By Gavin Buehler
A few years ago, I posted a video titled "How To Strengthen Your Medial (Inner) Hamstrings.” I recently received a question posted in the comments on this video asking if strengthening the medial hamstrings could help with an externally rotated tibia and a supinated foot? The short answer is yes, it could have some impact on this type of presentation and possibly help a little. However, there are many other considerations with regard to tibial external rotation. This presentation likely stems from greater contributions coming from the hip and core rather than the compensatory results at the knee. So, I decided to unpack this question and explain in more detail as I do see this sort of presentation frequently, and understanding how the alignment of this chain works can help alleviate issues at the hip, knee, ankle and or foot. I will also explain the terms of supination and pronation as they apply to the foot as I do find people misuse them as they can be confusing with feet. An external rotation at the tibia usually causes over pronation in the foot.
The accompanying video below offers more visual references.
Let’s jump into part one of this two-part series.
What is an externally rotated tibia?
Your lower leg (below the knee) has two bones. The fibula which is the smaller bone on the outside, and the tibia, which is the larger shin bone that bears the majority of loading. A tibia that is externally rotated faces out and away from your centerline in relation to how it is stacked under your femur (thigh bone). A common way to tell if this alignment is off is by finding the bottom edge point of your patella (kneecap), and the tibial tuberosity which is the boney prominence just under the kneecap on the shin bone. These two points should be fairly aligned with one another. With an externally rotated tibia, the tibial tuberosity will be out of alignment and offset to the outside of the bottom edge of the kneecap.
What is a pronated foot, versus a supinated foot?
This gets confusing because many people associate how their foot is rotated due to the rotation from the hip or even the knee or ankle joints to be the orientation of the foot. However, pronation and supination are terms used to describe movement that occurs in the foot itself at the subtalar joint, rather than what is happening from the leg. But how the ankle stacks above that joint will usually cause a compensatory position at the subtalar joint. So, if your foot turns out like a duck, that’s external rotation that could be coming from the hip, knee or ankle. It’s not a supinated foot. In fact, this presentation usually causes pronation in the foot. (Note: to make things even more confusing, external rotation at the ankle joint is actually called abduction and internal rotation is adduction.)
Pronation or supination of the foot is a combination of the three cardinal planes of movement at the subtalar joint. This video here gives a great explanation for clarification. For now, pronation of the foot usually looks like a flattened arch and is common when the ankle appears kinked in.
Supination presents as a high foot arch and is common when the ankle appears kinked out.
Why does the tibia externally rotate?
When a tibia is externally rotated, you will commonly find the femur (thigh bone) internally rotated, causing the tibia to externally rotate as a compensation. This will often make the knee look kinked in (valgus) or knock kneed. The external rotation of the tibia causes the kink in (valgus) at the ankle which causes over pronation of the foot. When things aren’t stacking under optimal alignment for proper weight distribution, our bodies will compensate joint to joint to distribute the load so that we can remain upright or balanced in whatever position we are trying to maintain.
How does strengthening the medial hamstrings help?
There are three hamstring tracts on the back of your thigh. All of them cross both the hip and knee joints. But their attachment points differ and as a result they each have a different impact on our structure.
Biceps Femoris
The biceps femoris is the outer most hamstring and actually has two muscle
heads. Only the long head crosses the hip joint starting at lateral aspect of the ischial tuberosity (outer angle of the sit bone). The short head starts on the linea aspera of the thigh bone (ridge on the back to the thigh bone). Both heads then cross the outside portion of knee joint attaching to the fibula bone. This line of pull can actually cause external rotation of the tibia, and often this hamstring is often more dominant and tighter in many individuals.
Semitendinosus & Semimembranosus
The semitendinosus starts from the ischial tuberosity just to the inside of where the biceps femoris attaches, crossing the hip joint and travelling down the back of the thigh crossing the inner portion of the knee joint attaching to the upper inside end of the tibia. The semimembranosus follows a very similar line to the semitendinosus starting from the ischial tuberosity just to the inside of the semitendinosus travelling down the back and inner portion of the thigh crossing the inner portion of the knee joint and also attaching to the upper inside end of the tibia. The line of pull from these two muscles can help internally rotate the tibia, and often these muscles are found to be weaker and over stretched.
The biceps femoris crossing the outside of the knee helps provide support and stability to the lateral aspect of the joint, while the semitendinosus and semimembranosus crossing the inside portion of the knee joint provide support and stability to the medial aspect of the knee joint. These two muscles attaching to the tibia itself which is the load bearing bone of the lower leg are especially important for assisting with structural alignment due to their attachments and lines of tension. I explain some of this here in this video.
Given what we’ve learned above, we can see how creating balance between the biceps femoris and semitendinosus and semimembranosus muscles can help with the rotation and alignment of the tibia. By strengthening the weaker medial hamstring muscles, we can reduce torsion at the knee joint reducing wear and providing better alignment both up and down the chain for reduced stress on joints during load bearing activities.
This is a localized look at what might be happening with the presentation from the original question. In part two of this installment, we’ll expand our perspective and take a look at what might be occurring through the hip and core that may be more of a root cause to this issue.
Hopefully you found this information helpful!
As always, these videos are for entertainment and educational purposes only. Please consult a health professional before attempting new exercises or protocols, as the following suggestions may or may not be appropriate for you.