So the simple answer is yes, your weight will affect the health of your joints.
There are two ways that being overweight can lead to joint issues, being increased mechanical stress commonly seen in Osteoarthritis, and inflammatory markers we often see in cases like Rheumatoid arthritis. In fact reducing systemic inflammation is a keystone to healthy joints, which we will cover in more detail in our 5th blog.
So how does being overweight contribute to wear and tear of the joints?
Well , like all things in the body, the mechanisms are complex, and there is still a ton of research being done on the best ways to avoid joint wear and tear, but the general model for mechanical joints issues relates to
- Increase forces going through the joints
- Shifts in center of gravity
- Uneven loading through joints
- Decrease in physical activity as weight increases
So lets take a look at each of these
Increase forces going through the joints
When walking for example, the force on your knees is equivalent to around one and a half times your body weight. So if a 90 kg person is going for a walk, there’s about 136kg of forces going through the knees, and that’s just on a flat, even surface at a comfortable pace.
Now add in an incline and the forces start to really ramp up, going up and down a flight of stairs can easily be two – three times bodyweight of force going through the knees. So if our 90 kg walker started to go up a flight of stairs we are looking, his knees will start o fell loads of 180 – 270 kg. If you squat down to tie your shoes or pick up an object off the floor then the forces are even greater up to five to six times body weight
These are considered to be fairly normal tasks, walking, climbing a set of stairs, and tying your shoes, however the more excess body weight you have the harder it gets to do, and the more forces are placed on the joints.
Now if exercise is structured and graded correctly to suit the individual’s unique body demands then exercise for folks who are overweight is highly recommended. However too much, or not enough of the right type of exercise can lead to excessive joint wear and tear, setting up common issues such as degenerative arthritis, meniscus tears, and joint pain.
Shift of center of gravity
Your center of gravity is the point where the mass of your body distributes evenly in the body, and for us bipedal humans, it usually sits just below the belly button. The center of gravity shifts as the body changes shape in space, for example if you squat down, your center of gravity lowers, if you lean out to one side, your center of gravity shift slightly tot he side you lean toward.
Now as folks increase in body weight, or lets call it what it is, they get fatter )increase adipose tissue storage) they tend to store the extra kilograms in region of the body. For men it tends to be more on the belly, for women hips and thighs. We don’t really have any control on where the body stores extra fat, it distributes evenly across the body to maintain balance. The issue becomes for those folks who are really starting to increase body weight, that the center of gravity starts to shift, generally anteriorly as the majority of stored fat goes on the belly hips and thighs. This extra loading creates an anterior rotation of the pelvis, which in turn changes the angles of the knee, hips and lower back joints, leading to a change in the load distribution through the joints
Uneven loading through joints
In essence the loading starts to become uneven through the skeletal system, and with the uneven loading we see structural changes occur in the muscles, bones, joints and ligaments. For example as the hips tilt more anteriorly it tends to create a medial bend in the knee joint, which then loads up the meniscus unevenly. This uneven loading can produce changes in the cartlidge, which in a balanced system will favourably respond by growing more collagen fibres, and generally becoming a tougher tissue abel to handle the increasing loads. However, as we saw from above, increase weigh can really ramp up the forces, and with the increase forces distributed unevenly we start to set up a gradual wear and tear process.
Decrease in physical activity as weight increases
So as folks increase in body weight, and joint pain starts to become an issue exercise becomes increasing difficult. At first the stairs were just hard to get up, a little knee stiffness, and aching, with some huffy puffiness at the top as you catch your breath. Then you start to skip the stairs and take the elevator, because well its just a bit easier. Next week you try the stairs again and find it harder than before, so you just stop taking the stairs altogether and the elevator is your passive mode of transport up to the office.
You have effectively stopped doing one of the most important things you can do to prevent or help with your knee pain, exercise.
The right type of exercise is absolutely critical for joint health and longevity. Sure your can get away with poor form squats and deadlifts for a little while, but sooner or later those bad reps add up. We know for example that a disc herniation is rarely a traumatic, good to bad injury, but rather a gradual build up of wearing down the discs structural integrity, in some studies they suggest about 20,000+ repetitions before the discs start to wear…so those 100 situps a day seem like a good idea, but they could potentially be doing you long term harm, particularly if your program is not designed to promote systemic muscular balance, reduce loading forces, and address uneven joint distribution.
We also know that joints love the right amount of loading, they respond very well to the correct amount of load, it promotes growth and healing of the joints and is a critical aspect of healthy joints. Additionally exercise is pretty darn handy if you want to lose weight, the benefits of relating metabolism with good diet, and an intelligent approach to exercise can literally save you years of pain and discomfort, and will save you a ton of money by avoiding surgeries, time of work, and countless visits to doctors, specialists and symptomatic treatments.
Ig you are overweight, and have joint pain and not sure where to start that’s ok, its can be pretty scary, and a little confusing on what’s the best thing to do. Thats where Exercise Physiology can help, as a specialist in exercise I can guide you through the step by step process of restoring your joints to optimal health, so you can go for a walk, take that flight of stairs, and do your shoes up without the fear of paying for it later.