Updated: Jul 26, 2018
Knee Caps ...What are they good for ?
Ever wondered why you have kneecaps ? Maybe not. I’m sure you have more interesting things to ponder; however they are pretty cool. Below is a video of how the knee cap allow us to move our legs with less effort. I like less effort, how about you?
So let me introduce you to the patella or as its more commonly known the knee cap; the bony lump that is found at the front of your knee. It’s a sesamoid bone which means it is formed and contained within the tendon attaching the quads to the tibia (lower leg bone).
So what does it do ?
Well it helps reduce the amount of effort we need to straighten the knee by about 33-50%. It does this by increasing the lever arm of the muscle tendon unit (that all went a bit physics didn’t it?). So it helps us be much more efficient in the movement of our leg and reduces the amount of energy we need to do the things we take for granted such as squatting, going up or down stairs, etc.
So why do I want to talk about knee caps ?
Well it is probably the most common knee pain that we see in the clinic and can be a source of pain for a wide range of age groups; from adolescents to the oldest of children - those in their 70’s and beyond. This is probably one of the reasons it has so many names but really comes down to pain behind the patella.
It is often caused by irritation to the cartilage at the back of the patella as well as the surrounding soft tissues.
The under surface of the patella is a V shape and has some of the thickest cartilage in the body and this allows smooth movement on the femur which has a U-shaped cartilage covered groove when we bend and straighten the knee. It also helps the knee tolerate the forces that are put through the joint when we squat to sit, go up and down stairs, walk or run. This animation below gives you a good idea of the structure and function of the patella.
When your knee is straight there is no contact between the patella and the femur and that is why you can move it from left to right quite easily with your fingers, especially when the thigh muscles are relaxed. As you bend the knee the patella starts to slide into the femoral groove at about 20 degrees and stays in the groove until 70-80 degrees flexion. So the maximum contact between the patella and the femur occurs when we go up and down stairs or squatting.
Pain will occur when there is injury to the cartilage on the patella when we bend the knee.
If we can identify where in the range of movement the pain occurs (where in your bend the pain begins) then we can have a good guess where the problem on the patella is. This then gives us good info in where the best ranges of motion to train the knee are.
In our next blog I will have a chat about about the different causes of patellofemoral pain and our top tips to get rid of this condition. In English that means I'll have a chat about pain behind the knee cap.