Anatomy For Runners: The Knee

Welcome to my Anatomy For Runners series! With this I’m hoping to educate runners on their bodies so that they feel more empowered in staying healthy. Don’t worry, we’ll keep it light, fun, and focused on what you really need to know with a bias toward the runner’s body.

This second installment is all about the knee. So, you could say, we’re going to go over everything you “kneed” to know about this joint and why Aunt Margie is wrong when she says you’re going to ruin your knees as a runner.

The knee joint is classically known as a “hinge joint”, meaning that it moves in two directions, similar to a hinge on a door. There is a tiny bit of rotation that occurs here as well, and as we’ll learn in the coming paragraphs, it’s important to be able to control that rotation as the miles pile up.

The knee is the interface where the femur and tibia meet. The fibula is adjacent to the tibia, but does not articulate with the femur in the way the tibia does. Both the tibia and femur are cushioned with cartilage - a dense connective tissue that helps with shock absorption. On top of the tibial cartilage sits the meniscus, a structure many of you may be familiar with. The meniscus helps improve the fit of the joint and guides movement. There are two aspects of the meniscus, the medial (inner) and lateral (outer) portion. The bones of the knee joint are connected together by several ligaments, which we won’t get into much detail about, as they are not commonly injured in runners unless a trail or obstacles are involved. The patella, or knee cap, has no direct articulation with another bone and is both held in place and influenced by the quadriceps. The four muscles form a common tendon that attaches to the top of the patella, and then progresses to create the patellar tendon (you know, the tendon that your doctor hits with the reflex hammer). Finally, the knee joint is surrounded by a capsule which is a connective tissue that wraps around it sort of like Saran wrap.

The meniscus is of particular interest because there are incidences of chronic meniscal tears in runners, usually due to repetitive rotation of the joint. Knee rotation is controlled largely by the hips (yes, here’s another reason to do your hip strengthening exercises) and hamstrings. The medial meniscus is 5 times more likely to be injured than the lateral mensicus, because of its shape and biomechanical function. At this point, I think it is beneficial to note that there is a lot of misinformation out there about meniscus surgery, specifically that surgery is the only thing that can “fix” it. Studies(1) have shown that with a proper rehab and PT program, meniscal injuries can resolve in a similar timeline compared to those who elect to have surgery.

Now let’s dive into the muscles that cross the knee joint, shall we? The quadriceps are a group of four muscles located in the front of the thigh and have the ability to straighten the knee. The quads are also the muscle group that controls knee bend in running, so this is why Boston Marathon runners often have debilitating soreness of their legs after the race - the ~13 miles of steep downhill requires this controlling contraction of the quadriceps. Also of note is the IT (acronym for iliotibial - describing its attachments on the hip and tibia) band, which is actually a very, VERY thick band of fascia that overlays the lateral (outer) quad muscle and eventually attaches on the tibia, thus crossing the knee joint.

Next there are the hamstrings, which are located in the back of the thigh. There are 3 hamstring muscles, the Semitendinosus and Semimembranosus located more medially (toward the inside) and biceps femoris located more laterally (toward the outside). The hamstrings apply a braking force with each step and then help transition from midstance (the “downstep”) to terminal stance, right before the foot leaves the ground. The hamstrings attach to the back of the tibia and fibula and originate from a common tendon up near the sit bone (you know all about this if you’ve had a high hamstring strain). Lastly, we’ll discuss the adductors that cross the knee joint: the Gracilis and Adductor longus. These muscles lend stability to the inside part of the knee and provide stability.

Okay, so let’s address your family’s concern about ruining your knees through running. Dr. Ryan wrote a blog about two studies that demonstrate little to no differences in knee health between those who run and those who don’t. In other words, there is no direct correlation between knee arthritis and running. Take that, Aunt Margie.

Thanks for join(t)ing us on this anatomical journey!

Keep going, you got this!

Dr. Kacy Seynders

Sources:

1. Erik Hohmann, Vaida Glatt, Kevin Tetsworth, Mark Cote,

Arthroscopic Partial Meniscectomy Versus Physical Therapy for Degenerative Meniscus Lesions: How Robust Is the Current Evidence? A Critical Systematic Review and Qualitative Synthesis,

Arthroscopy: The Journal of Arthroscopic & Related Surgery,

Volume 34, Issue 9,

2018,