The knee is one of the largest joints and the primary supporter of the human body's weight. Every day, this joint works non-stop as you walk, climb stairs, stand up from a sitting position, and exercise. Because of its significant role, the knee experiences significant mechanical stress every time we move.
Among the various risk factors for knee joint disorders, such as age, injury history, leg shape, and genetics, weight is one of the most modifiable. Maintaining a healthy weight is not only important for overall health but also one of the most effective ways to maintain long-term knee health.
So why does weight have such a big impact on knee health?
The Effect of Body Weight on Knee Health
1. Every kilogram of body weight places multiple loads on the knees
Many people think that their knees simply support the weight of their body, as seen on the scale. In fact, based on biomechanical principles, the pressure on their knees is far greater than their own body weight.
- Walking on a flat surface: about 2–3 times body weight.
- Climbing stairs: about 3–4 times body weight.
- Going down stairs: about 4–5 times body weight.
- Squatting or kneeling: can reach 5–7 times body weight.
This means that every 1 kilogram of weight gain increases the load on the knees by approximately 2–4 kilograms per step. Therefore, just 5 kilograms of excess weight can increase the load on the knees by approximately 10–20 kilograms per step. Imagine how many thousands of steps a person takes each day. This additional load will continue to be applied to the knee joints for years, accelerating the wear and tear process.
2. Excess Body Weight Accelerates the Occurrence of Osteoarthritis
Between the ends of the bones in the knee joint is a protective layer called cartilage. This surface acts as a cushion, allowing the knee to move smoothly without excessive friction.
Continuous mechanical stress from excess weight causes cartilage to deteriorate, lose elasticity, and eventually thin. This condition is known as osteoarthritis, often referred to as "arthritis."
However, osteoarthritis is not simply a matter of calcification. This disease is a degenerative process that involves all components of the joint (whole joint disease), including the cartilage, the underlying bone (subchondral bone), the menisci, the synovial lining, the ligaments, and the surrounding tissue.
As a result, sufferers may experience:
- Pain during activity
- Knees feel stiff especially after waking up or sitting for a long time
- Swelling
- 'Creak-creak' sound when moved
- Decreased ability to walk or carry out daily activities
3. Body Fat Not Only Adds Weight, But Also Triggers Inflammation
Many people think fat only serves as an energy reserve. However, adipose tissue is a metabolically active organ.
This tissue produces various substances called adipokines and inflammatory mediators, such as leptin, TNF-α, and interleukin-6 (IL-6). These substances can increase low-grade chronic inflammation in the body.
This inflammation also accelerates the breakdown of cartilage and joint tissue. Therefore, in obese individuals, knee damage occurs not only due to greater mechanical stress but also due to biological processes that accelerate joint degeneration.
4. Excess Weight Changes the Way Your Knees Work
Excess weight, especially that concentrated in the abdominal area, can shift the body's center of gravity. As a result, the body will adjust the way it stands and walks to maintain balance.
These changes can increase stress on certain parts of the knee and exacerbate pre-existing leg axis abnormalities, resulting in uneven load distribution. Over the long term, this condition can accelerate wear and tear on one side of the knee joint and increase the risk of developing osteoarthritis.
The Good News: Even a Small Amount of Weight Loss Can Make a Big Difference
Research shows that weight loss of around 5% of initial body weight can provide significant improvements in knee pain and function in people with osteoarthritis.
Various international guidelines also recommend a minimum weight loss of 5%, and greater benefits can be achieved if the loss reaches 10% or more, especially when combined with exercise and muscle strengthening exercises.
In other words, you don't have to reach your ideal weight immediately to start feeling the benefits. Even gradual weight loss can have a positive impact on knee health.
What Can Be Done to Maintain Knee Health?
1. Manage Your Weight
Consume a balanced nutritious diet with the appropriate number of calories to ensure your weight remains within the ideal range.
2. Choose Low Impact Sports
Activities such as swimming, cycling, walking, or using an elliptical machine provide fitness benefits without putting excessive stress on the knees.
3. Strengthen the muscles around the knees
The quadriceps, hamstrings, gluteal muscles, and core muscles play an important role in supporting and stabilizing the knee so that the load on the joint can be reduced.
4. Stay Active and Move
If knee pain begins to appear, avoid activities that aggravate the symptoms. However, don't stop physical activity completely, as lack of movement can actually lead to muscle weakness and joint stiffness.
Consult a specialist immediately
Body weight and knee health are closely related. The heavier a person is, the greater the mechanical load and inflammatory processes the knee joints must endure.
Maintaining an ideal body weight is one of the most effective steps to prevent or slow the progression of osteoarthritis, reduce knee pain, and maintain quality of life into old age.
If you begin to experience persistent knee pain, stiffness when moving, or difficulty performing daily activities, don't wait until the symptoms worsen. Consult a doctor to determine the cause and receive appropriate treatment as soon as possible.
Article written by Dr. Akbar Rizki Beni Asdi, Sp.OT, Subsp.PL(K), FICS, AIFO-K (Orthopedic & Traumatology Specialist, Hip & Knee Consultant at EMC Pulomas Hospital).