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.
The hip joint is a ball and socket joint, with the “ball” being the head of the femur (thigh bone) and the “socket” being the acetabulum of the pelvis. There is cartilage on both of these surfaces that help to cushion the joint, as well as the labrum, which is a cartilaginous ring that improves the fit of the joint. I’m not much of a handywoman, but I’ve heard the purpose of the labrum is similar to that of a washer in the DIY world.
Chronic labral tears are quite common among distance runners. They are often caused by an imbalance of muscular tension and strength among the myriad of muscles that surround the hip joint that causes the head of the femur to bump up against the edges of the labrum, however can also simply be from repetitive use.
There is an increase in risk for labral tears in people with abnormal anatomical fit of the joint, termed hip impingement. There are two broad types of hip impingement: CAM and Pincer. CAM is where the “Ball” of the femur is too big for the “socket” of the acetabulum, and vice versa for Pincer, where the acetabulum is too deep for the head of the femur. As you can see, this can lead to repetitive stress on the labrum as it gets “caught” in the poor fit of the joint.
The muscles of the hip can get pretty complicated, but I’ll try to break it down as simply as I can. There are four major muscle groups located here: the hamstrings, quadriceps, adductors, and glutes. The hip joint is also influenced by muscles that have attachments on the spine and pelvis, such as the abdominals, pelvic floor, iliopsoas, and quadratus lumborum. Also important to note, are the deep rotators, Tensor Fascia Latae (TFL), and piriformis (Also a hip rotator).
The Quadriceps extend (straighten) the knee and have attachments on the femur. One of the quad muscles - the rectus femoris - crosses both the hip and knee joint and is one of the hip flexors, along with the pectineus (adductor group) and iliopsoas. It is often responsible for anterior pelvic tilt and highly influences pelvic posture. The quads help control the knee with each step before assisting with forward propulsion.
The Hamstrings are located on the back of the thigh, spanning from the sit bone (ischial tuberosity and across the knee joint to attach on the shin bone (tibia). The hamstrings bend the knee and assist in extending the hip. In running gait, they help to decelerate and brake the force of each step, and this muscular action is what makes this muscle group susceptible to tendonitis. There can be both high (proximal) and low (distal) hamstring tendinitis.
The Adductors are located on the inside portion of the thigh. They have attachments on the pubic bone and then span various distances, with some muscles attaching on the femur and others crossing the knee to the tibia. Their primary role is to bring the leg closer to midline, but in running gait they serve as more of a stabilizer and control rotation of the femur. A common injury here is a “sports hernia”, or a strain of the adductors and/or adductor tendon. The name is a misnomer because there is no involvement of the viscera as there is with the more “traditional” hernia.
Last, but certainly not least, is the Glute muscle group. This one hardly needs any introduction, but what’s important to note is that there are three glute muscles: Gluteus maximus, Gluteus medius, and Gluteus minimus. They all have similar functions with small nuances between the three. The glute max extends and externally rotates the hip and is the big powerhouse for forward propulsion. The glute med abducts the hip (brings the thigh away from midline) and is important for pelvic stabilization while standing on one foot. Weakness here often causes the infamous “hip drop” seen in many gait analyses. The Gluteus minimus is the smallest of the three and assists in hip abduction and internal (inward) rotation. You’ve probably heard that strong hips are important for injury prevention, and it is absolutely true. Make sure you strengthen your glutes in a functional position, which for runners is standing on one leg!
This concludes the "hippest" blog of them all. We’ll talk about some other relevant anatomy of this region when we cover the core and lower back. Stay tuned for the next installation!
Keep going, you got this!
Dr. Kacy Seynders, PT, DPT, OCS