Muscles of the Hip Joint

0:03 Welcome back to the Movement PhD. I'm Dustin Hardwick, a physical therapist with a PhD in movement science. In this second episode dedicated to the hip, we're going to discuss the muscles that cross the hip joint. On YouTube, you will see slides appearing in sync with the audio. If you're listening on another platform, the visual aids and full transcript are available on my Substack. Whether you prefer listening, watching, or reading, offering all three formats supports better attention and a deeper understanding of the material. Check the episode description for the links. The first motion that we'll talk about is sagittal plane motion. This is probably the most important plane of movement for the hip since it involved in a lot of functional activities. So, think about walking, think about running, ascending stairs. Those are all

0:48 primarily sagittal plane motions. If I were to get out of this chair, that would be primarily a sagittal plane motion as well. So discussing these muscles is is here first because it's the most important groups of muscles. Any muscle that crosses anterior to your hip joint, that's going to be a hip flexor. Any muscle that crosses posterior to that hip joint, that's going to be a hip extensor. So, I put this grab up here with the moment arms for a lot of muscles for a reason to show that not only the muscles we typically associate with hip flexion or hip extension, but also some of our adductors and abductors are involved in that hip flexion and hip extension. I'm going to highlight one important one right now and we'll come back to it again later. Look at the moment arm for this adductor magnus. For those of you

1:34 on audio, that moment arm for that adductor magnus is approximately the same as the rest of those hamstrings. So acting in the sagittal plane, it has just as good of moment arm for hip extension as the muscles we typically associate with hamstrings. So that's the reason for having this image up here. It gives you the line of pull of a lot of muscles that you would might not normally associate with hip flexion or extension. Hip flexion. That's important for things like kicking a ball, for placing a step on a placing your foot on a step as you step up onto stairs, for bringing your leg forward during the gate cycle, whether you're walking or whether you're running. Hip extension. This is the most important movement of the hip. That is our anti-gravity movement. So, every time we are

2:19 standing, those hip extensors are involved in keeping us upright. If I were to get up from this chair, the hip extensor muscles would be the primary muscles involved in that sit to stand propulsing the body forward. So walking that propulsion, some of that is going to come from our hip extension and that's particularly evident if we are climbing stairs or climbing a ramp that requires a lot of torque for hip extension. Let us discuss the hip flexors first. So I'm going to highlight some of the important ones and go through some of them here. Before we do that, let's review the movements into hip flexion. So in open chain hip flexion, you're bringing your femur forward and that femur is free to move because it's open chain. So our pelvis is fixed and we move that femur forward.

3:05 Anterior, that's hip flexion. So think of kicking a ball, doing a high knee activity. Those are open chain hip flexion activities. Closed chain, that's just where we fix the femur onto the ground. So, I'm standing or I'm sitting and I rotate that pelvis forward. So, I tilt that pelvis forward. Whether it's a forward fold where that pelvis tips forward or if I'm sitting here and I just do an anterior pelvic tilt, those are closed chain hip flexion activities. So the muscles involved with that the two most important hip flexors by far is your ilio soaz which remember is a combination of your iliac iliacis muscle which is coming from that iliac fosa and that soaz major what's coming from those lower lumbar vertebraes. So those two

3:50 come together and form this ilio soaz. It is the most important hip flexor because it's a single joint hip flexor meaning it doesn't care what position the knee is in. It's going to produce that torque for hip flexion all the same no matter what that position is. Rectus feorous. This is our most important two joint hip flexor. So it's involved in hip flexion and knee extension which is a really important combination of movement movements for gate. So these are your two primary those two muscles are getting some help from some other muscles like sartorius TFL. Those are two um primary hip flexors but don't contribute quite as much to the torque as iliosus and recam. Adductor longus. Adductor longus is an interesting one and we'll talk about that later. It's a really good hip flexor but only when

4:37 your hip's in extension already. It's not doing a whole lot in neutral but if you're in full hip extension it's a pretty strong hip flexor. Pectinius is kind of the same but it's a smaller muscle so it's not quite as involved in that torque as adductor longus. Then our secondary muscles of hip flexion, adductor brevvis, graascillus. And then the anterior fibers of our glute me and our glute men. They can all contribute a little bit of that hip flexion. As mentioned in the previous slide, iliosoas and rectusorous, those are your two most important hip flexors. So they generate the bulk of the hip flexion torque needed to do functional activities. The difference here being recam is a two-jint hip flexor. Meaning that its length is going to determine how much torque that it can generate. Because of that length tension relationship, it's really doing its most

5:23 torque in that 30 to 70 degrees. So that mid-range of hip flexion at this point, the moment arm is the largest. It has good cross bridging with those sarcimeirs. It's acting as third class lever at this point, meaning that it's really good for getting through that full range of motion. It's contributing a meaningful amount of hip flexion torque in this range. However, when we get to the end range of hip flexion, so 90 to 120 degrees, 80 to 120 degrees, the moment arm of that rec gets really small. It does briefly turn into a secondass lever, which is really the type of lever that generates the most torque, but the moment arm is so small at that point that it's not really doing much for hip flexion. Also, it's short. It's shortened at that point. So, those sarcimeirs are not in their best length

6:09 tension relationship. So your recam is actively contributing the most to hip flexion torque in that 30 to 70°. The iliosus on the other hand, it's a single joint hip flexor. So the length is not going to determine its torque as much because it's going to reside in the best part of that length tension relationship throughout hip flexion. So from the very early ranges of hip flexion all the way through the mid-ranges all the way to end range that ilio so so as maintains a good moment arm for producing hip flexion and that muscle stays within its favorable parts of that length tension relationship. So let's talk a little bit about some takehomes here. Your rec that's a thirdass lever through most of its range of motion as I previously mentioned. So it's optimized for speed and range. torque peaks during that

6:56 mid-range, but then it really falls off as you get to that deep flexion. So, that end range of flexion. But what I didn't mention, and I'll talk more about this in our gate unit, which is this the third part of our hip um unit here, it's a two joint muscle. So, it acts as an energy transfer during gate. And all that means is that during the extension part of the gate cycle, so terminal stands into pre-swing, you're stretching that rectus feorous across both of its joints. So we are loading that muscle with kinetic energy. As we go into initial swing, then we release that kinetic energy and it makes a gate cycle more efficient. So while rectus forous is really only the best as far as a moment arm in that 30 to 70 degrees of

7:41 hip flexion, it's really important in the gate cycle during walking and particularly during sprinting running types of things where we're really loading that rec with that kinetic energy. Iliosas, you can think that think of it as your major hip flexor. It doesn't care the position of the hip, the position of the knee. It's going to produce good amounts of hip flexion torque. One thing to keep in mind about ilio soaz because the soaz part of it is attached to the lumbar spine any torque that's generated into hip flexion you have to stabilize that that lumbar spine to get it and we'll talk about that in that next slide. So those are our clinical pearls and kind of a discussion of ilio soaz versus rectus foras. Let's now talk about the synergistic activity

8:27 of your abdominals and your hip flexors during hip flexion. For a muscle to be able to act upon its distal segment, you have to fix its proximal attachment point. So for all of our hip flexors and primarily primarily those iliosaz rectus feoras, the pelvis and the lower lumbar spine, these are our origins for these muscles. Therefore, if we don't fix that origin and we contract these really powerful hip flexors, it's just going to move that pelvis. So, if I'm laying on my back and I try to do a leg raise and I don't use any abdominals, my leg is not going to lift off the ground because that muscle contraction is just going to pull that pelvis into an anterior pelvic

9:13 tilt because the weight of my legs is much more than the weight of my pelvis. So, we need to first in order to move that hip into hip flexion, we have to first fix that pelvis, fix that lumbar spine through the activation of our abdominals. then those hip flexors can act on that femur and produce that hip flexion that is needed to do this activity. So this is important to think about not just for a lying leg raise. I'm using that as an example because it's the easiest to visualize. You can really think about the origin of those hip flexors being fixed by that pelvis and lumbar spine. But the same thing is true if I'm standing, if I'm taking a step, if I'm walking, running, going upstairs, I have to maintain active contraction of those abdominals in order

9:59 for those hip flexor muscles to do their job. So this is an important basic concept of how movement is organized is we have to fix that origin so that that muscle can act upon that distal segment to produce the functional activity that we're looking to get. And that's again a thing we're going to talk about in the hip part three when we talk about functional activities in gate. We'll talk a lot more about the synergistic activity of the core muscles the abdominals plus the extensors and these hip mus muscles during functional types of activities. The other thing to realize here is if we have any muscle imbalances. So we have a really short hip flexor group. So our iliosaz is short, our rect rectus is short. So

10:45 they're a stiff short muscle. That's going to put some torque on that pelvis and lumbar spine. So if they are stiffer than our abdominals, then just standing or walking, we're going to be in an anterior pelvic tilt. And when we're in an anterior pelvic tilt, that puts our lumbar spine in an excessive amount of lordosis that can put some stress on those lumbar facet joints. So there's an intimate link between your the length of your hip flexors and the health of your lumbar spine and that's because of the synergistic activity between the two. So again, we'll talk about that a little bit in our next episode and we'll talk about that a lot in the lumbar spine unit when we talk about um postural impacts on the health of that lumbar

11:30 spine. Now let's talk about hip extension and those hip extensor muscles that are involved in hip extension. A quick review. Open chain hip extension sagittal plane movement with that femur dis that distal segment femur open to move moving it posterior on that fixed pelvis. That's going to be open chain hip extension. Closed chain hip extension that's going to be a posterior pelvic tilt. So if I'm standing and I lean back, my pelvis is probably going to rotate posterior. That is closed chain hip extension. If I'm sitting in my seat here and I pull in my abdominals and I roll back onto my sacrum, that's going to be another example of a posterior pelvic tilt, which is closed chain hip extension. As me as previously

12:16 mentioned, hip extension is one of the most functionally important movements in the whole body as bipeedal ambulation is what we do as humans and hip extension is involved at all facetses of that. So what are our primary hip extensors? Well, it's our glute max plus our hamstrings. And just remember that adductor magnus, especially those posterior heads fibers, that posterior head of that adductor magnus, that's an important hamstring muscle. So our primary hip extensors, glute max, our single joint hip extensor, and our hamstrings, which are those two joint hip extensors. So there are two other muscles which are secondary in name hip extensors, but one of them is quite important. So our adductor magna's anterior head, it's a little bit more anterior than that posterior head. So

13:02 it's not quite as much of a hippic sensor, but it contributes a little bit. The one that I want to highlight, and I'm going to come back and highlight the glute me posterior fibers throughout this discussion. Those posterior fibers of the glute me, while they're not nearly as large as the fibers involved in extension of our glute max or our hamstrings, those are really functionally important because those posterior fibers of the glute me are the most anti-gravity set of fibers in the body. And we'll talk about that as we move throughout because these posterior fibers are involved in abbuction, external rotation, and extension. Those are all the things that are needed to maintain the body upright during single leg stance. Whether I'm standing on one leg or during the gate cycle where I'm where I have single leg support, those

13:48 glute me posterior fibers need to activate to stabilize that pelvis. Let's talk a little bit about the force couple of our hamstrings and glutes as well as the erectors to control the forward lean of the body. So, the premise here is I'm standing and I lean forward to pick up a box, to pick up a barbell for a deadlift, to pick up my dog, pick up my cat, any of these kind of things. There's a force couple between our glutes, hamstrings, and erectus to produce that motion both on the down, which is the eccentric, and the up. So, what's important to note here is the relative moment arms of these muscles. So, as far as mass goes, your glute max is the most important hip extensor. However, its moment arm falls off pretty

14:34 rapidly as I go from 15 degrees of hip flexion down to 75 90 degrees of hip flexion during that eentric um hip extension activity of those extensors. It's eccentric because I'm leaning forward which is hip flexion but the muscles that are supporting it are our extensors, our hip extensors. So as we go from standing to forward fold that glute max is progressively getting a smaller moment arm and the opposite is happening with those hamstrings. So hamstrings being the squares here which are higher than the glute max and they increase as we go from more upright to a more forward fold. We see the hamstring moment arm get better. What's also interesting is our adductor magnus here

15:21 which is this triangle. Its moment arm is greater than that of the hamstrings. So that's why I say adductor magnus is essentially a hamstring muscle because its moment arm from hip hip extension is better than any of the other hips hip extensors. So let's review that real quick. As we go from upright to forward fold, our glute max decreases its moment arm. So the reliance on glute max goes down and we see an increase in the moment arm for those hamstrings muscles. So, if I'm doing an eccentric RDL or Romanian deadlift, it's a lot of glute max towards the standing part and you're progressively getting more hamstrings as we get further towards the ground in that RDL. The force couple here with erector spine A, those erector spina have to activate isomemmetrically to

16:07 keep your spine in place. Otherwise, you're just going to flex through that lumbar spine, which is not good for that disc, and it's not good for generating torque for that for picking up your dog, picking up your kid, picking up that barbell. So, we have to synergistically activate erector plus glute max plus hamstrings. Next, let's talk about the force couple involved in pelvic tilts. So, anterior pelvic tilt at the hip, that's closed chain hip flexion. Posterior pelvic tilt and at the hip joint, that is closed chain hip extension. So, taking a deeper look here at the anterior pelvic tilt. So, an anterior pelvic tilt, you have your ASIS or the anterior part of your pelvis moving inferior as we rotate anterior. And that psis, that sacrum, they're all

16:54 going to go superior. So, that's that anterior pelvic tilt. What are the muscles involved in anterior pelvic tilt? Well, the most important ones are your hip flexors on the anterior aspect because they're going to be pulling through that asis from sartorius from that aiis from your rec from the iliac fosa and from those lower lumbar spinal segments from your ilio soaz. So, it's a combination of those hip flexors on the anterior aspect and those erector spina muscles on that posterior because they're going to be pulling through that sacrum and pulling it superior together. These are going to combine to make that anterior pelvic tilt of that pelvis. So, let's expand this concept a little bit. If the motion of an anterior pelvic tilt

17:40 is because of activation of your erector spine a plus your hip flexors. If somebody is standing in a posture of excess anterior pelvic tilt. So it looks like they're sticking their their glutes out. They have a increased lordosis in that lumbar spine. It looks like their abdominals are extended a little bit. That happens because there is shortness or stiffness of those hip flexors and that erector spine. Okay. It also means that those abdominals which are involved in the other side of it are not doing their job. So an excess anterior pelvic tilt that's a result of shortness of sartorius rect ilioaz and erectorpina and inadequate activation of your abdominals and possibly those hip extensors.

18:27 Now let's talk about the force couple involved in a posterior pelvic tilt which is the opposite of this. So in a posterior pelvic tilt, our psis and our posterior aspect of our pelvis is going inferior and our asis, pubic crest, all of those anterior parts of our pelvis, those are going to be going superior. So what are the muscles involved in a posterior pelvic tilt? Primarily, it's your abdominals. So rectus abdominis, all of your obliques through their attachment to that pubic crest, through that iliac crest, they're going to be the muscles primarily involved in that posterior pelvic tilt. They're going to get some assistance on the back end from your glute max and your hamstrings. So again, posterior pelvic tilt, that's a force couple of your abdominals and your

19:12 hip extensors. So if somebody has a postural fault of a posterior pelvic tilt, then one can guess that most likely their hamstrings and glute might be short or stiff as well as shortness or stiffness of that rectus abdominis. Now there are some nuances here with this posterior pelvic tilt where the rectus abdominis might not be short and we'll talk about some of those different postures in our lumbar spine unit. But for now, just recognize a force couple. recognize in a postural fault of a posterior pelvic tilt. Probably some shortness of your hamstrings, glute might be some shortness of that rectus abdominis. The next plane of motion here is our frontal plane. So remember our frontal plane divides our body into a front and a back half and we have an AP

19:57 axis for that frontal plane. Any muscle that crosses laterally or superior to that hip joint, those are going to be abductors. Any muscle that crosses inferior or medial to that hip joint, those are going to be aductors. So this graph here shows some of our primary abductors. So glute me, glute men, TFL, purapiforis in some parts of its range are abductors. Muscles like adductor longus, um adductor magnus, those are your primary adductors. Also your biceps forous that has a little bit of a moment arm for for aduction. Adductors they are not as functional in the frontal plane. There are some lateral movements where adduction is important. Your adductors

20:43 are actually more important for stabilizing the hip joint. So co-contracting with those abductors to stabilize the pelvis in that frontal plane. And also many of the adductors are involved in sagittal plane motion. We already talked about adductor magnus and we'll talked about how adductor longus is important for that as well. Our abductors are one of the most important groups of muscles in the lower extremity and especially at the hip joint because they control that pelvis in that frontal plane. So every time I'm standing on one leg, the abductors of that leg have to activate to keep my pelvis stable. So it makes them really important for functional activities like walking, stairs, lunges, all those kind of things. First, let's talk about the adductor group. So those muscles

21:28 involved in hip adduction. So a quick review. Open chain hip adduction. It's moving that femur towards midline when that pelvis is fixed. So that's open chain because the distal segment is free to move. If I move that leg towards midline, that's hip aduction. Closed chain. So if I'm standing on my right leg and I drop my opposite pelvis, so I drop my left pelvis, that is closed chain aduction. If you need a review of that closed chain movements, those arthrokinematics, make sure you see the previous video which is looking at the bony anatomy and osteo and arthrokinematics. I spend quite a bit of time discussing closed chain movements of the hip. So our primary hip

22:14 adductors, well that's all of our adductor groups. Pectaneous graascilus adductor longus brevis and magnus. Our secondary hip adductors biceps feorous the long head and the very posterior fibers of that glute max. These are pretty small moment arms for hip adduction. So they're not really contributing a whole lot there. And then our optator and quadratus morris. They have a smaller they're smaller muscles without as much torque. Primarily it's those adductor groups. It's a large group of muscles and they they do most of the torque for that hip added duction. Let's talk about how the adductors muscles work together to produce a sideep type of motion. So this could be kicking a ball laterally from the opposite foot. It could be crossing over during a lateral movement of the

23:01 body. So in this case we have our stance leg um adductor group acting on the pelvis in closed chain by pulling that pelvis towards it. So dropping that other hip down and then we have the adductor group on the other leg which is moving that now free femur on the other leg the kicking leg into adduction. So you're getting activation of both sides of the adductors or the adductors from both legs to produce this crossover kick or a crossover um ambulation type of activity. I've talked extensively so far about how your adductor magnus is a hip extensor and is primarily a hamstring muscle. Now let's talk a little bit about the adductor longest. Now the

23:48 adductor longus is a very interesting muscle. So it's an adductor. So, it's involved in any motion that involves a deduction, but it's also a hip flexor and a hip extensor. So, you're probably thinking, how can one muscle be a hip flexor as well as a hip extensor? Those are opposite motions. Well, your adductor longus is a hip flexor from full hip extension. And so if I'm in full hip extension, so the trailing leg when I'm sprinting, right, as it's transitioning from a stance leg to a to a swing leg, so pre-swing into initial swing, your adductor longus is a really important hip flexor. So it's going to activate during that pre-swing to slow that limb down. So it's going to activate eccentrically as a hip flexor

24:33 at that point. And then it's going to activate concentrically to start to swing that leg forward. So, in the extremes of hip extension, your adductor longus is a really important hip flexor. In the extremes of hip flexion, so now I've just got done from swing and now I'm transitioning back to stance. So, I'm in terminal swing into that initial contact. My adductor longus is really going to help slow that limb down. So, it's going to be an eccentric hip extensor and then a powerful concentric hip extensor. So your adductor longus is a hip flexor from hip extension and a hip extensor from hip flexor. So that makes it a really interesting muscle. And if you want to prove this to yourself, and I only I encourage you to

25:19 only do this if you are used to sprinting and you're healthy enough to do a sprinting workout. Go do a 20x 20 or a 10x40 sprinting workout. You'll note that your the insides of your leg, that adductor muscle group, they're going to be extremely sore, which is odd, right? Sprinting is not an adduction type of activity. It's because of that activity of that adductor longus as well as that adductor magnus for the extension part. That eenter control and turning that leg around in both of those extremes that puts a lot of stress on that adductor longus. And I guarantee you'll feel that the next day. Moving on to hip abduction and those hip abductor muscles. So, a review of the motions. Hip open chain abduction. We're fixing our pelvis and we're moving that leg

26:05 away from midline. So, any movement away from midline is abduction. So, moving that femur away from midline is hip abduction. Closed chain. I'm going to be standing on my right leg. If I'm talking about right clos hip abduction and I'm going to hike my left pelvis. So hiking of that left pelvis, that opposite pelvis, that is hip abduction, closed chain on that stance leg. So what are the muscles that mediate this hip abduction? The most important hip abductor is your glutius medius. It represents about 60% of all the muscle fibers that are involved in hip abduction. And those posterior fibers of the glute meat are some of the most important anti-gravity muscles in the body. Glute men, it does a lot of the

26:51 same things as glute me. It's just a lot smaller so it doesn't generate near as much torque as that glute me. And then we have TFL tensor fascelata. It is a hip abductor but also has some movement at the knee and it's also an internal rotator. We'll talk about this one as well. This one we don't like as much as that glute meat. Our secondary hip abductors. Purformis is an abductor in certain parts of its range. Sartorius is a hip abductor, but because it crosses so many different planes, it's not the most powerful hip abductor. And then your recim has a very small moment arm for hip abduction. Now, let's talk specifically about that glutius medius. Again, it's the most potent abductor. It accounts for 60% of the cross-sectional area of muscles that abduct the hip. And

27:38 what's interesting and what's really important about our glutius medius, it has three functional subdivisions or three heads of that glutius medius. So our anterior portion, it's probably the smallest part of that glutius medius. It's involved in hip abduction, hip flexion, and hip internal rotation. The middle fibers of that glutius medius, those are pure abductors, and they produce most of the torque in abduction for the for that hip joint itself. the posterior fibers of glutius medius. This is the most important, I'm just gonna say it, the most important fibers of the lower extremity because it's involved in every aspect of anti-gravity activity. When we're standing on one leg, it's an

28:24 abuctor which supports the limb in that frontal plane. It's an extensor. When you're standing on one leg, those activation of those fibers are really important for maintaining that extension. So, they're helping out that glute max, those hamstrings, and it's an external rotator. That's the important thing as well. That abduction and external rotator in closed chain are what makes it so important because when you're standing on one leg, gravity is trying to pull you into adduction, flexion, and internal rotation. The only muscle that can counteract all of those forces are is the posterior fibers of that glutius medius. Let me say that one more time. The only fibers in the lower extremity that can counteract gravity when you're standing on one leg is the

29:10 posterior fibers of that glutius medius. So that is why I will always say this is the import most important fibers in that lower extremity for healthy movement, healthy anti-gravity movement such as gate, stairs, running, all those kind of things. Let's talk about frontal plane stability of that pelvis. So your abductors act as a first class le lever in supporting that pelvis in that frontal plane. So let's look at this. We have our body weight on one end. The center of mass of our head, arms and trunk. So that hat is a basically at the level of the belly button just a little bit inferior to that depending on your anatomy. The fulcrum here is your hip joint which is right here a little bit lateral to that

29:57 body weight. And then the effort arm is your abductor. So mostly that glute me. So whenever you have a fulcrum in between the effort which is our hip abductors and the resistance our body weight that makes it a first class lever that's a system that's designed for balance. That allows our hip abductors to support ourselves in single leg stance and not have to generate massive amount of torque like our glute max does in the sagittal plate. We've talked about glutius medius. Those posterior fibers are our favorite muscle in the lower extremity. The TFL, I don't want to say it's our least favorite, but it is one that causes a lot of issues at the hip, at the knee, and down the chain to the ankle. So, it's a relatively small muscle. It's probably only

30:43 approximately 10% of the cross-sectional area of our abductors. It's a hip abductor. It's an internal rotator and a flexor. It also has some actions at the knee. So, it can laterally rotate the tibia through the knee joint and it can flex the knee. So, the reason why this muscle often is a problem is because it attaches to this IT band. Because it attaches to this IT band, if you have any shortness or overactivation of that TFL, it puts a lot of tension through that IT band. And tension through that IT band can cause compression of that bersa on that lateral hip. It can cause compression to that bersa on that lateral knee. The IT band is also attached to the patella and it pulls that patella patella laterally and

31:29 pulling that patella laterally will cause it to compress against the lateral condile of that femur. So if you have any kind of patellofhemeral things your IT band is related to that as well. So even though the TFL is a relatively small muscle, if we have any kind of poor activation of our glute me or glute men, that TFL tries to take over and because of that we start to get that rubbing at the hip joint, at the knee joint. We get some delofhemeral tracking issues. Can also lead to some issues down the chain because that TFL is an internal rotator. So if we start to internally rotate that femur too much, it starts to then drive that down the chain as well. So we'll get some pronation at the ankle. We get too much

32:14 rotation at that knee joint. That puts stress on the menisci and those ligaments of that knee joint itself. So overactivation of TFL can be a rather problematic type of thing across multiple segments of that lower extremity. And we'll talk quite a bit about this in our knee unit. And we'll bring it back for the ankle unit as well. Going to move on to our last plane, that horizontal plane. Now, so any muscle that crosses anterior to that hip joint, that's going to be an internal rotator. Any muscle that crosses posterior to that hip joint, that's going to be an external rotator. So they produce rotary torque on the femur. They also stabilize the pelvis in that transverse plane which is their

33:01 most functioning relevant thing that the external rotator group does. Let's talk about the hip external rotator group first. So a review of our motions open chain hip external rotation transverse plane motion moving that leg rotating that leg out. So rotating that leg away from midline that's going to be open chain external rotation. In closed chain, if I'm standing on my right leg and I send my left side of my pelvis posterior, that's going to be closed chain hip external rotation. Similarly, if I plant on my right leg and I turn away from that planted right leg as I'm going to catch a ball over my left shoulder or reach over my left shoulder,

33:47 that's going to also be closed chain external rotation of the hip. So the primary muscles involved in hip external rotation glute max very large muscle largest muscle in the body as far as cross-sectional area purapiforis perfect line of motion for external rotation um then your opterrator um gli quadrus group those are your intrinsic hip external rotators secondary we have biceps morris long head sartorius again an external rotator and abductor opterrator externist posterior fibers of glute me minimus and glute me posterior fibers. I kind of hate that the glute me posterior fibers are listed as a secondary hip external

34:33 rotator because in closed chain they're really important for counteracting gravity. So gravity is trying to put that hip into flexion aduction and internal rotation. The glute me posterior fibers are perfectly aligned to counteract that and those posterior fibers are good external rotators in closed chain. Let's talk about the force couple of your retor spine A and your hip external rotators for turning away on a planted foot. So again I run and I plant on my right foot and I turn to my left. So that act of turning to my left on a right planted foot involves that external rotator group. So glute max posterior fibers of glute me papformis

35:19 plus the erectorpina group on the left side because your erector spina are ipsolateral rotators. So what happens if we don't have strength in those external rotators? So the posterior fibers of that glute me that glute max they're not doing their job. So what's going to happen is you're going to get vgus at that knee because your femur is going to go into aduction and internal rotation. And with that internal rotation and aduction, we get a big increase in that Q angle at that knee joint. That's going to put stress on that lateral hip because that IT band is going to be pulled taut across it. It's going to put some rotation at the knee itself. So that's going to put stress on that meniscus, all those ligaments. It's

36:06 going to increase that bow stringing effect of your quads plus your IT band on that patella. It's going to pull that patella laterally which is going to increase the compression between the patella and that lateral femoral condile. And if you look down the chain, you can see how this position affects the tibia. That lateral tibial rotation is now going to drive that arch into the floor. So you're going to get a flattening of that arch. So when you're in this position, it puts stress on pretty much every joint of the lower extremity. And really the only muscle that can straighten this out and take it from this collapsed position to a normal position, posterior fibers of that glute me. So if you ask me what my favorite muscle of the lower extremity is, it's that posterior fibers of that glute me.

36:53 It fixes a a lot of the issues that you're going to have at that lower extremity. Finally, let's talk about our hip internal rotators. And let's first review the motion of hip internal rotation. So in open chain, we fix the pelvis and we rotate that leg in that transverse plane towards midline. That's open chain internal rotation. Closed chain, I'm planted on my right leg and I move that left pelvis forward. So bringing that left pelvis forward is closed chain internal rotation on the stance right leg. So there are no primary internal rotators of the hip. There's no muscle that's its only job is to do internal rotation of the hip. It's all a secondary action of a different muscle. So what are those muscles? Glute

37:39 meat and glute miner fibers. Probably the most important internal rotator is the TFL. Then you have some internal rotation from a lot of your adductor group here. So I started TFL because it in weight bearing it's your primary internal rotator. In the previous slide, I talked about all the things that go wrong when your TFL is overactivated, but it's actually an important functional muscle for gate because it's the muscle that's primary primarily related to bringing the pelvis forward during the gate cycle. So, if I'm planted on my right leg and I need to bring that left hip forward, that TFL is the muscle that's doing that closed chain internal rotation. So, it's not always a bad thing. your TFL has a functionally relevant action and that's

38:25 to bring the pelvis forward during that gate cycle. Let's end with a review of the relative torque of the hip muscles and what that means for function. I don't expect you to memorize or know the absolute torque for any of these groups of muscles. Really, I want you to appreciate the relative torque when looking across them. And not only that, why why does the extensors have the greatest amount of torque? because they're the most anti-gravity muscles in the lower extremity. So, anytime I get up from a seat, get up from a chair, get up from a squat, I need a lot of hip extension torque. Anytime I'm standing, they're what's holding me upright. If I climb stairs, climb a ramp, those extensors need to push my whole body weight up that ramp or those stairs. Hip flexors, they need quite a bit of

39:12 torque, too. Anytime I am bringing my leg forward against gravity, I'm doing a high knee. I I need to place my foot on the next step. I need quite a bit of torque because your legs weigh quite a bit. So, you need those hip flexors to be able to activate to pick up that leg to put it on a step. If I'm laying down in a bed and I need to put my legs over the edge of the bed, I need to lift them against gravity and and swing them over. So, I need quite a bit of torque from those hip flexors. Our hip aductors, this is a surprising one, right? they they can generate quite a bit of torque, but remember they're involved in a lot of sagittal plane motions that adductor magnus and then that for hip extension that adductor longus for both hip flexion and extension. So there's quite a bit of torque there for your aductors. They also generate quite a bit of torque

39:58 to stabilize the pelvis in that frontal plane. So co-contraction with those abductors, your abductors have a medium amount of torque generating capabilities. They have a really important role for that anti-gravity frontal plane support of the pelvis. But remember, they get that balance afforded by a first class lever. So they don't need as much torque to maintain that anti-gravity control as say our extensors, which all are going to act as a thirdass lever to produce that extension of that hip. And finally, our internal rotators and external rotators. They're going to have the least amount of torque because they're usually not working as much against gravity, right? So transverse plane is cutting across the plane of gravity. So they they don't need to support the entire weight of the

40:44 body against gravity. So that's a quick review of the relative torque between our extensors and flexors, our sagittal plane motion, our aductors, abductors, our frontal plane muscles, and our horizontal plane internal and external rotators. Thank you for joining me for this second part of our hip unit. Today we review the muscles that cross a hip joint and their actions in each of the planes of movement. If you found this helpful, please subscribe to the podcast and follow me on social media. If you have any questions or any specific topics you would like to see covered, let me know in the comments. In our next episode, we will continue our hip unit by discussing the importance of the hip or gate and functional activities. Thanks again for listening and I'll see you in the next episode.