary

Evaluation of clinically relevant states in patient reported outcomes in knee and hip osteoarthritis: The patient acceptable symptom state

Tubach, F., Ravaud, P., Baron, G., Falissard, B., Logeart, I., Bellamy, N. (2005) Ann. Rheum. Dis. 64(1): 34–7.

Key Findings


Knee OA patients consider themselves pain-free when they report VAS scores of 32.3 mm or lower.


Knee OA patients consider themselves well overall at VAS scores of 31.0 mm or lower.


Knee OA patients consider their knee function sufficient at WOMAC scores of 31.0 or lower.

A prospective cohort study used three patient reported outcomes typical in trials for osteoarthritis (OA) to estimate the patient acceptable symptom state (PASS), which is the value at which patients consider themselves well. Participants included 1362 outpatients with knee or hip OA who reported a minimum VAS pain score at the beginning of the study and required treatment with a non-steroidal anti-inflammatory drug (NSAID). At a baseline visit and a visit four weeks after starting NSAID treatment, participants reported on their pain, global assessment of disease activity, and functional impairment. At their final visit, patients also reported whether they found their current state satisfactory.

For each of the outcome measures, PASS estimates were stratified into a low, intermediate, or high group based on the patients’ initial scores. For knee OA, patients in the intermediate grouping considered themselves pain-free if they scored below 32.3 on the 0–100 mm visual analog scale (VAS). For other outcomes, PASS scores and their 95% confidence intervals are reported in Table 3. PASS estimates did not vary across age, sex, or duration of disease.

Relevance to Spring Loaded Braces

The PASS can help researchers interpret results of their clinical trials. In a retrospective pilot survey on the Spring Loaded knee brace 1– Budarick, A.R. et al. (2020) J. Prosthet. Orthot. Under Peer Review., PASS estimates provided by Tubach et al. (2005) were used to evaluate patients’ 0-100 mm VAS scores. In the trial, a group of 40 adults with knee pain characteristic of tibiofemoral, patellofemoral, or multi-compartment knee OA wore a Spring Loaded brace for one month and reported on several patient outcomes, including pain levels, at the end of the period. For all OA types, patients reported VAS scores below the minimum PASS estimate, indicating the efficacy of Spring Loaded bracing in reducing pain to satisfactory levels.

Multiple Forces Reduced

Each TCO brace model significantly reduced PF, TF, PC ligament, PT and QT forces during a deep knee bend test.

Reduced Joint Load

Each TCO brace model significantly reduced knee joint loads by at least 32% when compared to the non-braced condition.

Replicates & Extends Previous Research

Results corroborate the knee joint offloading capabilities of a TCO, as demonstrated in a previous study (Budarick et al. 2020).

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