Knee osteoarthritis is one of the reasons people want to lose weight rather than a side issue, and STEP 9 is the trial that measured it directly. It randomized 407 people with obesity and moderate knee osteoarthritis two to one to semaglutide 2.4 mg or placebo for 68 weeks, both arms receiving counseling on physical activity and a reduced-calorie diet[1]. The headline number is large. The number that describes the drug is smaller, and it is the one worth carrying into any decision about what to pay for it.
Both arms improved
Mean WOMAC pain score fell by 41.7 points on semaglutide and by 27.5 points on placebo (P < 0.001). The scale runs 0 to 100 with higher scores worse, and mean baseline pain was 70.9. So the placebo arm — which was not an inert arm, since it included diet and activity counseling — accounted for roughly two thirds of the improvement seen on the drug.
The drug’s own contribution is the 14.2-point difference. That is a real and meaningful effect on a 100-point pain scale. It is not 41.7, and a page that quotes 41.7 without its comparator is quoting the trial rather than reporting it.
The weight figures
Body weight fell 13.7 per cent on semaglutide against 3.2 per cent on placebo. Physical function on the SF-36 improved by 12.0 points against 6.5. Serious adverse events were similar between groups, while discontinuation for adverse events ran 6.7 per cent on the drug against 3.0 on placebo, gastrointestinal problems being the most common reason — which matches what the titration literature reports elsewhere.
What it means for a purchase
Two things. The trial used 2.4 mg semaglutide, which is the weight-management dose most compounded sellers titrate toward, so the dose here does transfer in a way the kidney trial’s 1.0 mg does not. And the comparator matters: the trial is evidence for the drug plus diet and activity counseling, not for the drug alone, and almost no telehealth seller includes structured counseling in what it sells.
If pain relief is the reason for starting, that is worth asking a seller about directly. Most publish nothing about what support comes with the prescription, which is the gap we count in the questions they leave open.