Anatomy of the hip joint

Chapters:

Watch video only

Introduction0:00–0:16

If you have ever wanted to know about the new ‘hip joint’ in town, look no further than the hip joint! The hip joint is a large, strong joint connecting the pelvis to the lower limb.
Let's take a closer look! The hip joint is a synovial ball and socket joint, where the head of the femur forms approximately two thirds of a sphere, and it articulates with the cup-like acetabulum of the hip bone.

Articulations0:16–1:54

The femoral head is not entirely round, as it has depression on top of it which is called the fovea for the ligament of the head of the femur.
Except for the fovea, the femoral head is also covered entirely in articular cartilage which facilitates smooth movement and prevents bone erosion as it slides within the acetabulum.The acetabulum, on the other hand, is a bowl like structure on the lateral aspect of the hip bone, and you might remember it is formed by the fusion of the ilium, ischium, and pubis.
The acetabulum is surrounded on the outside by a margin that’s incomplete inferiorly, where the acetabular notch is situated; this makes it look like a bowl with a broken rim.
On the outside of the acetabulum margin, there’s the acetabular labrum, where labrum is a fancy word for lip, which continues over the acetabular notch with the transverse acetabular ligament.
The labrum increases the surface area of the acetabulum to allow more than half of the femoral head to fit within the acetabulum for stability.
There’s also a rough depression in the floor of the acetabulum - the acetabular fossa, right above the notch. These two structures, the acetabular notch and fossa, are surrounded by the thick and smooth lunate surface, the articular surface on which the head of the femur slides.Just like most joints, the hip joint is enclosed within a strong joint capsule formed by an external fibrous layer, called the fibrous capsule, and an internal layer, called the synovial membrane.

Joint capsule1:54–2:50

The fibrous layer attaches proximally to the acetabulum peripheral to the acetabular margin, as well as to the transverse acetabular ligament.
Distally, it attaches to the femoral neck, anteriorly at the intertrochanteric line and root of the greater trochanter; and, posteriorly, the fibrous layer heads towards but doesn't attach to the intertrochanteric crest.
Instead, most of its fibers take a spiral course and attach to the intertrochanteric line of the femur, whereas some deep fibers pass circularly around the neck, forming the orbicular zone which may play a role in stability.
The fibrous layer is actually thicker in some places, where it forms the three intrinsic ligaments of the hip joint which pass in a spiral from the pelvis to the femur, a bit like curled pasta made of fibrous tissue.

Ligaments2:50–5:40

Anteriorly and superiorly is the strong, Y-shaped iliofemoral ligament, which attaches to the anterior inferior iliac spine and the acetabular rim proximally, and the intertrochanteric line distally.
Considered the body’s strongest ligament, the iliofemoral ligament tightens and brings the femoral head tightly into the acetabulum when standing upright, and this prevents hyperextension of the hip joint.
Anteriorly and inferiorly, there’s the pubofemoral ligament, which arises from the obturator crest of the pubic bone and passes laterally and inferiorly to merge with the fibrous layer of the joint capsule and blends with the medial part of the iliofemoral ligament.
The pubofemoral ligament tightens during extension and abduction of the hip joint, preventing over-abduction. And finally, posteriorly there’s the ischiofemoral ligament which goes from the acetabular margin to the neck of the femur.
This ligament spirals superolaterally to the femoral neck, medial to the base of the greater trochanter and it limits internal rotation of the hip.
The synovial layer, the other component of the joint capsule, lines the internal surfaces of the fibrous layer, as well as any intracapsular bony surface not lined with articular cartilage.More specifically, it covers the neck of the femur between the attachment of the fibrous capsule and the edge of the articular cartilage of the head, as well as the nonarticular area of the acetabulum.
Speaking of which, the synovial membrane covering the femoral neck presents longitudinal synovial folds through which course the subsynovial retinacular arteries, which branch brom the medial and lateral circumflex femoral arteries, that supply the femoral head and neck.The synovial layer also gives off the ligament of the head of the femur, also called the ligamentum teres, which houses the artery to the head of the femur, a branch of the obturator artery.
The ligament of the head of the femur attaches to the margins of the acetabular notch along with the transverse acetabular ligament, and to the fovea on the femoral headThe ligament lies within the acetabular fossa, cushioned by a fat pad that fills the part of the fossa not occupied by the ligament of the head of the femur.
Quite cozy!Ok, now that we know our hip joint players, let’s look at the hip joint movements, and identify the main muscles that produce themFor example, flexion is produced by the iliopsoas, sartorius, rectus femoris, and pectineus.

Movements5:40–7:05

Extension is produced by gluteus maximus and the hamstrings, and it’s limited by the tightening of the iliofemoral ligament.
Abduction is carried out by gluteus minimus and medius, tensor fascia lata, and sartorius, adduction is a job for the adductor longus, brevis, and magnus and for the pectineus and gracilis muscles; medial rotation is achieved with a little help from gluteus minimus and medius and the tensor fascia lata; and finally, lateral rotation is partly produced by the short lateral rotator group - piriformis, obturator externus, obturator internus and associated gemelli, and quadratus femoris - but primarily by the gluteus maximus.
The hip joint is also capable of circumduction - which is a combination of all of the movements mentioned earlier. Now, all these movements wouldn’t be possible without arteries nourishing the hip joint, of course!

Vascular supply7:05–9:38

The large arteries in this area are the medial and lateral circumflex femoral arteries. The medial circumflex femoral artery is a branch of the profunda femoris artery.
It passes posteriorly and gives off the transverse and ascending branches. The transverse branch takes part in the formation of cruciate anastomosis which is situated at the upper part of the back of the femur at the level of the lesser trochanter, whereas the ascending branch passes to the trochanteric fossa, where it takes part in the formation of the trochanteric anastomosis.
It also gives off posterior retinacular branches, which supply the head and neck of the femur. The lateral circumflex femoral artery is the largest branch of the profunda femoris artery.
It runs laterally and divides into ascending, transverse, and descending branches. The ascending branch contributes to the trochanteric anastomosis and the transverse branch wraps around the femur posteriorly to take part in the cruciate anastomosis.
The descending branch runs down along the anterior border of the vastus lateralis, which it supplies and perforates to anastomose with a branch of the popliteal artery.
The trochanteric anastomosis is also joined by branches from the inferior gluteal artery and superior gluteal artery, while the cruciate anastomosis is also joined by a branch from the first perforating artery and by a branch of the inferior gluteal artery.
Now let’s look at the retinacular arteries in more detail. Generally speaking, these arteries run along the neck of the femur and through the retinaculum of the capsule, hence their name.
Retinacular arteries arising from the medial circumflex femoral artery are more numerous and supply most of the head and neck of the femur because they are able to pass beneath the unattached posterior border of the joint capsule.
Retinacular arteries arising from the lateral circumflex femoral penetrate the thick iliofemoral ligament, there’s fewer of them, and they are smaller.And one last important blood supply is the artery to the head of the femur, which is a branch of the obturator artery, it varies in size, and it traverses the ligament of the head of the femur.
When it comes to nerve supply, the hip abides by the Hilton’s law, which states that the nerves supplying the muscles crossing a joint also innervate that said joint, usually through direct articular branches.

Innervation9:38–10:24

So if you know the muscles that cross a specific joint, and the nerves that supply those muscles, you can deduce the nerve supply of he joint.
For example, the hip joint is crossed anteriorly by the flexors of the hip, which are innervated by the femoral nerve, so the anterior aspect of the hip joint is innervated by the femoral nerve.
The rest of the hip joint is innervated by the sciatic, obturator, and superior gluteal nerve. That is what we call information overload!

Quiz10:24–10:42

Because we don’t want you to strain any brain muscle, let’s take a break and see if you can identify some of the most important elements of the hip joint!All right, as a quick recap… the hip joint is a ball and socket type of synovial joint which is enclosed within a joint capsule formed by a fibrous and a synovial layer.

Review10:42–11:25

The fibrous layer of the joint capsule gives off three intrinsic ligaments of the hip joint: the iliofemoral ligament, the pubofemoral ligament, and the ischiofemoral ligament.
The synovial layer gives off the ligament of the head of the femur, which conducts the artery to the head of the femur. Hip joint movements include flexion, extension, adduction, abduction, internal and external rotation.