Are you dealing with achy knees due to osteoarthritis? Knee osteoarthritis (OA) is a common condition affecting millions of people worldwide, causing pain, stiffness, and reduced mobility. Simply put, knee osteoarthritis can limit your activities and reduce your quality of life. While we know exercise can impact knee health, the relationship between specific types of exercise, muscle mass, and the risk of developing knee osteoarthritis is less clear. However, a recent study published in the esteemed journal Journal of the American Medical Association (JAMA) sheds new light on this important topic.
Key Findings: Low Muscle Mass and Weight-Bearing Exercise
The study published in JAMA focused on 5,000 individuals and followed them for 6.33 years. Some of the participants were physically active and did weight-bearing activities regularly while some were sedentary. They found that subjects with less low-limb muscle mass, in other words, “skinny legs,” were at higher risk of developing knee osteoarthritis. The higher risk was also significant, a greater than 50% risk per unit of metabolic impact or about 1.53 per unit increase for the subgroup with the lowest third of lower-limb muscle mass.
In contrast, study subjects who had higher amounts of lower-limb muscle (in the middle and upper tertiles) did not have a higher risk of developing osteoarthritis when they took part in weight-bearing exercise.
What are the takeaways? If you’re a runner or do weight-bearing exercises of any type, make sure your lower body is strong and contains enough muscle. It also shows that keeping your legs strong and boosting the muscle mass in your lower body may help protect against osteoarthritis of the knee. This goes along with other studies that show strengthening the lower body muscles, particularly the quadriceps, may protect against knee osteoarthritis.
Developing lower knee osteoarthritis is less of a worry if you do low-impact exercise, like swimming or cycling. The study found people who did low-impact exercise weren’t at higher risk even if they had less muscle in their lower extremities. But also know that if you don’t do high-impact exercise, you’re not getting the bone-health benefits that this type of exercise offers.
Implications for Knee Health
These findings suggest that if you have low muscle mass in your lower body, you should be cautious about doing lots of running, playing sports that require running or jumping or even gardening, as a lack of lower extremity muscle mass may put your knees at risk.
But there is something you can do to mitigate the risk, start a strength-training program, and build more muscle and strength in your lower body. Strong quadriceps support your knees and help them stay healthy as you go through the activities of life. But until you have enough muscle mass, it’s best to limit high-impact weight-bearing exercise, beyond walking, especially if you’re at high risk for knee osteoarthritis.
Most importantly, don’t let it discourage you from staying active. Start working on building lower body strength. Squats and lunges are a good place to start and gradually increase the resistance by holding weights as the movements become easier. The muscles to strengthen for better knee support are your quads, hamstrings, glutes, and calves. And balance it out by doing upper body training too.
If you’re just starting, begin slowly by focusing on form. Don’t add weight initially. Give your bones and soft tissues a chance to adapt to the new stress you’re placing on them.
The Bottom Line
Now you have another reason to strength train and boost muscle mass in your lower body – it’s beneficial for the health of your knees. The extra support that strong quads, hamstrings, glutes, and calves provide are like a support system for your knees.
Also, be aware of other risk factors for knee osteoarthritis. These include:
- Older age – Osteoarthritis risk goes up with age, especially after the age of 50
- Obesity and overweight – Being overweight or obese puts more stress on the knee joints, increasing their susceptibility to degeneration.
- Female gender – Women are at higher risk of developing knee osteoarthritis than men.
- Previous knee injury or trauma – Injuries to the knee joint, even if it occurred many years ago, can boost your risk of knee degeneration and osteoarthritis.
- Repetitive stress on the knees – Playing sports or being employed in occupations that force you to squat, kneel, or lift heavy items increases the risk, especially if you lift or squat improperly.
- Genetics – Some people may inherit a genetic predisposition or tendency to develop osteoarthritis. Take a close look at who has it in your family.
- Bone deformities – Being born with malformed joints or defective cartilage places you at higher risk.
- Certain metabolic diseases – If you have diabetes and or a condition called hemochromatosis (excess iron storage), your risk of osteoarthritis rises.
- Joint laxity or instability – Looser, more unstable knee joints are a risk factor, especially in women.
If you have any of these risk factors, taking care of your knees is even more important. Take it to task by committing time to strengthen your lower body, especially your quads, as strong quads are your best defense against osteoarthritis and knee injury.
References:
- Gever J. Study: Skinny-Leg Runners Face Higher Rates of Knee Arthritis. Medpagetoday.com. Published April 30, 2024. Accessed April 30, 2024. https://www.medpagetoday.com/rheumatology/arthritis/109892.
- Exercise for bone health. Theros.org.uk. Published 2024. Accessed April 30, 2024. https://theros.org.uk/information-and-support/bone-health/exercise-for-bones/
- Law TD, Clark LA, Clark BC. Resistance Exercise to Prevent and Manage Sarcopenia and Dynapenia. Annu Rev Gerontol Geriatr. 2016;36(1):205-228. doi: 10.1891/0198-8794.36.205. PMID: 27134329; PMCID: PMC4849483.
- Primorac D, Molnar V, Rod E, Jeleč Ž, Čukelj F, Matišić V, Vrdoljak T, Hudetz D, Hajsok H, Borić I. Knee Osteoarthritis: A Review of Pathogenesis and State-Of-The-Art Non-Operative Therapeutic Considerations. Genes (Basel). 2020 Jul 26;11(8):854. doi: 10.3390/genes11080854. PMID: 32722615; PMCID: PMC7464436.
- Fernández-Moreno M, Rego I, Carreira-Garcia V, Blanco FJ. Genetics in osteoarthritis. Curr Genomics. 2008 Dec;9(8):542-7. doi: 10.2174/138920208786847953. PMID: 19516961; PMCID: PMC2694558.
- “Osteoarthritis: MedlinePlus Genetics.” https://medlineplus.gov/genetics/condition/osteoarthritis/.
- “Arthritis of the Knee – OrthoInfo – AAOS.” https://orthoinfo.aaos.org/en/diseases–conditions/arthritis-of-the-knee.
- “Knee Arthritis | Johns Hopkins Medicine.” https://www.hopkinsmedicine.org/health/conditions-and-diseases/knee-arthritis.
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