Those achy knees! Many people have them. The most common cause of knees that are stiff and painful over the age of 50 is osteoarthritis of the knee. Osteoarthritis affects 7 out of 10 people over 50 and the risk climbs with age. Knee osteoarthritis is the most common form of arthritis, although there are over 100 different forms of arthritis. Knee osteoarthritis becomes more of a concern as people age due to age-related joint deterioration.
Why is knee arthritis so common? Since humans are weight-bearing, the weight of their body places added force on their knees, and the force is proportional to body weight. That’s why people who are overweight or obese have a higher risk of developing osteoarthritis of the knee. Unlike rheumatoid arthritis, which has an inflammatory component, osteoarthritis is a degenerative form of arthritis related to wear and tear.
Arthritis of the knee can be asymptomatic in the early stages and only appear on an x-ray. In those with symptoms, the pain and discomfort vary in severity from mild to severe osteoarthritis that requires joint replacement.
Osteoarthritis of the knee can cause pain, stiffness, and difficulty performing daily activities. The discomfort of osteoarthritis is often triggered by movements like walking up and down stairs, getting up from a chair, or heavy lifting.
Knee Injury as a Risk Factor for Osteoarthritis
Beyond obesity, another risk factor for developing arthritis in the knee is a history of a knee injury. Some of the most common knee injuries are a tear of a cruciate ligament or a torn meniscus in the knee.
Of the two types of a knee injury, a torn cruciate ligament is the most serious. The cruciate ligaments are two strong bands of fibers located inside the knee area. These fiber bundles connect the thigh bone, called the femur, to the shinbone, called the tibia.
Every person has two cruciate ligaments in each knee. These ligaments play an important role in knee stability. When they tear, especially when torn completely in half, serious complications can occur. For an athlete, a torn cruciate ligament can be a career ending event. Without treatment, it can lead to chronic instability and damage to the cartilage that causes degenerative changes that lead to osteoarthritis.
A meniscal tear is a common sports injury that occurs when the cartilage of the knee joint tears. The cartilage acts as a cushion between the bones of the knee, and a tear of this cartilage can be a painful and disabling injury. A meniscal tear can occur from an accident or from playing contact sports, like football or basketball. In some cases, there is no history of trauma, and the meniscal tear occurs spontaneously.
Both types of knee injuries are more common in athletes, especially those that play contact sports or take part in sports that require changing directions quickly. Other knee injuries that are more common in athletes and active people are fractures of the patella (the knee bone) or a dislocation of the patella.
Osteoarthritis of the Knee: How Much Does a Knee Injury Increase the Risk?
A study published in the British Journal of Sports Medicine followed people who experienced knee injury at a young age. The follow-up period was 19 years. During that time, 11.3% of the subjects who sustained a knee injury developed osteoarthritis of the knee, while only 4% of those who didn’t injure their knees developed it.
Tears of cruciate ligaments and torn menisci both were linked with higher rates of osteoarthritis of the knee. In all, having a knee injury of any type raised the risk of developing osteoarthritis of the knee by 6-fold. Tears of cruciate ligaments, torn menisci, and fractures of the knee carried the highest risk in the study. So, both torn cartilage and menisci are strong risk factors for osteoarthritis of the knee.
What Can You Do to Lower Your Risk of Knee Arthritis?
You can’t undo a history of injury, but there are two ways to lower your risk of developing knee osteoarthritis, whether you’ve had a knee injury or not. One is to maintain a healthy body weight. The pressure on your knees is proportional to how much force you place on them, and that depends on your body weight. Losing even a modest amount of body weight can reduce the force on your knees.
The other is to strengthen the muscles that stabilize your knee joint – your quadriceps muscles. Strong quadriceps protect the knee against injury and absorb the force your knee joint would otherwise be subject to when you walk, run, or jump. Squats and lunges are excellent exercises for doing this, but approach lunges with caution if you already have knee problems. If you do them, make sure your knee doesn’t extend over your ankle when you lunge.
There’s little evidence that high-impact exercise in moderation increases the risk of knee arthritis in the absence of knee injury, but you should avoid high-impact exercises, like jumping or running, if you already have knee arthritis. Your knees don’t need the extra force that landing from a jump inflicts on your joints.
The Bottom Line
Take care of your knees; you need them to last a lifetime. Avoid injury as much as possible, and strength train to build stronger quadriceps but use good form. Don’t overdo the high-impact exercise, especially if you have a history of knee injury or already have osteoarthritis. Keep moving though!
References:
Snoeker B, Turkiewicz A, Magnusson K, et alRisk of knee osteoarthritis after different types of knee injuries in young adults: a population-based cohort studyBritish Journal of Sports Medicine 2020;54:725-730.
“Osteoarthritis of the Knee – Arthritis Foundation.” arthritis.org/diseases/more-about/osteoarthritis-of-the-knee.
Driban JB, Eaton CB, Lo GH, Ward RJ, Lu B, McAlindon TE. Association of knee injuries with accelerated knee osteoarthritis progression: data from the Osteoarthritis Initiative. Arthritis Care Res (Hoboken). 2014 Nov;66(11):1673-9. doi: 10.1002/acr.22359. PMID: 24782446; PMCID: PMC4211979.
“Knee Arthritis – Mayo Clinic Orthopedics & Sports Medicine.” sportsmedicine.mayoclinic.org/condition/kneearthritis/.
“Arthritis of the Knee – OrthoInfo – AAOS.” orthoinfo.aaos.org/en/diseases–conditions/arthritis-of-the-knee.
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