【方歌】下石疽在膝上生，坚硬如石牵筋疼，皮色如常难溃敛，
证由血滞外寒凝。
【注】此证生于膝间，无论膝盖及左右，俱可以生。坚硬如石
，牵筋疼痛，肿如鸡卵，皮色不变，并无焮热，难消难
溃，既溃难敛，最属疲顽。由身虚寒邪深袭，致令血瘀
凝结而成肿溃。内外治法，俱与中石疽参考。但此证肿
溃俱凉，若凉化为热，见诸善证者始吉；仍见恶证者，
难痊。
【方歌】缓疽血滞外寒凝，肿硬如馒膝上生，紫黯溃迟多焮热，
肿久渐腐烂皮疼。
【注】此证由外寒深袭，血瘀凝滞而成。生于两膝上，或生于
膝两旁，肿硬如馒，木痛日增，其色紫黯，积日不溃，
证之情形，与下石疽相似，惟多焮热，肿久则腐烂肌肉
、皮肤。初服当归拈痛汤，以宣通湿热，次按中石疽治
法，内宜温补，外宜灸法。虚甚者十全大补汤相兼治之
。
又方：当归拈痛汤（见股部腿游风）
十全大补汤（见溃疡门）委中毒
【方歌】委中毒在腘纹生，屈伸本硬微肿红，胆热流入膀胱遏，
速宜活血刺委中。
【注】此证生委中穴，穴在膝后腘中央约纹，动脉陷中即是。
约纹者，折纹也，又名血郗，穴属膀胱经，俗名腿凹，
经曰腘中。由胆经积热，流入膀胱，壅遏不行而成。木
硬肿痛、微红、屈伸艰难。治宜速用活血散瘀汤，逐下
恶血为效，缓则筋缩而成废疾！诸书皆云：兼刺委中穴
出血自消。然刺穴必兼有腰痛不能转移者，方可刺之，
即出血亦不可过多，多则令人身扑，面见脱色。其余内
外治法，俱按痈疽肿疡、溃疡门。亦有焮痛、色赤、溃
速者，由湿热凝结所致，治法亦按肿疡、溃疡门。
方剂：活血散瘀汤
组成：当归尾 赤芍
桃仁（去皮、尖） 大黄（酒炒，各二钱）
川芎 苏木（各一钱五分）
丹皮 枳壳（麸炒）
栝蒌仁（各一钱） 槟榔（六分）
水二钟，煎八分，空心服；渣，再煎服。
【方歌】活血散瘀委中毒，皆因积热肿其处，归芍丹皮桃枳榔，
栝蒌大黄芎苏木。
【方歌】下石疽生于膝盖上方，肿块坚硬如石头，牵引筋脉疼痛，皮肤颜色正常，难以溃破和愈合。此证由血行滞涩、外感寒邪凝结所致。
【注】此病证发生在膝部中间，无论是膝盖正中和左右两侧，都可以发生。肿块坚硬如石，牵引筋脉疼痛，肿胀像鸡蛋大小，皮肤颜色不变，没有红肿发热，难以消散，难以溃破，即使溃破也难以收敛，属于顽固难治之症。这是由于身体虚弱，寒邪深入侵袭，导致血液瘀结凝聚而形成肿溃。内治和外治的方法，都参照中石疽的疗法。但是此证在肿胀和溃破时都是凉的，如果凉性转化为热性，出现各种顺证（善证）才是吉兆；如果仍然出现逆证（恶证），则难以痊愈。
【方歌】缓疽因血行滞涩、外感寒邪凝结，肿胀坚硬像馒头一样生在膝盖上方，颜色紫暗，溃破迟缓且多有红肿发热，肿胀日久逐渐腐烂，皮肤疼痛。
【注】此证由外感寒邪深入侵袭，导致血液瘀滞凝结而成。生于两膝上方，或生于膝盖两旁，肿胀坚硬像馒头，麻木疼痛日益加重，颜色紫暗，多日不溃破。病情情形与下石疽相似，只是多了红肿发热，肿胀日久则肌肉和皮肤腐烂。初期服用当归拈痛汤，以宣通湿热，随后按照中石疽的治疗方法，内服宜温补，外用宜灸法。虚损严重的，配合使用十全大补汤治疗。
又一方：当归拈痛汤（见股部腿游风章节）
十全大补汤（见溃疡门章节）
委中毒
【方歌】委中毒生于腘窝横纹处，屈伸时原本僵硬，轻微肿胀发红，因胆经热邪流入膀胱经受阻，应迅速采用活血疗法并针刺委中穴。
【注】此病证生于委中穴，该穴位位于膝盖后方腘窝中央的横纹处，动脉凹陷之中即是。约纹即折纹，又名血郗，该穴属于膀胱经，俗称腿凹，经典中称为腘中。由于胆经积热，流入膀胱经，壅塞阻滞不通而形成。表现为木硬肿痛、微红、屈伸困难。治疗应迅速使用活血散瘀汤，驱逐下部的恶血以见效，若延误则会导致筋脉收缩而成废疾！各类医书都说：兼刺委中穴出血即可自行消除。然而针刺穴位必须兼有腰痛不能转动的症状，才可以针刺，即使出血也不可过多，过多会导致人跌倒，面色苍白脱色。其余内外治疗方法，都按照痈疽肿疡、溃疡门的法则处理。也有红肿疼痛、颜色赤红、溃破迅速的，这是由湿热凝结所致，治疗方法也按肿疡、溃疡门处理。
方剂：活血散瘀汤
组成：当归尾 赤芍
桃仁（去皮、尖） 大黄（酒炒，各二钱）
川芎 苏木（各一钱五分）
丹皮 枳壳（麸炒）
栝蒌仁（各一钱） 槟榔（六分）
水两钟，煎至八分，空腹服用；药渣再煎服用。
【方歌】活血散瘀汤治委中毒，皆因积热使患处肿胀，方中含归尾、芍药、丹皮、桃仁、枳壳、槟榔、栝蒌、大黄、川芎、苏木。
[Prescription Verse] Xiashiju (Lower Hard Scrofula) arises above the knee, hard as stone with tendon-pulling pain, skin color remains normal, difficult to ulcerate and heal. This syndrome is caused by blood stasis and external cold coagulation.
[Note] This condition occurs in the knee area; it can arise at the kneecap itself or on either side. The mass is hard as stone, causing tendon-pulling pain, swelling like a chicken egg, with unchanged skin color, no erythema or heat, difficult to dissipate, difficult to ulcerate, and once ulcerated, difficult to granulate and close. It is most stubborn and persistent. It results from body deficiency and deep invasion of cold pathogens, leading to blood stasis and coagulation forming the swelling and ulceration. Internal and external treatments refer to Zhongshiju (Middle Hard Scrofula). However, since this condition presents as cool during both swelling and ulceration phases, if the coolness transforms into heat and favorable signs appear, it is auspicious; if unfavorable signs persist, recovery is difficult.
[Prescription Verse] Huanju (Slow Abscess) involves blood stasis and external cold coagulation, swelling and hardness like a steamed bun arising above the knee, purple-dark discoloration, delayed ulceration often accompanied by erythema and heat, prolonged swelling gradually leads to rotting flesh and painful skin.
[Note] This condition is caused by deep invasion of external cold, resulting in blood stasis and stagnation. It arises above both knees or on either side, swelling and hardening like a steamed bun, with increasing numbness and pain, purple-dark color, and failure to ulcerate after many days. The clinical presentation is similar to Xiashiju, but distinguished by the presence of erythema and heat; prolonged swelling causes rotting of muscle and skin. Initially, administer Danggui Nian Tong Tang (Angelica Decoction for Relieving Pain) to diffuse and unblock damp-heat. Subsequently, treat according to Zhongshiju methods: internally use warming tonification, externally apply moxibustion. For severe deficiency, combine with Shiquan Dabu Tang (Ten Substance Great Tonifying Decoction).
Another prescription: Danggui Nian Tong Tang (see section on Leg Roaming Wind in the Thigh); Shiquan Dabu Tang (see section on Ulcers).
Wei Zhong Du (Abscess at Weizhong)
[Prescription Verse] Wei Zhong Du arises at the popliteal crease, stiffness upon flexion and extension with slight swelling and redness, due to Gallbladder heat flowing into the Bladder meridian and being obstructed; promptly employ blood-invigorating therapy and puncture Weizhong.
[Note] This condition arises at the Weizhong acupoint, located in the depression of the central artery at the popliteal crease behind the knee. The crease is also called Xuexi (Blood Pool), belonging to the Bladder Meridian, commonly known as the leg hollow, and referred to as Guzhong (Center of the Popliteal Fossa) in classics. It is formed by accumulated heat in the Gallbladder meridian flowing into the Bladder meridian, causing congestion and obstruction. Symptoms include woody hardness, swelling, pain, slight redness, and difficulty in flexion and extension. Treatment should promptly utilize Huoxue Sanyu Tang (Blood Invigorating and Stasis Dispelling Decoction) to purge inferior evil blood for effect; delay will lead to tendon contraction and disability! All texts state that puncturing Weizhong to bleed will cause spontaneous resolution. However, puncture is only indicated when accompanied by low back pain preventing movement. Even then, bleeding must not be excessive, as too much may cause fainting and pallor. Remaining internal and external treatments follow the protocols for Tumors/Abscesses (Yong Ju) in their early swelling stage (Swelling Ulcer) and late ulceration stage (Ulcer). Cases with intense pain, bright red color, and rapid ulceration are caused by damp-heat coagulation; treatment also follows the Swelling Ulcer and Ulcer sections.
Prescription: Huoxue Sanyu Tang
Composition: Dangguiwei (Caulis Angelicae Sinensis Caudex), Chishao (Radix Paeoniae Rubra), Taoren (Semen Persicae, peeled and de-husked), Dahuang (Radix et Rhizoma Rhei, wine-fried, each 2 qian), Chuanxiong (Rhizoma Chuanxiong), Sumu (Lignum Sappan, each 1.5 qian), Danpi (Cortex Moutan), Zhike (Pericarpium Citri Reticulatae, bran-fried), Gualouren (Semen Benincasae, each 1 qian), Binglang (Areca Seed, 0.6 qian).
Decoct in two zhong of water until one-eighth remains; take on an empty stomach; decoct the dregs again and take.
[Prescription Verse] Huoxue Sanyu Tang treats Wei Zhong Du, all due to accumulated heat causing swelling at the site; it contains Dangguiwei, Shaoyao, Mudanpi, Taoren, Zhike, Binglang, Gualou, Dahuang, Chuanxiong, and Sumu.