What Causes Osteoarthritis In The Knee? | Two Major Causes And Treatments

Knee wear and tear affects more than 25% of people over 18 years old, making it the most common type of degenerative joint disease. (1) But, what causes osteoarthritis in the knee in the first place?

Well, two things can cause this – plain ol’ aging, or a previous condition that accelerates the cartilage loss. The latter could be a knee injury, a medical condition, and/or the presence of risk factors.

Identifying the cause(s) of knee OA will help you get the right treatment. So, this article will teach you just that – the common causes of this condition and how to treat it.

Here are the topics we’ll cover – tap on any of them to go straight to that section:

• First cause of knee osteoarthritis (aging)
• Second cause of knee osteoarthritis (previous condition)
• 6 Risk factors that make you prone to knee OA
• Treatment for knee osteoarthritis symptoms

1) Natural aging process – A.K.A. “primary OA”

In primary knee osteoarthritis, the healthy cartilage in our knees wears off due to overuse. There’s no clear underlying reason for the wear and tear, other than aging. (2)

See, cartilage is a strong tissue with shock-absorbing properties. It has a lubricated surface – the joint lining – that lets us move our joints smoothly as well.

This tissue can do this because up to 80% of it is made of water, while the remaining 20% is collagen and nutrients. (3) That’s why cartilage can absorb forces so well.

Now, the daily use of our weight-bearing joints inevitably damages them.

This is a completely natural process. When we’re young, our bodies can regenerate the damaged cartilage. It creates a balance between its breakdown and restoration.

But, this balance gets harder to keep as we age. Over time, the cartilage loses water, making it harder for it to absorb the load and protect other structures in your knee joint – like your ligaments or menisci. (3)

As a result, the cartilage gets drier and more fragile, thus wearing off easier.

That, added to the already poor regeneration rate, is one of the reasons why the elderly are more prone to developing osteoarthritis in the knee. (4)

Related: Everything you should know about knee osteoarthritis

2) Injury, medical condition, or risk factors – A.K.A. “secondary knee OA”

In this second type of knee osteoarthritis, the cartilage wears off faster because of a previous condition – an injury, an illness, and/or certain risk factors. It’s not related to aging. (1, 2)

This explains why young patients also suffer from knee osteoarthritis – 16% of people over 15 have this condition. (4)

Now, let’s look at the most common issues that make people prone to develop secondary osteoarthritis of the knee:

Knee injuries

Certain knee injuries can increase the risk of developing knee OA by four to six times. These are (1, 5):

• Meniscus tears
• Ligament sprains
• Knee dislocation (not the same as kneecap dislocation)
• Tibial fracture

If you’ve had any of these injuries, make sure to keep your leg muscles strong. This may reduce the likelihood of having osteoarthritis in your affected joints in the future.

Medical conditions

Some metabolic diseases can make people prone to develop osteoarthritis in their knees.

For these patients, the best doctor for knee pain is a rheumatologist. They are trained to treat joint pain and disability caused by systemic illnesses.

Now, the most common medical conditions that accelerate knee osteoarthritis are:

Rheumatoid arthritis

Like osteoarthritis, rheumatoid arthritis also involves some kind of cartilage damage. But unlike knee OA, it’s caused by an abnormal reaction of the immune system, not overuse.

In this type of knee arthritis, the immune system attacks healthy cells in the joints by mistake. In turn, this causes arthritis symptoms such as swelling, pain, and cartilage degeneration in one or both knees, hands, and/or fingers.

Diabetes

In this chronic disease, there’s an excess of sugars in the bloodstream because the body can’t make insulin, or can’t use it properly. If it goes untreated, diabetes can cause several health issues, including osteoarthritis.

Experts believe this happens because the surplus in blood sugars can cause low-grade inflammation. This accelerates the joint degradation process in return. (6)

Also, the muscles of diabetic patients may not work properly. As a result, their knee joints may not be as stable as they should be, thus increasing the risk of injuries and wear and tear. (6)

6 Risk factors that can make you prone to secondary knee osteoarthritis

Risk factors increase the likelihood of having knee osteoarthritis. The good news is that most of them can be managed. These are:

1) Lack of physical activity

Daily movement and having strong muscles keep the knee joint cartilage hydrated and “squishy.” That way, it can keep its shock-absorbing quality and protect the rest of the joint for longer.

But lack of physical activity makes your muscles weaker. They won’t be able to protect your joint as they should, leaving the cartilage as the only tissue protecting your knees from harm. (7)

This accelerates cartilage breakdown, increasing your risk of having knee osteoarthritis. (7)

Pro tip: You can easily prevent this with a knee strengthening program, preferably guided by a healthcare professional or a certified personal trainer.

2) Participating in certain sports

Playing these sports on an elite level can increase the risk to develop osteoarthritis in the knee joint (8):

• Soccer
• Long-distance running
• Weight lifting
• Wrestling

Yet, researchers aren’t sure if this increased risk is due to the sport itself, the injuries related to these disciplines, or other unknown factors. (8)

Regardless, competitive athletes in these sports should talk with their healthcare team about strategies to minimize the risk of developing osteoarthritis of the knee. (8)

Related: How your doctor diagnoses knee osteoarthritis

3) Your occupation or hobbies

Certain occupations or hobbies can increase the risk to develop knee OA, such as (9):

• Farmworkers.
• Fishers.
• Machine operators and assemblers.
• Craft and trades workers – mechanics, carpenters, builders, plumbers…
• Elementary manual workers – selling goods from door to door, cleaners, garbage collectors…

All these occupations require considerable physical effort for a long period, leading to overuse.

This risk factor is really hard to modify. So, it’s key to manage the other risks in this list to the best of your ability. That way, you can reduce your likelihood of having knee osteoarthritis.

4) Having a BMI >25

Overweight and obese people are four times more likely to develop osteoarthritis of the knee, compared to people with a BMI <25. (7)

It’s unclear why this happens, though. So far, experts believe this has to do with a combination of (7):

• Mechanical factors – the excess load on the joints wears them off faster
• Metabolical factors – the excess adipose tissue promotes low-grade inflammation, which accelerates cartilage degradation
• A previous knee injury

Now, for people with a BMI above 25, even a small amount of weight loss (5-10%) can make a huge difference in their symptoms. It may even delay the progression of knee osteoarthritis. (7, 10)

The main challenge is that it’s hard to lose weight, let alone keep it off. You can increase your chances of success by losing weight slowly and with a combination of dietary and exercise strategies.

5) Genetic predisposition

Sometimes osteoarthritis does run in families – scientists have identified several genes that increase the risk of this condition. (7)

However, having these genes doesn’t mean you’ll develop knee osteoarthritis sooner.

See, genetics aren’t the whole story. Your lifestyle can change the way your genes express in your daily life. This is so important it has a whole field of study, known as “epigenetics.” (7)

In simple terms, this means that you could “turn off” the genes that make you prone to osteoarthritis. You may do this by:

• Keeping a healthy weight
• Consuming as little processed foods as possible
• Getting enough nutrients
• Exercising frequently
• Managing your stress

6) Race and gender

Although more research needs to be done to learn why this happens, current statistics show that (4, 7):

• Women are more likely to develop osteoarthritis of the knee.
• African-Americans are more likely to suffer from severe knee OA symptoms.

Treatment options for knee joint pain and stiffness due to OA

Sadly, there’s no way to restore the already deteriorated cartilage or completely stop the progression of knee osteoarthritis. (1)

The treatments focus on pain relief, managing joint swelling, and keeping the quality of life of the patient. The most common treatments for this knee arthritis include:

Home treatments

These remedies help you relieve pain and joint stiffness. They are key to helping you keep your quality of life as the condition progresses. They include:

• Pain relievers like nonsteroidal anti-inflammatory drugs (NSAIDs) or acetaminophen.
• Heat pads.
• Ice packs.
• Wearing a knee brace.

Check this out: 11 home remedies for knee osteoarthritis that actually work

Conservative treatments

These treatments include physical therapy and injections. Both are effective for osteoarthritis pain management, but they reduce pain in different ways.

Going to physical therapy is the easiest and most efficient way to manage your symptoms. Your physio will design a treatment plan tailored to your specific needs.

Whether they are relieving arthritis pain or getting back to your athletic activity, a therapist will be the best ally in your recovery.

Now, injections help manage pain by using chemicals that reduce symptoms temporarily. They’re a great solution for people that have tried physical therapy for a few months and aren’t responding to the treatment.

This can help: Ranking of 15 treatments for knee OA from best to worse

Surgery

This becomes an option when you’ve tried all the treatments above but your symptoms don’t improve.

Undergoing surgery is a very personal decision. It should be discussed with your doctor and your physio, as results aren’t guaranteed.

There are several surgical options, depending on your age, symptoms, and other factors. They include:

• Knee arthroscopy – for removing bone spurs and doing minor repairs
• Knee osteotomy – for younger patients
• Partial knee replacement
• Total knee replacement

Further reading: When is surgery necessary for knee osteoarthritis? Decision-making guide

FAQs:

Conclusion: Causes of osteoarthritis in the knee

Knee osteoarthritis has two types, according to its cause: primary and secondary.

We know these concepts can look crystal clear on paper, but they aren’t in real life. The truth is that it’s hard to know exactly what causes osteoarthritis of the knee.

However, we hope this article gave you some direction on what could be causing your knee osteoarthritis. That way, you’ll know the best way to treat your pain, swelling, and other symptoms.

Resources

1. Chen, Di et al. “Osteoarthritis: toward a comprehensive understanding of pathological mechanism.” Bone research vol. 5 16044. 17 Jan. 2017, DOI: 10.1038/boneres.2016.44
2. Hsu H, Siwiec RM. Knee Osteoarthritis. [Updated 2021 Jul 25]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK507884/
3. Sophia Fox, Alice J et al. “The basic science of articular cartilage: structure, composition, and function.” Sports health vol. 1,6 (2009): 461-8. DOI: 10.1177/1941738109350438
4. Cui, Aiyong et al. “Global, regional prevalence, incidence and risk factors of knee osteoarthritis in population-based studies.” EClinicalMedicine published by The Lancet vol. 29-30 100587. 26 Nov. 2020, DOI: 10.1016/j.eclinm.2020.100587
5. Snoeker, Barbara et al. “Risk of knee osteoarthritis after different types of knee injuries in young adults: a population-based cohort study.” British journal of sports medicine vol. 54,12 (2020): 725-730. DOI: 10.1136/bjsports-2019-100959
6. Eitner, Annett, and Britt Wildemann. “Diabetes – osteoarthritis and joint pain.” Bone & joint research vol. 10,5 (2021): 307-309. DOI: 10.1302/2046-3758.105.BJR-2021-0119
7. Primorac, Dragan et al. “Knee Osteoarthritis: A Review of Pathogenesis and State-Of-The-Art Non-Operative Therapeutic Considerations.” Genes vol. 11,8 854. 26 Jul. 2020, DOI: 10.3390/genes11080854
8. Driban, Jeffrey B et al. “Is Participation in Certain Sports Associated With Knee Osteoarthritis? A Systematic Review.” Journal of athletic training vol. 52,6 (2017): 497-506. DOI: 10.4085/1062-6050-50.2.08
9. Seok, Hongdeok et al. “The Association between Osteoarthritis and Occupational Clusters in the Korean Population: A Nationwide Study.” PloS one vol. 12,1 e0170229. 18 Jan. 2017, DOI: 10.1371/journal.pone.0170229
10. American Academy of Orthopaedic Surgeons Management of Osteoarthritis of the Knee (Non-Arthroplasty) Evidence-Based Clinical Practice Guideline (3rd Edition). https://www.aaos.org/oak3cpg Published August 31, 2021.
11. Son, Kyeong Min et al. “Absence of pain in subjects with advanced radiographic knee osteoarthritis.” BMC musculoskeletal disorders vol. 21,1 640. 29 Sep. 2020, DOI: 10.1186/s12891-020-03647-x