Absence of improvement with exercise in some patients with knee osteoarthritis: a qualitative study

Key points

1. 01Nonresponders acknowledged their adherence to exercise and physical activity was below target, consistent with quantitative data from the trial.
2. 02Excess body weight was perceived by nonresponders, not responders, as a contributor to poor outcomes; 50% of nonresponders were obese versus 25% of responders.
3. 03Comorbidities (cardiovascular disease, back pain, depression) and life stressors (caring responsibilities, illness of loved ones, moving house, COVID-19) were barriers unique to nonresponders.
4. 04Responders felt empowered to continue or restart exercise independently; this sense of self-efficacy was absent in nonresponders.
5. 05Nonresponders believed standard trial outcome measures (pain and function recall surveys) did not capture improvements they gained in strength, weight loss, or personally meaningful activities.

How it was conducted

Design

Qualitative study nested within a randomized controlled trial; semistructured individual telephone interviews analyzed using reflexive thematic analysis with grounded theory principles

Participants

26 adults with knee osteoarthritis (12 responders, 14 nonresponders); mean age 57 years for responders and 67 years for nonresponders

Responder definition

Improved on both pain and physical function (global rating of change) at 3 months and maintained at 9 months; nonresponders were not improved on both at both time points

Intervention

5 individual consultations over 3 months with a physical therapist (in person or videoconferencing); individualized strengthening program plus physical activity plan with wearable step tracker

Analysis

Inductive thematic analysis within each subgroup; deductive comparison across subgroups; triangulated with quantitative RCT data (BMI, adherence logs)

What they found

• 12 of 16 invited responders and 14 of 24 invited nonresponders completed interviews (26 total).
• At 3 months, half of nonresponders self-reported fewer than the prescribed 3 exercise sessions per week, compared with only 1 responder.
• 7 of 12 responders (58%) reported reduced exercise adherence at 9 months despite initial good adherence.
• 50% of nonresponders (7 of 14) were classified as obese versus 25% of responders (3 of 12).
• Almost all participants attended 100% of physical therapist consultations, except 1 responder and 1 nonresponder (each attending 4 of 5).

Limitations

• 14 eligible participants declined or did not respond to the interview invitation; their views may have altered the findings.
• Responder status was based on one specific definition; alternative approaches to classifying responders in OA trials exist and may yield different findings.
• The study was limited to English-speaking participants, so findings cannot be transferred to non-English-speaking populations.
• Qualitative design cannot establish causation; findings are hypothesis-generating and require testing in RCTs evaluating moderators of exercise response.

Why it matters

For patients

Patients who struggle with exercise because of weight, other health problems, or life stress should discuss these barriers openly with their physiotherapist so the program can be adjusted and additional support arranged.

For clinicians

Clinicians should proactively screen for obesity and comorbidities, monitor adherence closely, address pain flares promptly, and consider booster sessions or digital reminders for patients at risk of nonresponse.

For readers

This qualitative study adds depth to the known average benefits of exercise for knee OA by identifying specific, modifiable barriers that distinguish patients who do not improve, pointing toward more personalized exercise management.