Many patients and some clinicians are concerned that exercise may ‘wear down’ knee cartilage in people with knee osteoarthritis. This concern often arises from the fear that repetitive or high-impact activities overload the knee joint and accelerate cartilage damage.

 

However, exercise – in addition to being a first-line treatment for osteoarthritis – does not seem to harm cartilage and may improve its quality.

 

Systematic reviews consistently show that exercise does not negatively impact knee joint cartilage in individuals at risk of, or with, knee osteoarthritis. Although cartilage healing potential remains contentious, the harms of being sedentary typically outweigh the harms of being physically active. Besides reducing pain and disability, exercise has numerous health benefits, such as reducing blood pressure, and improving cognitive function and mood.

 

Bricca and colleagues (2025) use the analogy of a sponge to explain how cartilage works:

 

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Have you ever played with a sponge?

 

Sponges are fascinating objects that can soak up water and then release it when squeezed. They come in different shapes and sizes, and they’re soft and flexible.

 

Inside our knees, there’s something a lot like a sponge called cartilage, which plays a vital role in keeping our knees healthy. In addition to its sponge-like properties, cartilage in our knees lubricates the knee joint, ensuring smooth movements and acting like a slippery cushion protecting the bones.

 

However, injuries or certain conditions can sometimes cause the cartilage in our knees to become thinner or develop tiny cracks.

 

Although cartilage doesn’t have blood vessels or nerves, it has special cells called chondrocytes. These cells are like tiny repair workers, and they help keep cartilage strong and healthy.

 

As an example, when walking, running or bending your knees, chondrocytes start making important cartilage components like collagen and aggrecan molecules, which help repair and improve cartilage quality. Additionally, such repetitive loading activities (i.e. like a sponge soaking up and releasing water) promote better circulation of synovial fluid within the joint, which delivers essential nutrients to the chondrocytes and helps remove metabolic waste products. This improved nutrient supply enhances the metabolic activity of chondrocytes, supporting their role in cartilage repair and maintenance.

 

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TL;DR: Physical load, if the right amount, is a force for good – instead of ‘wear and tear’, think ‘wear and repair’.

 

As always, consult with a trusted health professional for advice specific to you.

 

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References:

1. Bricca et al. (2025) (PMID: 40536442)