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Why doesn't knee cartilage grow back?

What is inside a knee?

Femur Cartilage Meniscus Tibia Fluidin the capsule Bone underthe cartilage Close up 2 to 4 mm cartilage, then bone (Fox et al., 2009) Weight of fresh cartilage Water: up to 80% Rest: collagen, aggrecan Collagen Type II: 90 to 95% (Fox et al., 2009) Menisci seen from above Red: edge with blood supply 10 à 25 % In the cartilage Blood vessels: 0 Lymphatics: 0 Nerves: 0 Synovial fluid It gets in by diffusion Under the cartilage Cartilage Tidemark Calcified Bone, marrow and vessels
Blood vesselsCartilageJoint fluid

Simplified front cross-section; the cartilage and the space between the bones are enlarged so they can be seen. Tap a label to go to its step.

The steps as text, and where these numbers come from
    With care: this page explains; it does not replace medical advice. A knee that swells, locks, gives way, or hurts for weeks deserves a doctor's opinion.

    Frequently asked questions about knee cartilage

    Can knee cartilage regenerate?

    Very little. Its collagen, built around age 12, is barely renewed in adults, and an injury that stays within the cartilage does not heal on its own (Heinemeier et al., 2016; Hunziker, 1999). When the injury reaches the bone, scar tissue fills the hole, but it is a less sturdy fibrocartilage (Armiento et al., 2019).

    Does cartilage have nerves?

    No. It has no nerves, no blood vessels, and no lymphatic vessels (Fox et al., 2009). That is also why it heals poorly: no vessel brings it what it needs for repair.

    Does walking wear down cartilage?

    What is measured is a temporary squeeze: kneecap cartilage lost 2.8% of its volume after a walk, while some of its water left (Eckstein et al., 2005). At rest, the fluid comes back (Fox et al., 2009). This back-and-forth mostly helps large molecules; glucose and oxygen arrive mostly by diffusion (O'Hara et al., 1990).

    Do glucosamine and chondroitin make cartilage grow back?

    Trials do not show it. In 10 pooled trials with 3,803 people with hip or knee osteoarthritis, the space between the bones on X-rays barely changed compared with placebo, and the drop in pain stayed below the threshold for a noticeable effect (Wandel et al., 2010).

    How many people have knee osteoarthritis?

    Worldwide, about 16% of people aged 15 and over and 22.9% of those aged 40 and over, or about 654 million people aged 40 and over in 2020 (Cui et al., 2020). It becomes more common with age: in the Framingham study, about 27% of people aged 63 to 69 and 44% of those aged 80 and over had signs of knee osteoarthritis on X-rays (Felson et al., 1987).

    See also

    Do gelatin or collagen help repair tendons? How long does it take for a broken bone to heal? Why do bones become fragile with age?

    Sources

    1. Fox AJS, Bedi A, Rodeo SA. The Basic Science of Articular Cartilage: Structure, Composition, and Function. Sports Health, 2009. doi:10.1177/1941738109350438
    2. Heinemeier KM et al. Radiocarbon dating reveals minimal collagen turnover in both healthy and osteoarthritic human cartilage. Science Translational Medicine, 2016. doi:10.1126/scitranslmed.aad8335
    3. Jørgensen AEM et al. Collagen Growth Pattern in Human Articular Cartilage of the Knee. Cartilage, 2021. doi:10.1177/1947603520971016
    4. Verzijl N et al. Effect of collagen turnover on the accumulation of advanced glycation end products. Journal of Biological Chemistry, 2000. doi:10.1074/jbc.M006700200
    5. Hunziker EB. Articular cartilage repair: are the intrinsic biological constraints undermining this process insuperable? Osteoarthritis and Cartilage, 1999. doi:10.1053/joca.1998.0159
    6. Armiento AR, Alini M, Stoddart MJ. Articular fibrocartilage: Why does hyaline cartilage fail to repair? Advanced Drug Delivery Reviews, 2019. doi:10.1016/j.addr.2018.12.015
    7. Gomoll AH et al. The subchondral bone in articular cartilage repair: current problems in the surgical management. Knee Surgery, Sports Traumatology, Arthroscopy, 2010. doi:10.1007/s00167-010-1072-x
    8. Arnoczky SP, Warren RF. Microvasculature of the human meniscus. American Journal of Sports Medicine, 1982. doi:10.1177/036354658201000205
    9. Eckstein F et al. In vivo cartilage deformation after different types of activity and its dependence on physical training status. Annals of the Rheumatic Diseases, 2005. doi:10.1136/ard.2004.022400
    10. O'Hara BP, Urban JP, Maroudas A. Influence of cyclic loading on the nutrition of articular cartilage. Annals of the Rheumatic Diseases, 1990. doi:10.1136/ard.49.7.536
    11. Cui A et al. Global, regional prevalence, incidence and risk factors of knee osteoarthritis in population-based studies. EClinicalMedicine, 2020. doi:10.1016/j.eclinm.2020.100587
    12. Felson DT et al. The prevalence of knee osteoarthritis in the elderly. The Framingham Osteoarthritis Study. Arthritis and Rheumatism, 1987. doi:10.1002/art.1780300811
    13. Wandel S et al. Effects of glucosamine, chondroitin, or placebo in patients with osteoarthritis of hip or knee: network meta-analysis. BMJ, 2010. doi:10.1136/bmj.c4675
    14. GBD 2021 Osteoarthritis Collaborators. Global, regional, and national burden of osteoarthritis, 1990 to 2020 and projections to 2050. Lancet Rheumatology, 2023. doi:10.1016/S2665-9913(23)00163-7

    True or false?

    Cartilage collagen renews itself as fast as skin collagen.

    False. It would take about 117 years to replace half the cartilage collagen, compared with 15 years for skin collagen (Verzijl et al., 2000).

    Cartilage is fed by the joint fluid.

    True. With no blood vessels, it gets its nutrients from the synovial fluid, by diffusion (Fox et al., 2009).

    An injury that reaches the bone heals with identical cartilage.

    False. The hole fills with fibrocartilage, made of type I and II collagen, less sturdy than the original cartilage (Armiento et al., 2019; Gomoll et al., 2010).

    Cite this page

    To cite this page in a paper, an article or a presentation:

    Metabolive. "Why doesn't knee cartilage grow back?" Updated November 2, 2026. https://metabolive.com/en/bones-kidneys/knee-cartilage.