{"schemaVersion":1,"id":"en-mechanism-cartilage","type":"mechanism","pillar":"body","locale":"en","translationGroupId":"mechanism-cartilage","slugPath":"body/cartilage","title":"Cartilage","shortTitle":"Cartilage","summary":"The surface two bones glide on. No vessels, no nerves, fed by movement itself — and absent from every scene, as six joint pages already point out.","level":"intermediate","estimatedMinutes":8,"synonyms":["cartilage","articular cartilage","fibrocartilage","chondrocyte","synovial fluid","osteoarthritis"],"blocks":[{"id":"b1","type":"heading","level":2,"text":"The tissue the models never show","anchor":"the-tissue-the-models-never-show"},{"id":"b2","type":"paragraph","content":[{"kind":"text","value":"Each of Body Lab's six joint pages carries the same limitation: \"the cartilage is not represented\". They say so because its absence changes what you see — without it, two bones appear to touch directly, and the fit looks more abrupt than it is."}]},{"id":"b3","type":"paragraph","content":[{"kind":"text","value":"This page describes the missing tissue. It completes "},{"kind":"link","value":"bone","href":"/en/body/bone","external":false},{"kind":"text","value":", the "},{"kind":"link","value":"tendon","href":"/en/body/the-tendon","external":false},{"kind":"text","value":" and "},{"kind":"link","value":"fascia","href":"/en/body/fascia","external":false},{"kind":"text","value":"."}]},{"id":"b4","type":"heading","level":2,"text":"A surface made to glide","anchor":"a-surface-made-to-glide"},{"id":"b5","type":"paragraph","content":[{"kind":"text","value":"Articular cartilage covers the ends of bones with a layer a few millimetres thick. Its function comes down to two words: glide and cushion."}]},{"id":"b6","type":"definition","term":"Articular cartilage","definition":"The smooth, pearly white tissue covering the surfaces of a mobile joint. It is made largely of water, a collagen network, and molecules that hold that water in place.","alsoKnownAs":["hyaline cartilage"]},{"id":"b7","type":"paragraph","content":[{"kind":"text","value":"The coefficient of friction between two lubricated cartilage surfaces is among the lowest known, lower than ice on ice. That quality is the first thing lost when the tissue degrades."}]},{"id":"b8","type":"heading","level":2,"text":"How it feeds itself","anchor":"how-it-feeds-itself"},{"id":"b9","type":"paragraph","content":[{"kind":"text","value":"Here cartilage differs from every other tissue described on this site."}]},{"id":"b10","type":"paragraph","content":[{"kind":"strong","value":"It has no vessels and no nerves."},{"kind":"text","value":" No blood reaches it. Its cells — chondrocytes — are fed by diffusion from the synovial fluid bathing the joint."}]},{"id":"b11","type":"paragraph","content":[{"kind":"text","value":"And that diffusion depends on movement. Alternating load compresses the cartilage, drives out some of the fluid, then lets it soak back in on release. The tissue works like a sponge: it is the load–unload cycle that circulates what it lives on."}]},{"id":"b12","type":"evidence","level":"established","statement":"Articular cartilage has no vessels and no nerves, and feeds by diffusion from the synovial fluid.","detail":"Descriptive anatomy and kinesiology describe the same organisation. It is that lack of blood supply which explains both why a cartilage lesion is not painful in itself, and why its repair is limited.","referenceIds":["standring2020","neumann2016"]},{"id":"b13","type":"heading","level":2,"text":"Why it repairs badly","anchor":"why-it-repairs-badly"},{"id":"b14","type":"paragraph","content":[{"kind":"text","value":"Two consequences follow directly from the absence of vessels."}]},{"id":"b15","type":"paragraph","content":[{"kind":"text","value":"First: a cartilage lesion causes no pain coming from the cartilage itself, since it has no nerve endings. Pain, when it exists, comes from neighbouring structures — the bone beneath, the capsule, the synovial membrane."}]},{"id":"b16","type":"paragraph","content":[{"kind":"text","value":"Second: repair is slow and incomplete. Repair cells arrive by blood, and there is none. The tissue filling a lesion does not have the mechanical properties of the original cartilage."}]},{"id":"b17","type":"comparison","title":"Three tissues, three repair capacities","columns":["Tissue","Blood supply","Repair"],"rows":[{"label":"Bone","cells":["Rich","Complete, with properties restored"]},{"label":"Tendon","cells":["Poor","Slow, often with different tissue"]},{"label":"Articular cartilage","cells":["None","Very limited"]}]},{"id":"b18","type":"heading","level":2,"text":"Two cartilages not to confuse","anchor":"two-cartilages-not-to-confuse"},{"id":"b19","type":"paragraph","content":[{"kind":"text","value":"Articular cartilage is not the only one in the body. The "},{"kind":"strong","value":"menisci"},{"kind":"text","value":" of the "},{"kind":"link","value":"knee","href":"/en/body/joints/knee","external":false},{"kind":"text","value":", the "},{"kind":"strong","value":"labrum"},{"kind":"text","value":" of the "},{"kind":"link","value":"shoulder","href":"/en/body/joints/shoulder","external":false},{"kind":"text","value":" and the "},{"kind":"link","value":"hip","href":"/en/body/joints/hip","external":false},{"kind":"text","value":", and the ring of the "},{"kind":"link","value":"intervertebral discs","href":"/en/body/joints/lumbar-spine","external":false},{"kind":"text","value":" are made of fibrocartilage: richer in collagen, more resistant to tension, less smooth."}]},{"id":"b20","type":"paragraph","content":[{"kind":"text","value":"The distinction matters: fibrocartilage absorbs and spreads, articular cartilage lets things glide. They face different stresses and have different properties."}]},{"id":"b21","type":"heading","level":2,"text":"What its absence from the models implies","anchor":"what-its-absence-from-the-models-implies"},{"id":"b22","type":"callout","tone":"limit","title":"A missing layer, everywhere","content":[[{"kind":"text","value":"No Body Lab scene shows cartilage, for want of a separate mesh in the sources used. That has one constant visual consequence: in the models, bony surfaces appear to meet directly."}],[{"kind":"text","value":"On the pages for the "},{"kind":"link","value":"knee","href":"/en/body/joints/knee","external":false},{"kind":"text","value":", the "},{"kind":"link","value":"hip","href":"/en/body/joints/hip","external":false},{"kind":"text","value":" and the "},{"kind":"link","value":"shoulder","href":"/en/body/joints/shoulder","external":false},{"kind":"text","value":", the gap between two bones is therefore sharper than it really is. The menisci, by contrast, are properly represented — because they exist as distinct parts in the sources, which surface cartilage does not."}]]},{"id":"b23","type":"heading","level":2,"text":"A subject that calls for care","anchor":"a-subject-that-calls-for-care"},{"id":"b24","type":"callout","tone":"caution","title":"What this page does not say","content":[[{"kind":"text","value":"Osteoarthritis is a frequent clinical subject with many and debated causes, and cartilage occupies a central place in common discussion of it. Describing the tissue establishes neither the causes of that condition, nor its diagnosis, nor what to do about it."}],[{"kind":"text","value":"Body Lab proposes here no exercise, no supplement and no loading rule. Persistent joint pain, swelling, or prolonged morning stiffness belong to a health professional."}]]},{"id":"b25","type":"heading","level":2,"text":"Sources","anchor":"sources"},{"id":"b26","type":"sourceList","title":"Main sources","referenceIds":["standring2020","neumann2016"]},{"id":"b27","type":"shapierAction","actionId":"exercises-squat","label":"See the squat exercise","description":"Find the squat exercise sheet in Shapier, a basic exercise that works the quadriceps.","webTarget":"https://shapier.app/en/exercises/squat","appTarget":"shapier://exercises/squat"},{"id":"b28","type":"quiz","title":"Check my understanding","questions":[{"id":"q1","prompt":"Why does a cartilage lesion cause no pain coming from the cartilage itself?","choices":[{"id":"q1c1","label":"Because cartilage has no nerve endings; pain, when it exists, comes from neighbouring structures","correct":true,"explanation":"As the page explains, without nerves the tissue cannot signal its own lesion, and pain comes from the underlying bone, the capsule or the synovial membrane."},{"id":"q1c2","label":"Because synovial fluid numbs the joint","correct":false,"explanation":"Plausible since this fluid bathes the joint, but the page gives it a nutritional role, not an anaesthetic one; it is the absence of nerves that explains the absence of pain."},{"id":"q1c3","label":"Because cartilage is too thin to hurt","correct":false,"explanation":"Its few-millimetre thickness is not what matters: the page ties the absence of pain to the absence of nerve endings."}]},{"id":"q2","prompt":"How is articular cartilage fed?","choices":[{"id":"q2c1","label":"By diffusion from the synovial fluid, through the alternating load–unload cycle","correct":true,"explanation":"With no vessels, its cells are fed by that fluid, and the page compares the tissue to a sponge that loading squeezes and release lets soak back in."},{"id":"q2c2","label":"By blood, like every other tissue","correct":false,"explanation":"That is how bone works, with its rich blood supply, but cartilage has no vessels at all, which is also why its repair is very limited."},{"id":"q2c3","label":"By the collagen it is made of","correct":false,"explanation":"The collagen network structures the tissue and holds water, but the page gives it no role in supplying nutrients."}]},{"id":"q3","prompt":"What distinguishes the menisci from articular cartilage?","choices":[{"id":"q3c1","label":"They are made of fibrocartilage, built to absorb and spread, while articular cartilage lets surfaces glide","correct":true,"explanation":"The page contrasts the two tissues: fibrocartilage is richer in collagen and more resistant to tension, articular cartilage is a gliding surface."},{"id":"q3c2","label":"Nothing, they are two names for the same tissue","correct":false,"explanation":"Plausible since both are found in the knee, but the page says explicitly that these two cartilages must not be confused."},{"id":"q3c3","label":"The menisci are vascularised, articular cartilage is not","correct":false,"explanation":"The page says nothing about the blood supply of the menisci; the distinction it draws concerns the composition and function of the two tissues."}]}]},{"id":"b29","type":"relatedContent","title":"Read next","targetIds":["en-mechanism-bone","en-anatomy-knee-joint","en-anatomy-tendon"]}],"relations":[{"type":"prerequisite","targetId":"en-mechanism-bone"},{"type":"explains","targetId":"en-anatomy-knee-joint"},{"type":"uses-structure","targetId":"en-anatomy-shoulder-joint"},{"type":"next-step","targetId":"en-mechanism-range-of-motion"}],"authors":["equipe-editoriale-shapier"],"reviewers":["Thanh Chau"],"references":[{"id":"standring2020","authors":"Standring S","year":2020,"title":"Gray's Anatomy: The Anatomical Basis of Clinical Practice, 42nd edition","source":"Elsevier","kind":"book","url":"https://shop.elsevier.com/books/grays-anatomy/standring/978-0-7020-7705-0"},{"id":"neumann2016","authors":"Neumann DA","year":2016,"title":"Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation, 3rd edition","source":"Elsevier","kind":"book","url":"https://shop.elsevier.com/books/kinesiology-of-the-musculoskeletal-system/neumann/978-0-323-28753-1"}],"review":{"publishedAt":"2026-08-02","reviewedAt":"2026-08-02","reviewDueAt":"2027-08-02","evidenceLevel":"established"},"limitations":["No scene shows cartilage: the anatomical sources used contain no separate mesh for it. The six joint pages each point this out on their own.","The repair capacities described apply to adult articular cartilage; they differ in children and by site.","Osteoarthritis is a clinical subject with many causes. This page describes a tissue: it establishes neither its causes, nor its diagnosis, nor what to do about it.","Persistent joint pain, swelling, or prolonged morning stiffness belong to a health professional."],"seo":{"title":"Cartilage — the gliding surface, and why it repairs badly","description":"Composition and nutrition of articular cartilage, the role of synovial fluid, how it differs from the fibrocartilage of the menisci, and the limits of its repair.","canonicalPath":"/en/body/cartilage","image":"/og/en/mechanism-cartilage.png"},"app":{"offlineEligible":true},"version":1}