Strength training in addition to neuromuscular exercise and education in individuals with knee osteoarthritis: the effects on pain and sensitization

Key points

1. 01Strength training plus neuromuscular exercise reduced pressure pain thresholds significantly more than neuromuscular exercise alone at 12 weeks
2. 02Neuromuscular exercise alone produced greater reductions in knee pain during the last week and during walking at 12 weeks
3. 03No differences were found between groups in temporal summation, conditioned pain modulation, or number of painful body sites
4. 04Both exercise modes produced overall positive effects on pain sensitization and clinical pain comparable to other established treatments for knee osteoarthritis
5. 05The study is the first RCT to directly compare effects of different exercise modes on pain sensitization in knee osteoarthritis

How it was conducted

Design

Secondary analysis of a patient-blinded, parallel-group RCT (ClinicalTrials.gov ID: NCT03215602)

Participants

90 adults with radiographic and symptomatic knee osteoarthritis (Kellgren-Lawrence score 2 or above), not eligible for knee replacement surgery

Groups

ST+NEMEX-EDU (strength training plus neuromuscular exercise and education, n=45) vs NEMEX-EDU (neuromuscular exercise and education only, n=45)

Intervention duration

12 weeks, twice-weekly sessions; strength training added approximately 10 minutes of knee extension and leg-press after the 60-minute neuromuscular session

Primary outcomes (this analysis)

Cuff pressure pain threshold (PPT), tolerance threshold (PTT), temporal summation (TS), conditioned pain modulation (CPM), VAS knee pain, and number of painful body sites

Analysis

Intention-to-treat mixed model repeated measures; outcomes assessed at baseline, 6 weeks, and 12 weeks

What they found

• PPT in the KOA leg at 12 weeks: adjusted mean difference -5.01 kPa (95% CI -8.29 to -1.73), p=0.0028, favoring ST+NEMEX-EDU
• PPT in the KOA leg at 6 weeks: adjusted mean difference -3.98 kPa (95% CI -7.12 to -0.84), p=0.013, favoring ST+NEMEX-EDU
• PTT in the KOA leg at 12 weeks: adjusted mean difference -8.02 kPa (95% CI -12.22 to -3.82), p=0.0002, favoring ST+NEMEX-EDU
• PTT in the KOA leg at 6 weeks: adjusted mean difference -4.63 kPa (95% CI -8.69 to -0.57), p=0.0255, favoring ST+NEMEX-EDU
• VAS mean knee pain during the last week at 12 weeks: adjusted mean difference -8.4 mm (95% CI -16.2 to -0.5), p=0.0364, favoring NEMEX-EDU
• VAS knee pain during function (30 min walk) at 12 weeks: adjusted mean difference -16.0 mm (95% CI -24.8 to -7.3), p=0.0004, favoring NEMEX-EDU
• No significant between-group differences in temporal summation, conditioned pain modulation, or number of painful body sites at 6 or 12 weeks
• Completion rate: 78% (35/45) in ST+NEMEX-EDU vs 93% (42/45) in NEMEX-EDU at 12 weeks
• Only 42% of the strength training group (19 participants) adhered to pre-determined training frequencies and intensities
• Between-group standardized mean difference for PPT favoring ST+NEMEX-EDU was 0.43 at 12 weeks

Limitations

• The study was powered for the primary physical function outcome, not the pain sensitization outcomes reported here, so findings should be interpreted with caution
• No established minimal important difference or minimal detectable change values exist for cuff algometry pain sensitization, making clinical relevance of PPT and PTT differences uncertain
• Only deep pressure stimuli were used; thermal pain measures were not assessed, limiting generalizability
• Adherence to the strength training protocol was poor, with only 42% of participants meeting pre-specified frequency and intensity targets, which may have attenuated the true effect of strength training

Why it matters

For patients

People with knee osteoarthritis not yet ready for surgery may get better relief from day-to-day knee pain by doing neuromuscular exercise and education without adding high-intensity strength training, even though strength training may reduce some aspects of pain sensitization.

For clinicians

The trade-off between improved pressure pain thresholds with strength training and better clinical pain relief with neuromuscular exercise alone warrants caution before routinely adding high-volume strength training to neuromuscular programs in this population, particularly given low adherence rates observed.

For readers

This is the first RCT directly comparing exercise modes on pain sensitization in knee osteoarthritis; the contrasting direction of effects on experimental versus clinical pain highlights that reducing pain sensitization does not necessarily translate into better self-reported pain outcomes.