Limited evidenceJoints & skin

Achyranthes (Niu Xi)

A root used in Chinese formulas for the knees and lower back, almost always as one component of a multi-herb prescription. Nearly all published research is in animals and cells; there are no placebo-controlled human trials of the herb on its own.

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What the science says

Bone loss in animal models Limited evidence
A systematic review and meta-analysis of preclinical studies found that Achyranthes bidentata root extract improved bone density and structural parameters in osteoporotic rats. The finding is consistent across rodent studies but has not been tested in people.
Joint and back complaints Limited evidence
A comprehensive pharmacology review describes anti-inflammatory, analgesic and osteoprotective activity in laboratory models and long traditional use for knee and lumbar pain. The same review notes the absence of well-designed clinical trials of the single herb.
Isolated use versus traditional formulas Limited evidence
In practice the herb is used inside multi-ingredient prescriptions, so even the clinical impressions behind its reputation cannot be attributed to Achyranthes specifically.

Dosage & safety

Studied doseTraditional decoctions use 9–15 g of the dried root per day. Supplement extracts vary widely in concentration and no dose has been established in trials.

SafetyTraditionally contraindicated in pregnancy because of reported uterine-stimulating activity, and generally avoided with heavy menstrual bleeding. Human safety data are sparse. As with other imported herbal materials, check for third-party testing for heavy metals and adulteration. Not a substitute for assessment of persistent joint or back pain.

How to take it

TimingTiming does not matter.

With food?With food, which is gentler on the stomach for a concentrated decoction.

Worth knowingAvoid it entirely if you are pregnant or trying to conceive, given its long-standing traditional contraindication and reported uterine-stimulating activity.

Frequently asked questions

Does achyranthes help knee and back pain?

Achyranthes (Niu Xi) has limited evidence for knee and back pain: a pharmacology review notes long traditional use and laboratory anti-inflammatory activity, but no well-designed clinical trials of the single herb. Persistent joint or back pain still needs proper assessment.

Does achyranthes help osteoporosis?

A meta-analysis of preclinical studies found achyranthes root extract improved bone density in osteoporotic rats, but achyranthes has not been tested for bone loss in people. The evidence is limited to animals.

How much achyranthes root should I take?

Traditional achyranthes decoctions use 9–15 g of dried root per day. Supplement extracts vary widely in concentration and no dose has been established in trials.

Is achyranthes safe in pregnancy?

No, achyranthes is traditionally contraindicated in pregnancy because of reported uterine-stimulating activity, so avoid it if you are pregnant or trying to conceive, and it is generally avoided with heavy menstrual bleeding. Human safety data are sparse, so choose third-party tested products.

Scientific references

Osteoprotective effect of Achyranthes bidentata root extract on osteoporotic rats: a systematic review and meta-analysis
Yang H, Tang R, Wu HL, Li JH, Zhang C — Pharm Biol, 2024
Achyranthis bidentatae radix: A comprehensive review of botany, processing methods, ethnopharmacology, phytochemistry, pharmacology, quality control, toxicity, and pharmacokinetics
Yang Z, Deng B, Song R, Gao C, Sun Y, Zhu T — J Ethnopharmacol, 2026

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Herbal medicines: what the evidence says (335)