Tendons, Ligaments, and Cartilage A Primer

Tendons are strong, flexible cords of tissues that connect muscles to bones. When we contract our muscles, tendons pull the attached bone, and they can absorb some impact from muscle movement.1,2 Ligaments are bands of tissue that connect and stabilize bones, joints, and organs. Ligaments are responsible for preventing the dislocation of bones and twisting of joints.1,3 Cartilage is a flexible connective tissue that surrounds the ends of bones and cushions joints. Cartilage acts as a shock absorber to reduce stress on bones and joints, reduces friction between bones, and supports the structure of joints.4 All three of these tissues are crucial components for the movement and structure of the body.

Tendons

Tendons are composed of collagen fibers arranged in bundles. They are stiffer than muscles, have greater tensile strength, and can withstand heavy loads with minimal deformations. For example, the flexor tendons in the foot can support over eight times one’s body weight. Tendons vary in size based on their attached muscles. Typically, wide and short tendons are attached to muscles that generate large amounts of force, having greater tensile strength than thinner and longer tendons, which are attached to muscles responsible for more delicate and less forceful movements. Some tendons are surrounded by tendon sheaths that are responsible for producing synovial fluid, which lubricates the area and allows the tendon to move smoothly. Tendons attach to muscles and bones at the muscle-tendon junction and osteo-tendinous junction, respectively.2,5

With age, tendons weaken and become more susceptible to injury. Loss of estrogen in female individuals loosens tendons, thus making them more susceptible to injury and inflammation.5

Strains, one of the most common tendon injuries, occur when a tendon is overstretched, torn, or twisted, typically due to repetitive movements or physical activity. Strains often occur in the arms, legs, feet, and back.1,2 Another common tendon injury is tendinitis, which happens as a result of inflammation of the tendon. Overuse, repetitive movements, and aging can cause tendinitis. Common areas affected by tendinitis include rotator cuff, elbow, wrist, knee, and ankle.2,6 A combination of tendinitis and inflammation of the tendon sheath is called tenosynovitis, commonly affecting the fingers.2 These issues of the tendon can be treated with rest, ice, compression, and elevation (RICE), as well as anti-inflammatory medications. In certain cases, tendinitis and tenosynovitis may require surgical care.1,2,6

Ligaments

Similar to tendons, ligaments are made of collagen bundles. These strong bands of flexible tissue connect to most bones in the body, limiting the amount of movement between bones.3,7 Ligaments can stabilize organs as well. For instance, ligaments connect the liver, stomach, and intestine and hold them in place, and they stabilize the uterus in the pelvis.3

Ligament sprains occur when the tissue is overstretched or torn. Sprains commonly occur in the wrist, ankle, or knee, and are often caused by sudden impacts, falls, or twists. Pain, swelling, difficulty bearing weight, and looseness in the affected area are symptoms of sprains.1,3,7 Ligament sprains are divided into three grades. Grade 1 sprains are mild, typically healing within six weeks. These can be treated with RICE and antiinflammatory medications. Grade 2 sprains involve a partial tear, with increased difficulty bearing weight and using the affected body part compared to a Grade 1 sprain. Using a brace or another supportive device is often recommended to avoid stretching the ligament. Grade 2 sprains often take 6 to 12 weeks to heal. Grade 3 sprains involve complete tear or rupture, accompanied by severe pain, bruising, and swelling. Avoiding stress from weight bearing is crucial for proper healing, and in some cases, surgery is necessary to repair the ligament. These injuries can take several months, or even a year or more, to fully heal.3,7

Cartilage

Cartilage is a flexible, nonvascular connective tissue composed of collagen and elastic fibers that comes in three forms. The most common type, hyaline cartilage, lines joints and the ends of bones. Its slippery, smooth surface allows for frictionless movement and prevents bones from rubbing against each other. Hyaline cartilage is located in the nasal passages, between the ribs and sternum, and at the ends of bines that form joints. Fibrocartilage is the toughest and least flexible type, and it provides support and rigidity in the body. Fibrocartilage can be found between spinal vertebrae, in the knee joint, and at the junction where tendons attach to bones. The most flexible type of cartilage is elastic cartilage. This cartilage provide support and maintains shape in areas such as the external ears, Eustachian tubes, and larynx.4,8

Osteoarthritis involves the breakdown of cartilage in the joints, leading to pain and inflammation. Herniated disks occur when cartilage between the vertebrae is torn or punctured.4,8 Injuries, such as meniscal tears or a separated shoulder, can tear or damage cartilage in the joints.4 Additionally, forceful or small and repetitive impacts and twisting the joint when it is bearing weight can damage cartilage. Cartilage injuries occur most frequently in the knee, but other common areas of injury include the shoulder, ankle, and hip.9

NUTRITION FOR HEALTH TENDONS, LIGAMENTS, AND CARTILAGE

Vitamin C contributes to collagen synthesis, with vitamin C deficiency leading to collagen loss;10–12 as tendons and ligaments are composed of cartilage, sufficient vitamin C consumption is crucial. Supplementing vitamin C with gelatin10,11,13 or collagen10,11 has potential to treat tendon and ligament injuries, though further research is needed to verify this finding. Citrus fruits, red bell peppers, strawberries, broccoli, and kiwis are good sources of vitamin C.11,12

Emerging evidence suggests that the intake of hydrolized collagen supplements, in combination with other therapies, might reduce pain related to tendon injuries.11,14,15

However, more high-quality studies are needed to confirm these claims.

Vitamin D and K deficiencies are associated with cartilage damage and osteoarthritis. Foods high in vitamin K include broccoli, Brussels sprouts, and leafy greens.16,17

Additionally, certain oils and fats can contain small amounts of vitamin K, and eating these with the vegetables high in vitamin K can increase the vitamin’s bioavailability, since it is a fat soluble vitamin.16 Although the main source of vitamin D is through sun exposure, fatty fish, mushrooms, egg yolks, and fortified foods and beverages.16,17

Saturated fatty acid intake should be limited, as high amounts of SFAs can lead to cartilage degeneration.18 Furthermore, omega-6 fatty acid consumption can increase the risk of inflammation16 and osteoarthritis.18 Safflower and sunflower oils have high levels of omega-6 fatty acids.18 Conversely, omega-3 polyunsaturated fatty acid (e.g., docosahexaenoic acid [DHA], eicosapentaenoic acid [EPA]) intake might protect against cartilage damage and osteoarthritis.16,18

Sources high in omega-3 fatty acids include cod liver oil, mackerel, salmon, sardines, herring, kippers, tuna, and other cold-water fish.16,17

Sources

1. Christiano D. What’s the difference between ligaments and tendons? Healthline. Updated 18 Sep 2018. https:// www.healthline.com/health/ligament-vstendon#function. Accessed 4 Jan 2023.

2. Cleveland Clinic. Tendon. Reviewed 10 Aug 2021. https://my.clevelandclinic.org/ health/body/21738-tendon. Accessed 4 Jan 2023.

3. Cleveland Clinic. Ligament. Reviewed 6 Jul 2021. https://my.clevelandclinic.org/ health/body/21604-ligament. Accessed 4 Jan 2023.

4. Cleveland Clinic. Cartilage. Reviewed 24 May 2022. https://my.clevelandclinic.org/ health/body/23173-cartilage. Accessed 4 Jan 2023.

5. Bordoni B, Varacallo M. Anatomy, tendons. Updated 18 Jul 2022. In: StatPearls [Internet]. StatPearls Publishing; 2022/

6. Hospital for Special Surgery. Tendinitis/ tendinitis. https://www.hss.edu/conditionlist_tendonitis.asp. Accessed 4 Jan 2023.

7. Physiopedia. Ligament. https://www. physio-pedia.com/Ligament. Accessed 4 Jan 2023.

8. Physiopedia. Cartilage. https://www. physio-pedia.com/Cartilage. Accessed 4 Jan 2023.

9. Yale Medicine. Cartilage injury and repair. https://www.yalemedicine.org/ conditions/cartilage-injury-and-repair. Accessed 4 Jan 2023.

10. Noriega-González DC, Drobnic F, Caballero-García A, et al. Effect of vitamin C on tendinopathy recovery: a scoping review. Nutrients. 2022;14(13):2663.

11. Turnagöl HH, Koşar ŞN, Güzel Y, et al. Nutritional considerations for injury prevention and recovery in combat sports. Nutrients. 2022;14(1):53.

12. Tremblay S. Nutrients Needed for Tendons on Ligaments. SFGate. Updated 6 Dec 2018. https://healthyeating.sfgate. com/best-indoor-cycling-bikes-13771759. html. Accessed 9 Jan 2023.

13. Baar K. Stress relaxation and targeted nutrition to treat patellar tendinopathy. Int J Sport Nutr. 2019;29(4):453–457.

14. Praet SFE, Purdam CR, Welvaert M, et al. Oral supplementation of specific collagen peptides combined with calf-strengthening exercises enhances function and reduces pain in Achilles tendinopathy patients. Nutrients 2019;11(1):76.

15. Qiu F, Li J, Legerlotz K. Does additional dietary supplementation improve physiotherapeutic treatment outcome in tendinopathy? A systematic review and meta-analysis. J Clin Med 2022;11(6):1666.

16. Thomas S, Browne H, Mobasheri A, Rayman MP. What is the evidence for a role for diet and nutrition in osteoarthritis? Rheumatology (Oxford) 2018;57(Suppl 4):iv61–iv74.

17. Andwele M. Eat right for your type of arthritis. Arthritis Foundation. 18 Jun 2021. https://www.arthritis.org/healthwellness/healthy-living/nutrition/healthyeating/eat-right-for-your-type-of-arthritis. Accessed 9 Jan 2023.

18. Mustonen A-M, Käkelä R, Joukainen A, et al. Synovial fluid fatty acid profiles are differently altered by inflammatory joint pathologies in the shoulder and knee joints. Biology. 2021;10(5):401. NHR

VARIETY OF HEALTHY EATING PATTERNS LINKED WITH LOWER RISK OF PREMATURE DEATH

Usingdata from 75,230 women and 44,085 men, researchers found that higher scores, indicating greater adherence to the diet, for at least one of four dietary indices (Healthy Eating Index 2015, Alternate Mediterranean Diet, Healthful Plant-based Diet Index, and Alternate Healthy Eating Index), was associated with lower risk of premature death of all causes, as well as cancer, cardiovascular disease, and respiratory disease. Furthermore, higher scores for the Alternative Mediterranean Diet and Alternative Healthy Eating Index were correlated with lower risk of death due to neurodegenerative disease.

Source: Science Daily. Variety of healthy eating patterns linked with lower risk of premature death. 9 Jan 2023. https://www.sciencedaily.com/ releases/2023/01/230109112708.htm. Accessed 18 Jan 2023. NHR

STUDY CHALLENGES “GOOD” CHOLESTEROL’S ROLE IN UNIVERSALLY PREDICTING HEART DISEASE RISK

A National Institutes of Health-supported study found that high-density lipoprotein (HDL) cholesterol, often called the “good cholesterol,” may not be as effective as scientists once believed in uniformly predicting cardiovascular disease risk among adults of different racial and ethnic backgrounds. The research, which was published in the Journal of the American College of Cardiology, found that while low levels of HDL cholesterol predicted an increased risk of heart attacks or related deaths for White adults—a long-accepted association—the same was not true for Black adults. Additionally, higher HDL cholesterol levels were not associated with reduced cardiovascular disease risk for either group. Investigators reviewed data from 23,901 United States adults who participated in the Reasons for Geographic and Racial Differences in Stroke Study (REGARDS). Previous studies that shaped perceptions about “good” cholesterol levels and heart health were conducted in the 1970s, with the majority of participants being White adults. For the current study, researchers were able to look at how cholesterol levels from Black and White middle-aged adults without heart disease who lived throughout the country overlapped with future cardiovascular events. The authors conclude that in addition to supporting ongoing and future research with diverse populations to explore these connections, the findings suggest that cardiovascular disease risk calculators using HDL cholesterol could lead to inaccurate predictions for Black adults.

Source: Zakai NA, Minnier J, Safford MM, et al. Race-dependent association of high-density lipoprotein cholesterol levels with incident coronary artery disease. J Am Coll Cardiol. 2022;80(22):2104–2115. NHR