Next up to bat in the posture guide series is Knocked Knees, or Knee Valgus.
Knocked Knees (Genu Valgum) are defined as: “The knees are tilted toward the midline. Legs curve inwardly so that the knees are closer together than normal.”
Weak hips, particularly the abductors, usually get the blame for this problem, but it is so much more than that. Allow me to explain.
I will be covering:
- How knocked knees develop
- Consequences of knocked knees
- What can be done
TL;DR: Knocked knees are a result of the body trying to find joint actions it is naturally missing in order to complete the gait cycle, or allow for full human movement. This comes at a cost of stressing tissues and joints around the pelvis and knee. To fix it, we should start with the root of the problem – the pelvis in Anteiror Tilt.
HOW KNOCKED KNEES DEVELOP
To understand this issue, let’s begin (as I always do) at the pelvis. There is a concept known as “Q-Angle”, which basically is the angle the top of your leg bone (femur) makes with the bottom of femur.
In theory, the larger this angle, the higher chance of knocked knees. But why is this angle there to begin with?
Usually it starts with a genetic predisposition. Many people, espeically those with a more “narrow” frame, have a pelvis that is wider at the top (pelvic inlet) and more narrow at the bottom (pelvic outlet).
This biases the pelvis towards the joint actions of:
- External Rotation
It’s important to appreciate that the femur will follow the pelvis. Imagine the pelvis as the lead in a swing dance and the femur as the follow. The pelvis will dictate what the femur can and will do.
If the pelvis is biased towards external rotation, the femur will as well. Notice in this alignment how the femur slides forward in the hip socket, causing the lower shaft to come inward. This is femoral external rotation in a resting orientation, or neutral posture.
Since both internal and external rotation are necessary for human movement, the body tends to compensate to find the joint action it is needing, but cannot find.
This means that the pelvis tends to come forward in an Anterior Pelvic Tilt. This causes the femurs to go into internal rotation.
From there, the tibias go into tibial external rotation, in which you get the classic knocked knees.
CONSEQUENCES OF KNOCKED KNEES
Obviously this presentation is not ideal.
the tensional stress placed on the MCL and adjacent capsule may weaken the tissue., excessive valgus of the knee may negatively affect patellofemoral joint tracking and create additional stress on the ACL.
Standing with a valgus deformity of approximately 10 degrees greater than normal directs most of the joint compression force to the lateral joint compartment.
This is because it creates a “bowstring” like pull on the kneecap, pulling it laterally and increasing stress on the joint.
A study by Maclntyre et. al, 2008 compared patellar mechanics between those with no pain & those with anterior knee pain.
They found that 𝐭𝐡𝐞 𝐩𝐚𝐢𝐧𝐟𝐮𝐥 𝐠𝐫𝐨𝐮𝐩 𝐬𝐡𝐨𝐰𝐞𝐝 𝐚 𝐬𝐭𝐚𝐭𝐢𝐬𝐭𝐢𝐜𝐚𝐥𝐥𝐲 𝐠𝐫𝐞𝐚𝐭𝐞𝐫 𝐥𝐚𝐭𝐞𝐫𝐚𝐥 𝐬𝐡𝐢𝐟𝐭 𝐨𝐟 𝐭𝐡𝐞 𝐩𝐚𝐭𝐞𝐥𝐥𝐚.
The wider the pelvis and the more external rotation present, the wider the lateral “bowstring” force pulling the patella to the outside (Kernozek et. al, 2008).
There is a plethora of evidence suggesting females experience a greater incidence of abnormal mechanics & related pathologies of the patellafemoral joint than males (Fithian et. al, 2004; Powers et. al, 2002), which coincides with what I said earlier about people with more “narrow” frames being predisposed to this issue.
This is likely also a factor in why females experience more ACL tears than males.
Interestingly enough, weakness of the muscles that help prevent knees collapsing are particularly weak in otherwise normal & healthy females (Boling et. al, 2002.)
WHAT CAN BE DONE?
Let me make something clear to help provide some hope to those who have this: The degree to which the visual presentation of knocked knees clears up can vary from individual to individual.
Factors like age and how long you’ve had this issue can determine how much “better” they look over time, but that is significantly less important than the movement capabilities your pelvis and legs possess.
What I mean by that is if you have a slight degree of knocked knees, but you have full access to internal/external rotation, adduction/adduction, and flexion/extension, you’re probably going to be okay.