Vitamin C: A Key Factor in Helping Your Knees

Did you know that osteoarthritis affects more than 50% of over 60 year olds?

This disease, indeed, is the most common degenerative joint disorder that affects both small and large joints and it is a leading cause of disability in older adults. The knee is the principal peripheral joint affected resulting in progressive loss of function, pain and stiffness with a negative impact on health-related quality of life.

Because this disease is so prevalent the relevance of this disease, let’s discover together its pathology, risk factors and treatment options to prevent/retard the progress of osteoarthritis and maintain the knee’s function and health.


Impact of Osteoarthritis on Cartilage and Collagen

Osteoarthritis significantly impacts articular cartilage, which gets severely degraded over the course of the disease. The figure below shows a comparison between healthy (left) and osteoarthritic (right) cartilage in the knee.

Articular cartilage is a specialized type of connective tissue found at the end of long bones and within the intervertebral discs. Its unique structure forms a smooth and lubricated surface that allows for a proper joint motion with a low friction coefficient, good shock-absorbing capabilities and minimized pressure on the bone.

Water accounts for 65–80% of the weight of cartilage providing it the possibility of deformation under load, while 10-15% is made up of collagen, which provides tensile strength (defined as the ability to resist a force that tends to pull the system apart).

Notably, type II collagen constitutes 90% to 95% of the total collagen and is specific to articular cartilage. Although it is normally resistant to degradation, specific enzymes called collagenases, are able to degrade it and they have been implicated in the pathogenesis of osteoarthritis.

A measurable increase in type II collagen degradation is seen in an early stage of the disease with a net loss of this type of collagen. This is accompanied by an increase in the synthesis of collagen II to reconstitute the physiological and functional properties of the cartilage. However, the newly synthesized molecules are often damaged, compromising any effective attempts at cartilage repair.

Osteoarthritis is a multifactorial disease that affects the entire joint.  Due to the intimate contact between bone and cartilage, any changes in either tissue will influence the other components (the figure above shows the loss of cartilage and how the bone structure is remodeled).


Risk Factors for Cartilage Loss

There are multiple risk factors for cartilage loss in osteoarthritis. As shown in the image below, the aetiology of this disease is a complex interplay between genetic and environmental factors.

Generalized constitutional factors are related to age, obesity and occupation, adverse mechanical factors include trauma, surgery on the joint structures while some genetic syndromes lead to joint malformations and early-onset osteoarthritis.

By analyzing these risk factors and considering the fact that knee injuries are associated with accelerated osteoarthritis, it is evident that nobody can feel safe!

Thus, let’s discover together the treatment options.


The Therapeutic Challenge of Osteoarthritis

Unfortunately, there are no approved drugs able to stop the disease progression and pharmacological treatments aimed at osteoarthritis are mostly to combat symptoms like pain.  On the other hand, non-pharmacological treatments include exercise, physiotherapy, weight loss, and surgical joint replacements.

On the basis of the fact that once the collagen network is degraded, it cannot be repaired to its original state, the crucial therapeutic challenge is the prevention of these damages.

In this context, the regulation of oxidative stress, which has been described to play an important role in the pathogenesis of osteoarthritis, offers a promising therapeutic approach. Although reactive oxygen species (free radicals responsible for oxidative stress) at moderate levels are essential in many physiological processes of our body, their overproduction in the knee joints is responsible for the destruction of the articular cartilage. Oxidative stress is also strictly correlated with the severity of osteoarthritis of the knee.

Collectively, it has been demonstrated that oxidative stress has a double negative effect:

  1. decreases in the synthesis of collagen II;
  2. promotes the breakdown of molecules of type II collagen.


Do not forget that type II collagen constitutes 90% to 95% of the total collagen of the articular cartilage!

Thus, the maintenance of optimal levels of free radicals is essential for healthy knee joints. Normally, our body gets rid of the excess of free radicals using natural antioxidants such as vitamins C and E, glutathione and various enzymes.

Vitamin C, in particular, is not only a powerful antioxidant but also plays a key role in collagen production. As reported in the image below, limited vitamin C intake is associated with an increased risk of joint injury and pain, cartilage loss and osteoarthritis.

This body of evidence provides for the rationale that a good bioavailability of vitamin C may retard the progress of osteoarthritis.


Vitamin C

Vitamin C (ascorbic acid) is a water-soluble vitamin that was first isolated in 1923 by Nobel laureate Szent-Gyorgyi. The excellent antioxidant effect of vitamin C is due to the fact that it can exist both in reduced (ascorbate) and oxidized forms as dehydroascorbic acid which are easily inter-convertible and biologically active.

Roles and Benefits of Vitamin C

Ascorbic acid is not only an important co-factor for collagen production, the body requires vitamin C also for normal physiological functions essential for our health. It takes part in enzyme activation, oxidative stress reduction and immune system response and contributes to brain health playing a role in Central Nervous System functions.

Vitamin C also helps in the synthesis and metabolism of tyrosine, folic acid and tryptophan and facilitates the conversion of cholesterol into bile acids. Furthermore, some academic articles have shown that it protects against respiratory tract infections and reduces the risk of cardiovascular disease (i. e. hemorrhagic stroke) and certain cancers.

Even though it has so many key roles, our body cannot synthetize ascorbic acid (from glucose) due to the deficiency of the specific enzyme (gluconolactone oxidase). Thus, vitamin C has to be obtained from the diet.

Let the food be the medicine and the medicine be the food

This phrase, stated by Hippocrates around 2500 years ago, seems to be more accurate than ever!

Dietary Sources of Vitamin C

Vitamin C is found in a variety of fruits (i.e. citrus fruits, kiwi, etc.), vegetables (green and red peppers, broccoli, etc.) and juices while animal sources are poor in it (<30–40 mg/100 g).

Vitamin C content, evaluated by the food, is reported in the table below, however, it is important to highlight that the stability of this vitamin is precarious and highly influenced by oxygen, heat, pH, and metallic ions. It is well preserved in frozen foods, indeed, the vitamin C losses during vegetable and fruit storage are up to 70%. Cooking also reduces the vitamin C content of vegetables by 40% to 60%.

When we think of vitamin C, we probably consider oranges and orange juice as good sources, thus it is interesting to learn that orange juice reconstituted from frozen concentrate is a better source of vitamin C as compared with liquid ready-to-drink juice (86 mg per serving vs 39-46 mg per serving).

Fertilization also impacts vitamin C content: the highest concentrations of vitamin C are usually recorded in fruits and vegetables from organic farming.

How Much Vitamin C Does Your body need?

Recommended doses of vitamin C range from 45 mg/day to 155 mg/day. In the table below are reported the reference intake values for children, adolescents, males, females and smokers. Elderly people require higher intakes because of their lower blood concentrations of vitamin C which may be due to chronic diseases or other factors like permanent medication, but not to an effect of aging itself.

Smokers have more metabolic losses and consequently lower plasma levels of vitamin C than non-smokers. Interestingly, when smokers stop smoking, their vitamin C plasma levels increase.

Vitamin C is transported in the plasma as ascorbate. As described earlier, ascorbate is the reduced form of vitamin C. The plasma ascorbate concentration is a good indicator of the vitamin C status. A plasma ascorbate concentration of 50 μmol/l or higher represents an adequate status while levels between 10 and 50 μmol/l indicate an increased risk of deficiency which requires a vitamin C dietary supplement.

Since vitamin C deficiency is a risk factor in the development of knee osteoarthritis, the correction of its concentration is crucial both for primary prevention and as a therapeutic intervention.  In addition, vitamin C supplement has been found to yield multiple potential pain-reduction benefits in knee osteoarthritis.

Valentina Colapicchioni, Ph. D. Valentina Colapicchioni, Ph. D.

I am Scientific Writer and Researcher in Chemical Sciences. I am Italian but I live in Switzerland, the land of chocolate!

I am driven by the passion to not only produce great Science but also render it accessible to a wide audience. For that reason, I created a scientific blog where I address issues of common interest by communicating in an engaging manner that both academic and non-expert audiences can easily understand. Follow me at!

As a researcher I have been working in several academic institutions across Europe:  CNR – National Research Council (Italy), Centre for Life Nano Science (CLNS@Sapienza) at the Italian Institute of Technology- IIT, Centre for BioNano Interactions (CBNI) at the University College Dublin (Ireland) and the University of Rome La Sapienza where I took an active role in several research projects.

Part of my research is focused on preparative nano-chemistry for diverse range of biomedical applications including development of organic (liposomes, polymers, etc). and inorganic nanoplatforms (silica, quantum dots, etc.) for targeted delivery of drugs, genes and vitamins.

My work aimed at better understanding the interactions of liposome-based nanoparticles with biological fluids after their introduction in the bloodstream. I have also developed several liposome formulations with a distinct skill in killing human prostate and breast cancer cells.

My areas of research are Nanomedicine, Liposomes, Nanoparticle Synthesis and Characterisation, Bio-Nano Interactions, Proteomics, Cancer Therapy, Organic Micropollutants, Chemical Sciences.


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