High-intensity laser beat ultrasound as an exercise adjunct in knee osteoarthritis, by a very large margin

Design

single-centre, assessor-blinded randomised controlled trial, both arms receiving exercise

Population

66 adults with knee osteoarthritis, randomised 1:1, treated twice weekly for six weeks

Primary outcome

WOMAC total score change from baseline to 12 weeks after treatment

Effect

-40.0 points with laser against -8.2 with ultrasound; adjusted difference -27.7 (95% CI -39.0 to -16.5, P<0.001) against a minimum important change of 10

Therapeutic ultrasound is offered for knee osteoarthritis in a great many physiotherapy departments on thin evidence. This single-centre, assessor-blinded trial randomised 66 adults with knee osteoarthritis to high-intensity laser therapy or ultrasound, twice weekly for six weeks, both as adjuncts to exercise, with WOMAC total score change at 12 weeks after treatment as the primary outcome.

The difference was large. WOMAC fell by a mean 40.0 points with laser against 8.2 with ultrasound, an adjusted between-group difference of -27.7 points (95% CI -39.0 to -16.5, P<0.001) against a minimum important change taken as 10 points. Secondary outcomes - visual analogue pain, Oxford Knee Score, KOOS and EQ-5D-5L - all favoured laser in exploratory analysis. The laser group held its gains to 12 weeks after treatment ended, while the ultrasound group lost theirs gradually.

A between-group difference of nearly three times the minimum important change, in a 66-patient single-centre trial, should prompt caution rather than enthusiasm. Effects this large are unusual in osteoarthritis and often shrink substantially in multicentre replication; patients were not blinded, and high-intensity laser is a visibly different experience from ultrasound, which matters for a self-reported primary outcome. The more secure conclusion is about the comparator: the ultrasound arm improved by 8.2 points on WOMAC, below the minimum important change, in patients who were also exercising. That is a reasonable prompt to ask what therapeutic ultrasound is contributing in your own department.

• Question the routine use of therapeutic ultrasound in knee osteoarthritis - the comparator arm here did not reach the minimum important change
• Do not purchase high-intensity laser equipment on a 66-patient single-centre trial
• Keep exercise as the core intervention; both arms received it, and it is what the evidence base rests on
• Note patients could not be blinded to which device they received, and the primary outcome was self-reported
• Watch for multicentre replication before treating this effect size as real

Why it matters

It puts a number on how little the ultrasound machine in the physiotherapy department is adding.

Don't overread it

Sixty-six patients at one centre, unblinded to the intervention, with a self-reported primary outcome and an implausibly large effect.

The statistics, in plain English

An adjusted between-group difference of 27.7 WOMAC points against a minimum important change of 10 is nearly three times the threshold, which in a field where most interventions struggle to clear it once is a reason for scepticism rather than excitement. With 33 patients per arm, the confidence interval is wide (-39.0 to -16.5) and the point estimate unstable. Patients knew which treatment they were receiving, and WOMAC is entirely self-reported - the combination reliably inflates effect sizes.

Read the rest in the app

You have read your two free briefings this month. The app carries all 27 specialties, every morning, free — and this finding is waiting in it.

Get Daily Doctor — free

Scan to keep reading on your phone. No account needed to start.