Xu Duan (Sichuan Teasel Root, Dipsacus asperoides), also known as Chuan Duan and Chuan Xu Duan, is the dried root of a Dipsacaceae plant. Its name — xu (continue, mend) and duan (broken, severed) — directly describes its defining clinical action: continuing what is broken, mending what is severed. Its TCM character: bitter-pungent, slightly warm; enters Liver and Kidney channels. Bitter drains and descends; pungent disperses and activates; the slight warmth supplements and warms. This combination produces the classical description: “supplements without stagnating, activates without injuring” — a rare Liver-Kidney dual tonic that simultaneously moves Blood and unblocks channels. The Shen Nong Ben Cao Jing classifies it as an upper-class drug: “governs injury from Cold, supplements insufficiency, treats metal-wound carbuncle-ulceration, mends sinew and bone.” The Ben Cao Gang Mu summarises: “supplements Liver-Kidney, continues sinew-bone, regulates Blood vessels, specially treats lumbar-back aching pain, weak and powerless foot-knee, foetal leakage-slip, falls and sprains.” Its four core clinical territories: (1) Liver-Kidney deficiency with lumbar-knee weakness; (2) traumatic injuries, fractures, and sinew-bone damage; (3) gynaecological Blood-vessel regulation and foetal stabilisation; (4) Wind-Damp bi-syndrome with Cold-Damp channel obstruction.

I. Classical Records and TCM Properties

Four classical benchmarks:

• Shen Nong Ben Cao Jing (upper-class): governs injury from Cold; supplements insufficiency; treats metal-wounds, carbuncle-ulceration, falls and sprains; mends sinew and bone
• Ming Yi Bie Lu: stops pain and promotes muscle growth; treats female metrorrhagia and leucorrhoea — adding the gynaecological dimension
• Ben Cao Gang Mu: Li Shizhen’s summary: “supplements Liver-Kidney, continues sinew-bone, regulates Blood vessels, specially treats lumbar-back aching pain, weak and powerless foot-knee, foetal leakage-slip, falls and sprains”
• Dian Nan Ben Cao: strengthens sinew and bone, walks through channels and collaterals, stops sinew-bone pain, activates the whole body’s Qi and Blood

TCM properties: Bitter, pungent, slightly warm; enters Liver and Kidney channels. “Bitter drains and descends, pungent disperses and activates, warm supplements and warms.” This three-quality combination is the pharmacological basis for Xu Duan’s “supplement without stagnating, activate without injuring” character — it both nourishes Liver-Kidney Essence and simultaneously moves the Blood and unblocks the channels, preventing the cloying stagnation that pure tonic herbs can produce.

Regional origin and processing: Sichuan production (Chuan Xu Duan) is considered the highest quality. Harvest: autumn, excavate roots, remove rootlets and earth, gentle-fire dry to half-dry, pile and “sweat” (fa han), then sun-dry completely. Three processing forms with different functional emphasis:

• Raw (sheng yong): strongest Blood-activating, trauma-treating, and channel-unblocking action
• Salt-processed (yan xu duan): guided to the Kidney channel; stronger Liver-Kidney supplementation and lumbar-knee strengthening
• Wine-processed (jiu xu duan): enhanced Blood-activating and channel-unblocking; stronger for traumatic injury and bi-syndrome pain

Appearance: Cylindrical shape; surface grey-brown with longitudinal wrinkles and horizontal-elongated lenticels; firm and solid; cross-section cortex black-green, wood yellow-brown; faint aroma; bitter and mildly sweet taste.

II. Four Core Actions

1. Supplement Liver-Kidney and strengthen sinew-bone: Xu Duan nourishes the Liver-Kidney Essence and Blood that, when deficient, fail to maintain the health of sinew (governed by Liver) and bone (governed by Kidney). Clinical pattern: lumbar and knee aching and pain, weakness and lack of strength in the lower limbs, heavy and powerless legs, dizziness and tinnitus — the classic deficiency triad of chronic constitutionally exhausted individuals: the middle-aged and elderly, those with overwork depletion, and post-partum women. The salt-processed form (Yan Xu Duan) is preferred for this application as salt guides the formula to the Kidney channel.

2. Continue fractures and heal injuries — activate Blood and relieve pain: This is the action that gave the herb its name. Xu Duan promotes the regeneration and healing of bone and sinew tissue after fracture and injury. It activates Blood and disperses Stasis (the pungent quality), reduces swelling and relieves pain, and accelerates structural tissue repair. The raw or wine-processed form is preferred. Indicated for: traumatic injury with swelling and pain, fracture recovery, sinew-vessel contusion, and Blood-Stasis internal blockage pain. Modern pharmacology confirms Xu Duan alkaloids promote osteoblast proliferation and bone mineralisation — a direct molecular basis for this classical action.

3. Regulate Blood vessels and stabilise the foetus — gu chong an tai: Xu Duan regulates the Chong (Penetrating) and Ren (Conception) Vessels, which govern female reproductive function. This produces two related gynaecological actions:

• Stop metrorrhagia and regulate menstruation: Liver-Kidney deficiency with failure to contain the Chong-Ren — prolonged menstrual dripping-and-lingering (beng lou), excessive menstrual flow, post-partum lochia not stopping; pair with Dang Gui, Shu Di, Ai Ye, E Jiao, Huang Qi
• Stabilise the foetus: Kidney-deficiency failure to hold and stabilise the foetus — foetal restlessness (tai dong bu an), foetal leakage and haemorrhage (tai lou), habitual miscarriage; the classical Shou Tai Wan formula (Xu Duan + Sang Ji Sheng + E Jiao + Tu Si Zi + Bai Zhu + Huang Qin)

4. Dispel Wind-Damp and stop bi-syndrome pain: Xu Duan’s pungent-warm quality disperses the Cold-Damp that has invaded the channels. Addresses Wind-Damp bi-syndrome with joint aching and pain, restricted flexion-extension, cold aching lumbar and legs, limb numbness. Used alongside Du Huo, Fang Feng, Qin Jiao, Gui Zhi, Niu Xi, and Du Zhong.

III. Five Classical Formulas

1. Xu Duan Du Zhong Tang (Zheng Zhi Zhun Sheng)
Composition: Xu Duan 12g · Du Zhong 12g · Niu Xi 10g · Gou Qi Zi 10g · Shu Di 15g · Dang Gui 10g · Bai Shao 10g · Rou Gui 3g (add last). Action: supplement Liver-Kidney, strengthen sinew-bone, warm and unblock channels. Indication: Liver-Kidney deficiency — cold lumbar-knee aching and pain, weak and powerless lower limbs, dizziness and tinnitus, cold aversion. Xu Duan activates Blood while supplementing; Du Zhong provides stronger warm-supplementation; Niu Xi guides downward to lower limbs; Shu Di and Dang Gui nourish Blood; Rou Gui warms Yang.

2. Shou Tai Wan (Yi Xue Zhong Zhong Can Xi Lu)
Composition: Xu Duan 10g · Sang Ji Sheng 12g · E Jiao 10g (dissolved separately) · Tu Si Zi 15g · Bai Zhu 10g · Huang Qin 6g. Action: nourish Blood and stabilise the foetus, supplement Kidney and settle foetal restlessness. Indication: Liver-Kidney deficiency and Qi-Blood insufficiency — foetal restlessness, foetal leakage haemorrhage, habitual miscarriage; also relieves pregnancy lumbar aching and small-abdominal downward pressure. A historically important formula for threatened miscarriage.

3. Xu Gu Huo Xue Tang (Zhong Yi Shang Ke Xue)
Composition: Xu Duan 12g · Gu Sui Bu 10g · Dang Gui 10g · Hong Hua 6g · Tao Ren 6g · Ru Xiang 6g · Mo Yao 6g · Zi Ran Tong 10g (calcined) · Niu Xi 10g. Action: activate Blood and disperse Stasis, continue sinew and join bone, reduce swelling and relieve pain. Indication: traumatic injury, Blood-Stasis swelling and pain, fracture and sinew injury (acute phase and recovery). Xu Duan here coordinates the supplementing action with multiple Blood-activating herbs, providing the sinew-bone structural support while Zi Ran Tong, Gu Sui Bu, and Ru Xiang-Mo Yao address the injury directly.

4. Xu Duan Gu Chong Tang (experiential formula)
Composition: Xu Duan 12g · Dang Gui 10g · Shu Di 15g · Bai Shao 10g · Huang Qi 15g · Bai Zhu 10g · E Jiao 10g (dissolved) · Ai Ye 6g. Action: nourish Blood and regulate Chong-Ren vessels, stop haemorrhage. Indication: female Qi-Blood deficiency with Chong-Ren failure to contain — metrorrhagia (prolonged menstrual dripping), excessive menstruation, post-partum lochia not stopping; with pale complexion, fatigue, and shortness of breath.

5. Xu Duan Qu Feng Shi Tang (experiential formula)
Composition: Xu Duan 12g · Du Huo 10g · Fang Feng 10g · Qin Jiao 10g · Gui Zhi 6g · Niu Xi 10g · Du Zhong 10g. Action: dispel Wind-Damp, strengthen sinew-bone, stop bi-syndrome pain. Indication: Wind-Damp bi-syndrome, restricted joint flexion-extension, cold lumbar-leg aching and pain, limb numbness. Suitable for middle-aged and elderly Wind-Damp bone disease and post-partum Wind-Damp.

IV. Two-Herb Differential: Xu Duan vs Du Zhong; Xu Duan vs Gu Sui Bu

V. Modern Pharmacology

Core chemical constituents: Xu Duan saponins (xu duan zao gan), volatile oils, alkaloids, multiple amino acids, and triterpenoid saponins.

Documented pharmacological actions:

• Bone tissue repair and fracture healing: promotes osteoblast proliferation; accelerates bone mineralisation; directly supports the classical “continue sinew and join bone” action
• Anti-inflammatory and analgesic: inhibits inflammatory mediators; reduces bone-joint inflammation pain; adjunctive in osteoarthritis and rheumatoid arthritis
• Female endocrine regulation: improves Blood circulation; regulates female hormonal function; adjunctive in gynaecological deficiency disorders
• Immune enhancement and anti-fatigue: enhances immune function; reduces physical fatigue
• Sedative and anxiolytic: mild CNS sedation; improves constitutional fatigue and weakness

Modern applications: Bone-joint supplement products; middle-aged and elderly lumbar-knee health maintenance; traumatic injury recovery and rehabilitation; female gynaecological deficiency adjustment; post-partum recovery. Key ingredient in Qiang Gu Jiao Nang, Xu Duan Zhuang Gu Pian, and An Tai Wan patent formulas.

VI. Dosage and Safety

Dosage: decoction 9–15g daily; dietary preparation (bone-broth soup with pork ribs or chicken): 5–10g; pill or powder: appropriate amount. Salt-processed or wine-processed form selected based on clinical need and medical guidance.

Suitable populations: Liver-Kidney deficiency with lumbar-knee aching; sinew-bone weakness and powerlessness; traumatic injury; foetal restlessness; constitutional Blood-Stasis; middle-aged and elderly, post-partum women, prolonged sedentary workers.

Contraindications:

• Acute excess-Heat Blood-Stasis (acute traumatic injury with active red-swollen-hot-pain, inflammation not yet resolved): supplementing too early may lock in Heat; address inflammation first, then supplement
• Active exterior febrile illness: stop supplementation during fever, sore throat, and yellow phlegm; resume after recovery
• Yin deficiency-Fire prominent (tidal flushing, night sweats, dry mouth, red tongue): Xu Duan’s slight warmth may worsen Heat; use with caution or combine with Yin-nourishing herbs
• Qi stagnation-Phlegm-Damp (abdominal distension, thick greasy coating): use with caution
• Pregnancy antenatal care: must be used under medical supervision with appropriate formula; do not self-administer large amounts
• Fracture patients: combine with appropriate external injury management; do not rely solely on herbal treatment
• Avoid combining with: spicy-hot foods, peppercorns, hot-natured meats (lamb) for prolonged periods to prevent worsening internal Heat