Your knees carry you through many journeys in life, but as we age or overuse these joints, they begin to show signs of wear and tear. Osteoarthritis, also called degenerative joint disease, is the most common type of arthritis, affecting 80% of those 55 and older.1 This disease is caused by damage or breakdown of joint cartilage between bones over time. Some cases can result in reduced function and disability, limiting affected individuals' ability to perform daily tasks. However, there are things you can do to keep your knees healthy and preserve your mobility throughout your life.
Anatomy of a Healthy Knee
The knee joins the largest bone in the body—the femur—to the tibia. The bottom of the femur, or thigh bone, is connected to the tibia (shin bone) by a cap-shaped piece of bone called the patella, or knee cap. Each of these bones is covered with a thin, smooth coating called articular cartilage.
There are two tough, rubbery pieces of cartilage between the femur and tibia. Combined, these pieces of cartilage are called the meniscus, and act as shock absorbers between the two bones.
The four main ligaments that help control movement and support the joint are the anterior (ACL), posterior (PCL), medial (MCL), and lateral cruciate ligaments. The entire knee is also surrounded by a fluid-filled membrane called a synovial membrane. This membrane produces a fluid that lubricates the cartilage in the joint to reduce friction during movement.2
It can be difficult to maintain this joint when each step you take puts about one-and-a-half times of your body weight worth of pressure on it.3 This is why it's important to take care of your joint early to prevent knee damage.
An active person takes about 10,000 steps each day. This means that each knee is shouldering about 5,000 steps every single day. For an adult weighing 150 pounds, each knee joint bears about 225 pounds per step, or more than 1.1 million pounds per day.
One of the best ways to protect your knees is to avoid injuries. One form of arthritis is post-traumatic osteoarthritis, which develops in the joint that was injured. Physical injury to a joint can damage the cartilage and the bone, changing the mechanics of the joint and making it wear out more quickly.4 The wearing-out process can be accelerated by continued injury and excess body weight.
While you can't avoid all injuries, getting appropriate medical care and making sure the injury heals may help prevent permanent damage.
There are also steps you can take to prevent joint injuries, including:3
- Use the right safety equipment
- Use proper body mechanics when squatting or lifting things
- Stretch before strenuous activity or sports play
- Cushion your joints with supportive shoes, pads for kneeling, or braces
- Use proper form when playing sports or doing activities that require jumping or pivoting
- If you become injured, seek appropriate medical treatment right away
Joint damage isn't something that happens overnight or from one injury. It's a progressive process, with damage building over time.
Maintain a Manageable Body Weight
Being overweight is a major risk factor for problems in the knee. The knee bears a lot of pressure from the body during activities like walking and running. A heavy weight increases the pressure placed on the knee joint—particularly as your level of activity increases. Even small weight losses can help. Maintaining a manageable weight is a good goal to set to protect your joints.3
Regular exercise can also be protective for your joints, but you have to make sure you're doing the right kind of activity—and doing it the right way. Doing the right exercises with the wrong technique can cause short-term injuries and long-term damage to your knee. The following types of exercise can help you stay active while maintaining healthy knees joints.
Low-Impact Aerobic Activity
Since so much pressure is placed on your knees with even a simple step, high-impact exercises refer to physical activities that put a high impact on your joints. High-impact activities like jogging and cross training can be particularly hard on the knees.
On the other hand, low-impact exercises put a low level of impact on joints and are easier on your body. Low-impact activities that can keep you healthy without straining your knees include:
- Elliptical machines
- Tai chi
- Water exercises
Strong muscles make a good foundation for healthy joints. Strength training builds muscles that support joints and helps absorb some of the pressure placed on the knee joint. Strengthening the quadricep muscle in the thigh used to be the go-to, but experts now suggest that overall muscle development is best for knee health.
To provide the best support for your knee, your strength training efforts should focus on:3
- Core strength
- Thigh and upper leg
A physical therapist can help you find targeted exercises, like squats, that can work these muscles without putting too much strain on the knee.
Stretching keeps the muscles and ligaments that support the knee joint flexible and loose, preventing tears that can lead to more damage. Proper stretching can also support the core and hip, and help build strength. Joints become more stiff with age, and experts say increasing your range of motion is key to reducing joint pain. Stretching is also useful during recovery from knee injury or surgeries.