Knee Pain Going Down Stairs?

• Do you experience knee pain walking down stairs?
• Ever had knee pain going down stairs but not up stairs?
• Do you want to know what you can do to reduce your knee pain when walking down stairs? 

After reading this article you will have a better understanding of why going down stairs is often more painful than going upstairs.

Many of my patients are confused by this. Surely going up stairs puts more pressure through your knees?

The post will touch on the physics of why this is not the case and why going down stairs places more load through your knees.

Read to the End

Please do not get put off by the long words and the complex sounding physics, all will become clear if you read to the end.

This article will help you understand how to create or adapt an exercise program to manage your knee pain.

Moment Arms

I will now go into the physics around the forces placed on the knee whilst going up or down stairs.

External Knee Flexion Moment

One of the things we need to consider is something referred to as the external knee flexion moment. This sounds like a complicated term, but I’ll try to simplify this for you now.

An external force, the weight of your body, is pushing in a downwards direction. The opposite of this is the ground reaction force, which pushes the foot in an upwards direction. These forces act around the knee joint resulting in it bending (knee flexion). 

Working out the Moment Arm

First, we need to look at the direction of the body weight and the ground reaction force acting through the foot. 

In this example I am performing a shallow squat.  The weight of my body is being pulled by gravity in a downwards direction (blue arrow).  The ground reaction force is acting in the opposite direction and is pointing upwards (red arrow).

Moment Arm Length

To work out the moment arm we need to draw a line from the centre of the knee joint back to where it meets the ground reaction line (red line). This line should be perpendicular to that of the ground reaction line. 

This new green line, shown below, is the external knee flexion moment (EKFM) arm.

Internal Knee Extension Moment

Without an opposite force to the external knee flexion moment our knees would continue to bend underneath us until we ended up in a heap on the floor.

This opposite force comes in the form of the contraction of the quadriceps muscles in the front of your thigh. Your quadriceps contract to create the internal knee extension moment.  

Any force created by the quadriceps muscles results in pressure through the front of your knees and through the patella tendon (the tendon just underneath your knees). 

The amount of force that is created by the quadriceps will determine how much pressure is placed through your knees. The length of the external knee flexion moment arm influences the force required from the quadriceps muscle. 

A longer moment arm will place more force through the knee than a shorter moment arm. Imagine a lever in the form of a wrench. A longer lever has the ability to create a larger force with less input.

Moment Arms on the Stairs

Let’s take a look at what this looks like going both up and down stairs. This should then answer your question of why you get more knee pain when going down stairs.

Moment Arm Going Up Stairs

In the example below, I am stepping up on to the step.  As I step up, my bodyweight will act in a downwards direction through my front foot.  The ground reaction force works in the opposite direction as shown by the red arrow below.

The moment arm is once again determined by the perpendicular green arrow pointing from the centre of the knee back to the ground reaction force line.  Given my knee is almost directly over my foot, the moment arm of the external knee flexion moment is very short.

Compare this moment arm length to the previous example where I am squatting.  The moment arm is a lot less, meaning that the force needed by the quadriceps is also less (the muscles around the hips are doing more of the work in this case).  A smaller force produced by the quadriceps muscle results in less force being placed through the front of the knee.

Moment Arm Going Down Stairs

Now let’s take a look at the moment arm length when going down stairs. In this instance I am stepping down from the step to the floor.

As I start to step down my bodyweight presses down through the front of my back foot.  Once again, the ground reaction force works upward from the point of contact (red arrow).

We work out the external knee flexion moment arm length out in the same way as the two previous examples. The green arrow points from the centre of the knee back to where it meets the ground reaction force line.

Straight away you should be able to see that the moment arm in green is much longer than in the previous two examples. Remember a longer moment arm is like a longer lever, it places more force through the knee.

Why Do You Experience Knee Pain Going Down Stairs?

The various structures around your knees have developed the ability to tolerate a particular amount of force that is placed through them.

If you place a force through your knee that is less than or equal to the force that you can currently tolerate you will likely be pain free.

If you place a force through your knee that exceeds what you can tolerate then it can result in those structures around your knee becoming sensitive and angry.  When a structure is sensitive it is often experienced as pain.

We have already established that there is a longer moment arm when going down stairs compared to up.  As a result, going down stairs will place more force through your knee. Given that a larger force is more likely to cross the threshold amount required to cause sensitivity, you can now see why you are more likely to experience knee pain going down stairs.

What Can I Do About Knee Pain Going Down Stairs?

Reduce the Forces Temporarily

A high force or load through your knee isn’t necessarily a bad thing.  However, if the higher loads reproduce your pain, it just means that you have placed more load through it than you can tolerate.

Initially you will need to reduce the load that you place through your knee enough that the knee begins to settle.  You don’t need to rest completely; the force just needs to be reduced enough so that it doesn’t cross the threshold amount to cause pain.

Gradually Increase the Load

In order to tolerate a higher load again, you will need to expose your knee to gradually increasing loads over time.  This will allow the structures around your knee to adapt positively so that they can learn to tolerate those higher loads and forces again.

The following approaches can be used to achieve this:

Smaller Moment Arm

The best way to build this tolerance in your knee is to strengthen your muscles in a position with a shorter moment arm. In this position you can start to load the muscles with heavier weights.

An example of this would be a box squat.  Place a raised surface behind you that allows you to perform a shallow squat but stops you from going so deep that you provoke your pain.  A shallower squat has a smaller moment arm than a deeper squat, so is likely to be tolerated.

If the box squat is comfortable with your bodyweight then you can start to add a weight that you are able to tolerate.  In order to progress further, the weight that you use can gradually be increased. Alternatively you can slowly reduce the height of the surface.

Longer Moment Arm with Less Resistance

Alternatively, you can choose an exercise with a larger moment arm but reducing the resistance that you use.

An example of an exercise with a longer moment arm is a knee extension (using a knee extension machine or a resistance band).  The seated position means that your bodyweight is not being placed through your knee.  You can set the machine so that you are moving a weight that is less than your bodyweight, one that you are able to tolerate.

Once you find a starting weight, you can gradually increase the weight used so that the knee adapts and learns to tolerate a higher load.

To learn more about regressing exercises in order to find a starting point, read 7 Functional Movements: Progressions, Regressions and Modifying Around Pain.

Robust and Resilient

Both approaches discussed above have the same aim of allowing you knee to adapt to tolerate higher loads.  Your overall aim is to perform exercises that have a longer moment arm combined with a high external resistance.    

I would even suggest creating a program that includes both approaches in the same workout.  For more ideas of an exercise program that you could start with, read Exercises for Knee Pain.

If you can tolerate an exercise with a longer moment arm in the gym with more weight, you will be able to deal with any bodyweight movement that happens in your day to day life.

You will create a strong, robust and resilient body! 

Recommended Reading:

The False Dichotomy of Open vs Closed Kinetic Chain – The Science PT

Much of this post was inspired by the work of Erik Meira aka The Science PT. For any physiotherapists or other related therapists that have found themselves reading this post, I highly recommend that you start listening to his podcast – The PT Inquest Podcast.  He also has some great CPD courses, one of which I’ve been lucky enough to attend.

Recommended Equipment/Books

Go to the Recommended Products page for a full list all the products and books that I recommend.

This post was written by myself, Chris Tiley, a physiotherapist based out of Movement Therapy Clinics in Harborne, Birmingham. For more information on how I can help you visit christileyphysiotherapy.com