Yesterday, we kicked off knee week by talking about some of the common mechanics behind overuse injuries in the knee. In today’s post, we are going to get more specific and start grouping injuries together based on the common mechanical limitations they share. More specifically, today we are going to talk about injuries that arise from mobility restrictions behind the knee.
Jumpers vs Runners Knee
Jumpers and runners knee are the common names for injuries affecting the knee cap. In the case of jumpers knee we are talking about patellar tendonitis where the tendon itself is irritated/inflamed. In the case of runners knee we are talking about patellofemoral syndrome or PFS. In this case, the cartilage under the knee cap is damaged/irritated due to increased strain on how the patellofemoral joint tracks as you bend and straighten your knee. What do both share in common? They start due to a mobility restriction/muscle imbalance in the knee joint itself. These restrictions then shift an increasing workload onto the smaller patellofemoral joint which breaks down over time.
What does that mean?
When we look at anatomy pictures of the knee, it’s easy to to make the assumption that there is one “knee joint”. While this is technically true, it is misleading. There are two components that make up the knee joint. The first and larger component is the tibiofemoral joint which is where the femur (thigh) and tibia (shin) meet. In this joint, movement is achieved by the femoral condyles rolling and sliding atop the tibial plateau. There is also a little bit of rotation allowed at this joint to lock it out straight and then to unlock it as the knee bends again. The second, smaller component, is the patellofemoral joint where the patella moves over these bones to assist with mechanical advantage as a large sesamoid bone. Here is a visual to show you the two joint lines.
Why is that important?
While it’s easy to overlook the tibiofemoral joint and focus on the knee cap where your symptoms are, it is most likely the culprit in both of these injuries. The rolling and sliding of the femur over the tibia (shin bone) is what puts the knee in good position so that the knee cap can track properly to produce the power required for running and jumping. If that joint isn’t moving properly (the femur is unable to move on the tibia), it can increase the strain on the quads and the patellar tendon. This gives you two things to fix: 1) the mechanics behind it, and 2) the symptoms that are a result of those mechanics.
To fix those mechanical problems, we need to look behind the knee. Typically in overuse injuries, mobility restrictions are the trigger that starts it all. This could be from insufficient recovery where muscles stiffen up from training/racing. Over time, those restrictions become more permanent and muscle imbalances develop. In the case of patellar injuries, the hamstrings get stuck in that tight position and become weak. This causes the quads to become the dominant muscle group in terms of workload.
So what causes problems behind the knee?
Let’s go back to the picture above for a moment. The hamstrings get top billing as the problem, but as you can see, the gastroc is also a key player. Both the gastroc and hamstrings actually criss cross behind the knee. This means that both are probably what’s keeping you from full straightening your knee. When one is tight, the other is usually tight as well.
The easiest way to look for this restriction is to test it by sitting on the floor with your knee out straight in front of you. Press the back of your knee flat into the floor and pick your heel up. You should not be able to slide your hand under your knee. You should, however, be able to lift that heel up. The main difference in the pictures below is how well the gastroc moves. On the left, the hamstring is stretched at both the hip and knee. On the right, the gastroc is stretched at both the knee and ankle. We want to get to the one on the right!
So how do I fix it?
The important thing to realize with these injuries is that we need to do two things:
- We need to fix the restrictions/imbalances that are limiting the tibiofemoral joint and overloading the patellofemoral joint. Are the mobility restrictions limited to the muscles? Or are the joints on either side of the knee also contributing? Are the muscles on both sides of the knee strong enough to support the activities or has the imbalance started to work against this?
- While fixing the underlying mechanical issues to address the cause, we also need to heal the injury itself. In the case of patellar tendonitis, we need to cure the inflammation along the tendon. In the case of PFS, we need stop and heal the inflammation resulting from damage to the cartilage.
In both of the courses now available on the ATA site, you will be working to address both of these things using self massage, mobilizations, stretching, kinesiology taping and strength work. Head over to the body map and click on the knee to check them out or drop me an email if you have any questions.
Tomorrow we dive into what happens when these restrictions start to have a rotational compensation (aka pes anserine and IT band irritation).