Xi Yan Calf's Nose, Eyes of the Knee

What does Xi Yan do?

Xi Yan is a purely local point — everything documented about it concerns the knee it sits on, and nothing else. It is an extra point, belonging to no channel, so it carries no channel-theory action; what the reference literature records is a knee point used directly at the joint for pain, swelling, stiffness and difficulty bending and straightening. Its whole clinical identity is that it reaches the front of the knee joint from the two soft hollows either side of the patellar ligament, where little more than a thin layer of tissue separates the needle from the joint itself.

• Relieves knee pain — the defining documented use, and the reason the point exists. It is used for pain at the front of the knee in particular.
• Reduces local swelling of the knee — recorded across the reference literature; the hollows in which the point sits are precisely the places that fill and flatten when the joint swells, which is why they are palpated as well as needled.
• Improves bending and straightening of the knee — the texts record it where movement is restricted and guarded, not only where the joint is painful at rest.
• Addresses weakness and heaviness of the leg — a secondary documented use, generally where weakness accompanies a painful knee rather than as a complaint on its own.
• Used as a pair, and needled from one side through to the other — the through-needling technique from one hollow to the other, behind the patellar ligament, is documented specifically at this point and is the most distinctive thing recorded about it.

A correction worth stating plainly. Our own earlier record described Xi Yan as "dispelling wind-damp", "moving qi and blood in the knee joint" and serving as "a primary local point for knee bi (painful obstruction)". Those are channel and pathogen-theory phrases, and Xi Yan lies on no channel — it has no five-shu, yuan, luo, xi-cleft, back-shu or front-mu classification, and no channel passes through it that could be moved or freed. The points at the knee that genuinely carry that reasoning are all held here: ST-35 Du Bi, the Stomach channel point occupying the lateral hollow, whose recorded actions are exactly to dispel wind-damp, reduce swelling and activate the channel; GB-34 Yang Ling Quan, the He-Sea point of the Gallbladder channel and the influential point of the sinews, which is the point for the tendons and ligaments of the body; SP-09 Yin Ling Quan, the He-Sea point of the Spleen channel and the principal point for resolving dampness; and ST-34 Liang Qiu, the Xi-Cleft point of the Stomach channel and therefore the channel point for an acute, painful, swollen knee. What the sources actually document at Xi Yan is a local effect at a joint, arrived at empirically, and that is what is set out above.

Source: Sacred Lotus sources & references (existing action and indication record, corrected as described; ST-34, ST-35, SP-09 and GB-34 records); Deadman & Al-Khafaji, A Manual of Acupuncture, extra points (p. 583); Chinese Acupuncture & Moxibustion (p. 252); cross-referenced against multiple online sources.

What is Xi Yan used for?

Xi Yan is used for the knee, and for very little else. The indications carried in Sacred Lotus sources & references are knee pain and weakness of the lower extremities, and the wider reference literature adds only closely related presentations of the same joint. This is an unusually short indication list, and keeping it short is the accurate thing to do.

• Knee pain, particularly at the front of the joint
• Knee osteoarthritis — by far the commonest modern application, and the condition in which the point has actually been used in studies
• Swelling of the knee joint
• Stiffness of the knee, with restricted bending and straightening
• Knee injury and post-traumatic knee pain
• Weakness of the leg and lower limb accompanying a painful knee
• Numbness and motor impairment around the knee

What it is not used for. The reference literature does not record Xi Yan for systemic complaints, for internal organ disorders, or for any presentation away from the knee. Where a knee problem is one part of a wider pattern — damp accumulation, weakness of the sinews, deficiency affecting the legs — the point that carries that reasoning is on a channel: SP-09 Yin Ling Quan for damp, GB-34 Yang Ling Quan for the sinews, BL-23 Shen Shu and KI-03 Tai Xi for the deeper deficiency to which weak knees are traditionally attributed. Xi Yan's contribution is the local one, and it is used alongside those rather than in place of them.

Source: Sacred Lotus sources & references (existing indication record; SP-09, GB-34, BL-23 and KI-03 records); Deadman & Al-Khafaji, A Manual of Acupuncture, extra points (p. 583); Chinese Acupuncture & Moxibustion (p. 252); cross-referenced against multiple online sources.

Where is Xi Yan, and is the lateral one really ST-35?

Yes — and this is the single most useful thing to know about this point, because it is stated wrongly more often than it is stated correctly. Xi Yan is a pair of points, one either side of the patellar ligament, and the lateral member of that pair occupies the same location as ST-35 Du Bi, a channel point held separately in this library. The medial member is the extra point proper. We queried our own records to confirm this rather than working from recall: our ST-35 record locates it "in the hollow formed when the knee is flexed, immediately below the patella and lateral to the patellar ligament", while our Xi Yan record locates the pair "in the hollows formed when the knee is flexed, immediately below the patella and both medial and lateral to the patellar ligament". The lateral hollow is therefore described twice, under two names.

In our own words the anatomy is simple. Bend the knee and the patellar ligament — the strong cord running from the kneecap down to the shin bone — stands out, with a soft dimple on either side of it. Those two dimples are the "eyes of the knee". The outer one is ST-35 Du Bi. The inner one is the true extra point, distinguished in many sources as Nei Xi Yan ("Medial Xi Yan"); Sacred Lotus sources & references hold no separate Nei Xi Yan record, treating the pair under this one entry. When a source says "Xi Yan", it usually means both together.

The naming and coding of this point are genuinely inconsistent in the published literature, and pretending otherwise would be misleading. The clinical research itself shows the confusion plainly. One trial of knee osteoarthritis lists "Dubi (ST 35)" and "Xiyan (EX-LE 4)" as two separate points in the same prescription (Zhongguo Zhen Jiu 2014;34(4):329–33, PMID 24946628). A moxibustion trial lists "Xiyan (EX-LE5)" and "Dubi (ST35)" as two separate points (Zhen Ci Yan Jiu 2024;49(2):171–6, PMID 38413038), as does an experimental study in mice (J Pain Res 2022;15:1071–82, PMID 35444462). A third trial simply writes "Xiyan (ST 35)", treating the two names as one point (Zhen Ci Yan Jiu 2015;40(4):300–3, PMID 26502544). So the same word appears coded EX-LE 4, EX-LE 5 and ST-35 across four studies of the same condition, and our own needling record carries the older code MN-LE-16. Sacred Lotus sources & references keep our location for both records unchanged and record the collision rather than picking a winner. The practical rule for a reader: if a source names both Xiyan and Dubi, it means the medial hollow and the lateral hollow; if it names only Xiyan, it almost certainly means both.

How is Xi Yan used in practice?

As a pair, at a flexed and supported knee, and very often needled from one hollow through to the other. The knee is bent — the reference literature describes a rolled support beneath it — because the hollows only open when the joint is flexed; with the leg straight there is nothing to needle into. Three approaches are recorded: straight in towards the back of the knee, obliquely upward and inward behind the kneecap, and through-needling from the lateral hollow to the medial one behind the patellar ligament. The last of these is the technique most associated with the point.

Which points is Xi Yan combined with?

• With ST-35 Du Bi — inevitably, since one member of the pair is ST-35. Naming both is the conventional way of indicating that both hollows are used.
• With He Ding — "Crane's Summit", the extra point in the depression at the middle of the top edge of the kneecap, held here. Xi Yan below and He Ding above bracket the joint, and our He Ding record names Xi Yan as its standard partner.
• With ST-34 Liang Qiu and SP-10 Xue Hai — the two points above the knee, on the outer and inner sides of the thigh respectively. ST-34 is the Xi-Cleft point of the Stomach channel, which makes it the channel choice for an acutely painful, swollen knee; SP-10 sits on the bulge of muscle above the inner knee. Both are held here.
• With GB-34 Yang Ling Quan and SP-09 Yin Ling Quan — the paired He-Sea points below the knee on the outer and inner sides. GB-34 is the influential point of the sinews and the standard addition for any tendon or ligament problem.
• With GB-33 Xi Yang Guan and LIV-08 Qu Quan — the joint-line points on the outer and inner sides of the knee, used where the pain sits at the side rather than at the front.
• With ST-36 Zu San Li — immediately below and lateral to Xi Yan on the Stomach channel; in practice it is nearly always in the same prescription.

A validation study comparing sixteen randomised trials of acupuncture for knee osteoarthritis pain against what acupuncturists actually do found the most frequently used points to be ST-34, ST-35, ST-36, SP-06, SP-09, SP-10, GB-34, Xiyan and Ashi points — a list that matches the combinations above closely, and one of the few published confirmations that trial protocols and real practice broadly agree at this joint (Acupunct Med 2012;30(3):187–94, PMID 22759902).

Source: Sacred Lotus sources & references (existing use record, needling record and location; ST-34, ST-35, ST-36, SP-06, SP-09, SP-10, GB-33, GB-34, LIV-08 and He Ding records, queried directly to confirm the ST-35 relationship and the absence of a separate Nei Xi Yan record); Deadman & Al-Khafaji, A Manual of Acupuncture, extra points (p. 583) and ST-35 (p. 157); Chinese Acupuncture & Moxibustion (pp. 252, 154); PubMed PMID 24946628, 38413038, 35444462, 26502544, 22759902 — each verified resolvable and checked for retraction status before citation; cross-referenced against multiple online sources.

Where is Xi Yan located?

• A Manual of Acupuncture (p. 583): On the knee, in the hollows formed when the knee is flexed, immediately below the patella and both medial and lateral to the patellar ligament.

How is Xi Yan needled in the textbooks?

Reference record only — this describes what the standard texts document, not instruction for a reader. Sacred Lotus sources & references record that the knee is flexed and supported by a rolled pillow, and then set out three documented approaches: perpendicular insertion directed towards Wei Zhong BL-40 behind the knee, 1 to 2 cun; oblique insertion angled medially and upward behind the kneecap, 1 to 2 cun; and through-needling from the lateral to the medial hollow, passing behind the patellar ligament. Our ST-35 record, describing the lateral hollow of the same pair, gives perpendicular insertion of 0.7 to 1.0 inch with moxibustion applicable.

• Position documented: knee flexed and supported. This is not a matter of comfort — the hollows only exist when the joint is bent, and with the leg extended there is no point to locate.
• Angle documented: perpendicular towards the back of the knee; or obliquely, medially and superiorly, behind the patella; or transversely from one hollow to the other.
• Depth documented: 1 to 2 cun in our own record, with the shorter figure of 0.7 to 1.0 inch recorded at ST-35.
• Moxibustion: recorded as applicable, and moxibustion at this point has been used in trials in its own right (Zhen Ci Yan Jiu 2024;49(2):171–6, PMID 38413038).
• Electroacupuncture is commonly recorded, the two hollows of the pair being convenient to connect.

What are the safety considerations at Xi Yan?

Xi Yan carries none of the hazard that governs points over the chest, the upper back or the abdomen — there is no body cavity, no lung and no internal organ anywhere near it. What bounds it instead is the knee joint itself, which lies directly beneath. The point sits in the soft hollow between the patellar ligament and the bone, and the recorded depths of 1 to 2 cun are enough for a needle to enter the joint space. The considerations the reference literature records follow from that, and they are set out here as safety reference rather than as guidance for performing anything.

• The joint capsule and the infrapatellar fat pad lie immediately deep to the point. The fat pad is a well-recognised source of pain in its own right and is sensitive to being disturbed; local soreness after treatment at this point is common and expected.
• Joint infection is the theoretical serious event at any point overlying a synovial joint, and strict clean-needle technique is the standard practice that addresses it. A 2024 review of the acupuncture safety literature lists infections among the small number of genuinely serious adverse events and attributes them to contaminated needles and inadequate skin disinfection rather than to needling as such (Am J Chin Med 2024;52(6):1555–1587, PMID 39460372). A knee that becomes hot, swollen and increasingly painful after any needling requires immediate medical assessment.
• Existing joint disease and joint replacement change what lies beneath the skin. The reference literature treats a prosthetic joint as a reason for particular caution at local points, on infection grounds.
• Bleeding and bruising — the region is vascular, and bruising at the knee is among the commoner minor events after needling anywhere on the limb. Minor bleeding, bruising and residual soreness are the most frequently reported acupuncture adverse events overall (PMID 39460372).
• Risk in proportion. A meta-analysis of prospective clinical studies estimated serious acupuncture-related adverse events at approximately 1 per 10,000 patients and about 8 per million treatments, with roughly half of all recorded events being bleeding, pain or flare at the needle site (Bäumler P et al., BMJ Open 2021;11:e045961, PMID 34489268). The large randomised trial of acupuncture for chronic knee pain described under research reported no serious treatment-related events (JAMA 2014;312(13):1313–22, PMID 25268438).

Standard clean-needle practice applies. Acupuncture is performed by qualified, licensed practitioners; this record documents the literature and is not a technique guide.

Source: Sacred Lotus sources & references (existing needling record; ST-35 needling record); Deadman & Al-Khafaji, A Manual of Acupuncture, extra points (p. 583) and ST-35 (p. 157); Chinese Acupuncture & Moxibustion (pp. 252, 154); PubMed PMID 38413038, 39460372, 34489268, 25268438 — each verified resolvable and checked for retraction status before citation.

What does the name Xi Yan mean?

Xi Yan means "Knee Eyes" — xi is the knee, yan is an eye — and the second name our record carries, "Calf's Nose", belongs properly to its lateral member. The image is exact: bend the knee and look at it, and the two soft hollows either side of the patellar ligament sit like a pair of eyes below the kneecap, with the ligament between them like the bridge of a nose. Straighten the leg and the eyes close. Because the whole complex resembles the muzzle of a calf, the lateral hollow acquired the separate name Du Bi, "Calf's Nose", which is how the Stomach channel point ST-35 is known. Our record carries both names because both are in use for this location; the distinction between them is set out below and under how the point is used.

Is Xi Yan the same point as ST-35 Du Bi?

Partly — and this is the most frequently mis-stated relationship in the extra point repertoire, so it is worth the space. Xi Yan is a pair. Its lateral member occupies the same place as ST-35 Du Bi, a point of the Stomach channel held separately in Sacred Lotus sources & references. Its medial member, often distinguished as Nei Xi Yan ("Medial Xi Yan"), is the extra point proper and has no channel affiliation at all. So the answer to "is Xi Yan ST-35?" is: half of it is.

The practical consequences are worth spelling out:

• The recorded actions differ between the two hollows even though they sit a centimetre or two apart. ST-35, being a channel point, carries channel actions — dispelling wind-damp, reducing swelling, activating the channel and relieving pain. The medial hollow, being an extra point, carries only the local documented use. A reader who wants the channel reasoning should be reading our ST-35 record; a reader who wants the pair as a local treatment should be reading this one.
• Coding is inconsistent in the literature, as set out under uses above: the same name appears as EX-LE 4, as EX-LE 5 and as ST-35 across published trials of the same condition, and our own needling record carries the older code MN-LE-16.
• Neither our Xi Yan location nor our ST-35 location has been altered. They describe overlapping ground because the points overlap; the overlap is documented rather than edited away.

How does Xi Yan compare with He Ding?

He Ding ("Crane's Summit"), also held here, sits in the depression at the middle of the top edge of the kneecap, where Xi Yan sits below it. The two bracket the joint from above and below and are used together as a matter of routine — our He Ding record names Xi Yan first among its partners. Both are extra points, both are purely local, both are chosen for knee pain, swelling and weakness, and neither carries channel actions. The difference is position and nothing else: He Ding approaches the joint from above the kneecap, Xi Yan from below it. Where the knee is diffusely painful both are commonly used at once, often with ST-34 Liang Qiu and SP-10 Xue Hai above and GB-34 Yang Ling Quan and SP-09 Yin Ling Quan below, which is close to the standard local knee prescription in modern practice.

Is Xi Yan a channel point?

No — or, more precisely, not as a pair. Xi Yan is an extra point. Extra points sit outside the fourteen channels: they were recorded for an observed clinical effect rather than derived from channel theory, so they carry no five-shu, yuan, luo, xi-cleft, back-shu or front-mu classification. That is why our record shows no channel and no point categories, and why the actions above are framed as documented local use rather than as channel mechanics. The exception is the overlap already described — the lateral hollow of the pair coincides with ST-35, which is a channel point, and that is precisely why the relationship confuses people.

Is there research on Xi Yan?

There is no research that isolates Xi Yan, and that should be said plainly. What exists is a large literature on acupuncture for knee osteoarthritis in which Xi Yan appears in almost every protocol — which tells you the point is standard, not that the point has been tested. That distinction matters and is easy to lose.

• The point is near-universal in knee protocols. The validation study cited above, assessing sixteen randomised trials against practitioner practice, found the most frequently used points to be ST-34, ST-35, ST-36, SP-06, SP-09, SP-10, GB-34, Xiyan and Ashi points, with only minor differences between research protocols and practice (Acupunct Med 2012;30(3):187–94, PMID 22759902). Xi Yan is in the core set by consensus.
• Trials that include it are protocol trials. A non-randomised concurrent-control trial in 193 patients with knee osteoarthritis used ST-34, ST-35, ST-36, GB-34, SP-09, SP-10, Xiyan and GB-33, reporting better pain and function scores in the immediately-treated group at four weeks with the benefit still present four weeks after treatment ended (Zhongguo Zhen Jiu 2014;34(4):329–33, PMID 24946628). A randomised trial of moxibustion compared a six-point regimen including Xiyan and Dubi against a three-point one (Zhen Ci Yan Jiu 2024;49(2):171–6, PMID 38413038). A four-arm trial combined needling at SP-10, ST-34, GB-34, Xiyan and Ashi points with shock-wave therapy at three frequencies (Zhen Ci Yan Jiu 2015;40(4):300–3, PMID 26502544). In each case the result belongs to the protocol, not to this point.
• Experimental work uses the point in animals. A study in mice with induced knee osteoarthritis applied fire needling at "xiyan" (EX-LE5), "dubi" (ST35), "liangqiu" (ST34) and "xuehai" (SP10), reporting reduced pain behaviour, improved synovial and cartilage findings and a shift in macrophage polarisation (J Pain Res 2022;15:1071–82, PMID 35444462). An unusual application outside treatment used the two Xiyan hollows as a fixed electrode pair for bioimpedance measurement of knee injury, detecting an approximately 5 per cent reduction in knee bioimpedance in injured knees across 76 samples (IEEE Trans Biomed Circuits Syst 2022;16(5):962–971, PMID 35994551) — evidence about the location rather than about needling it, and included here because it is genuinely point-specific.
• What the wider evidence on the knee shows is mixed, and should be represented as such. A meta-analysis of eleven trials found acupuncture gave clinically relevant short-term improvements in pain and function against waiting-list and usual-care controls, but improvements against sham that were statistically real and clinically irrelevant (Ann Intern Med 2007;146(12):868–77, PMID 17577006). A Zelen-design randomised trial in 282 people aged 50 and over with chronic knee pain found neither needle nor laser acupuncture better than sham at twelve weeks, with modest improvements against no treatment that had disappeared at one year (JAMA 2014;312(13):1313–22, PMID 25268438). Against that, an individual patient data meta-analysis of 39 trials and 20,827 patients across four chronic pain conditions including osteoarthritis found acupuncture superior both to sham and to no acupuncture, with effects of roughly 0.5 standard deviations against no-acupuncture control and about 0.2 against sham, declining only about 15 per cent at one year (J Pain 2018;19(5):455–474, PMID 29198932). A network meta-analysis compared seven needling methods for knee osteoarthritis and ranked them against one another, though on total-effective-rate outcomes of limited reliability (Medicine (Baltimore) 2023;102(43):e35670, PMID 37904438).

The fair summary: Xi Yan is a standard, near-universal local knee point whose standing rests on long clinical use and on its inclusion in essentially every protocol studied, not on evidence about the point itself. The honest thing to say is that the knee has been studied a great deal and this point has not been studied in isolation at all.

Source: Sacred Lotus sources & references (name, location and existing use record; ST-34, ST-35, SP-09, SP-10, GB-33, GB-34 and He Ding records); Deadman & Al-Khafaji, A Manual of Acupuncture, extra points (p. 583) and ST-35 (p. 157); Chinese Acupuncture & Moxibustion (pp. 252, 154); PubMed PMID 22759902; 24946628; 38413038; 26502544; 35444462; 35994551; 17577006; 25268438; 29198932; 37904438 — each verified resolvable and checked for retraction status before citation; cross-referenced against multiple online sources.