Stemmer's sign is one of the simplest tests in medicine: try to pinch and lift a fold of skin at the base of the second toe (or middle finger, for arms). If the skin is too thickened to lift into a fold, the sign is positive — and that points towards lymphoedema, because protein-rich lymph fluid gradually thickens the skin and tissue in a way other swelling doesn't.
Its value lies in what it separates. Venous swelling and lipoedema generally leave that skin fold liftable — so a positive Stemmer's helps distinguish lymphoedema from its two most common lookalikes, right at the foot where lymphoedema (unlike lipoedema) shows up. A negative sign doesn't fully rule lymphoedema out, especially early — it's a strong clue, not a verdict.
You can try it yourself before an appointment; better, mention it there: "my Stemmer's sign seems positive" is the kind of specific observation that moves a consultation forward. Pair it with the pitting test.