Hip Region II PDF

Musculoskeletal System Hip Region and Thigh II We will now consider the gluteal region at the back of the hip joint, and also discuss the muscles of the thigh.  Learning Outcomes After this lecture you should be able to: ▪ Identify the relevant bony...

Musculoskeletal System Hip Region and Thigh II We will now consider the gluteal region at the back of the hip joint, and also discuss the muscles of the thigh.  Learning Outcomes After this lecture you should be able to: ▪ Identify the relevant bony anatomy of the gluteal region and thigh ▪ Describe the muscles of the gluteal region and know their innervations and actions ▪ Know the course of the nerves and blood vessels in the gluteal region and thigh ▪ Give an account of the muscles of the thigh and know their innervations and actions ▪ Give the boundaries of the femoral triangle and popliteal fossa and list their content Here are the learning outcomes for this lecture.  Musculoskeletal System Hip Region and Thigh II Part 1: Gluteal Muscles This lecture is divided into 4 parts, and in this part we will focus on the muscles of the gluteal region.  Learning Outcomes After this lecture you should be able to: ▪ Identify the relevant bony anatomy of the gluteal region and thigh ▪ Describe the muscles of the gluteal region and know their innervations and actions ▪ Know the course of the nerves and blood vessels in the gluteal region and thigh ▪ Give an account of the muscles of the thigh and know their innervations and actions ▪ Give the boundaries of the femoral triangle and popliteal fossa and list their content The learning outcomes for this part of the lecture are that afterwards you should be able to Identify the relevant bony anatomy of the gluteal region and thigh Describe the muscles of the gluteal region and know their innervations and actions We’ll deal with the other outcomes later.  Boundaries of the Gluteal Region The glueal region or buttocks are located behind the hip joint, but extends around the joint anteriorly as well as far as the anterior superior iliac spine. The superior boundary is the iliac crest on both sides from the posterior superior iliac spine to the ASIS in front. It also include the top of the sacrum and some prefer to include the 5th lumbar vertebrae, but there is no consensus on that. It is easy enough to draw a plane across the superior aspect of the ilium which transects the spine of the L4 vertebra. This is the supracristal plane. Hence L5 is then included in the region, although it matters not. The lower border is defined by the pair of gluteal folds, which is where the deep fascia of the gluteal region merges with the deep fascia of the thigh. Both are called the fascia lata. There is a misconception that the gluteal fold is caused by the lower border of the large gluteal muscle, the gluteus maximus. However this in not so, as you can see from the overlay. The fibres of gluteus maximus cross the gluteal fold as they run inferolaterally to attach to the gluteal tuberosity of the femur. The intergluteal or natal cleft separates the gluteal region in right and left buttocks. The skin is thick and relatively insensitive and the superficial fascia is loaded with fat. This gives protection when we sit.  The Sciatic Foraminae Entry of nerves and vessels to this region is via the greater sciatic foramen, a space which also permits the entry of the piriformis muscle. This muscle is attached proximally to the anterior surface of the sacrum. The lesser sciatic foramen also permits the passage of a muscle, the obturator internus. This foramen also acts as a route for the pudendal nerve and internal pudendal vessels destined for the perineum. This neurovascular bundle wraps around the ischial spine, which acts as a boundary between the two foraminae.  External Lamina of the Hip Bone medius minimus axis of flexion/extension The external surface of the iliac bone presents three lines (gluteal lines) which demarcate the attachments of the gluteal muscles. These three lines are the posterior gluteal, anterior gluteal (which curves upwards towards the iliac tubercle and inferior gluteal lines respectively. The latter is the least well-defined. Gluteus maximus is attached behind the posterior gluteal line. Between the posterior and anterior lines is an area for the attachment of gluteus medius, and between the anterior and inferior lines is where gluteus minimus attaches. In the upright anatomical position, the axis of flexion and extension pass behind the hip. Hence, the anterior parts of gluteus medius and minimus are anterior to this line and hence can aid flexion, and also participate in medial rotation of the femur, whilst the posterior parts of these muscles (and gluteus maximus) are behind this line, and hence can aid extension and lateral rotation movements.  Hip Extensors Extension of the hip is primarily performed by gluteus maximus, and the hamstring muscles at the back of the thigh. Gluteus maximus is the bulkiest muscle in the body. It arises behind the posterior gluteal line of the ilium, the sacrum, and the sacrotuberous ligament. It has superficial and deep parts. Its deep part inserts onto the gluteal tuberosity on the upper shaft of the femur. The pull is an oblique one across the back of the hip joint, causing not only extension of the hip but also lateral rotation. The larger superficial part, inserts onto the iliotibial tract. We can see that on the image shown on the left. Being a large muscle, it has a large blood supply from both gluteal arteries. Its nerve supply however, is only from the inferior gluteal nerve. Still, that nerve arises from L5, S1 and S2, so THREE spinal segments isn’t too bad for a single muscle! We extend our hips during walking. I don’t know if you have ever felt the desire to feel your buttocks while walking (no? Me neither!), but if you did you will have noticed that gluteus maximus doesn’t actually contract at all during walking. That is the role of the hamstrings. Gluteus maximus though really comes into its own during strenuous extension against gravity, for example when standing up from a seated position, or climbing up stairs. With regard to the hamstrings, we shall discuss them later in part 3 of this lecture.  Iliotibial Band Gluteus maximus is essentially therefore an anti-gravity muscle, and gives power to extension of the hip when such power is needed. As well as extending the hip, it is also able to help in extension of the knee, via its action on the iliotibial band (tract). Most of its muscle fibres are inserted into this. The iliotibial band inserts distally on the lateral side of the tibia, just anterior to the axis of flexion/extension of the joint. It therefore causes extension of the knee when it is stretched. A similar effect can be achieved by leaning to the opposite side – this is why to rest muscular tone, we often lean whilst standing (waiting for a bus/train etc.). This action of tightening the iliotibial band is aided by a muscle called “tensor fasciae latae”, which arises from the anterior superior iliac spine and anterior part of the iliac crest and attaches to the anterior aspect of the iliotibial tract. Whilst gluteus maximus is supplied by the inferior gluteal nerve, the tensor fasciae latae is supplied by the superior gluteal nerve. Excessive strain on the iliotibial band can lead to pain on the lateral aspect of the knee. The extension of the knee provided by these two muscles (gluteus maximus and tensor fasciae latae), is secondary to the powerful contractions of the quadriceps muscles of the anterior thigh. We’ll discuss those muscles in due course.  Hip Abductors Posterior View of Hip Joint Lateral View of Hip Joint The abductors of the hip are gluteus medius and minimus. As we can see, these muscles arise from the lateral surface of the ilium between the gluteal lines. Both insert onto the greater trochanter, and they can both therefore pull the greater trochanter upwards causing abduction. Both of these muscles are innervated by the superior gluteal nerve. Abduction of the hip is a peculiar idea. How often do you see people walking down the road kicking their limbs outwards to the side? And yet, despite this being a nearly useless movement, we have these two powerful muscles for this action. In fact both of these muscles are required to work extremely hard during walking. If it were not for the action of these muscles, we would find it hard not to fall over when the opposite limb is lifted off the ground. Gravity would cause the body to fall to the side where there is no longer a foot on the ground, unless of course we shifted our centre of gravity to compensate.  Waddling Gait So patients with paralysis of the gluteus medius and minimus muscles shift their body weight so that their weight is balanced over the limb on the ground, but then needs to shift to other limb and so on. The result is a waddling gait.  Trendelenburg’s Sign The muscles are required to prevent the pelvis sagging on the opposite side. When these muscles are paralysed, the pelvis tilts, and there is said to be a positive Trendelenburg sign. Just to remind you once again, the nerve supply to these muscles is the superior gluteal nerve, whose roots are from L4-S1 of the spinal cord. The lower lumbar nerves are the most commonly injured spinal nerves. Long-term injuries lead to wasting of the muscles, with a flattening or hollowing out of the buttocks. This is evident on this patient here.  Lateral Rotators Beneath the large gluteal muscles lie the small lateral rotators. There are 5 of these muscles in all here. From superior to inferior these are the piriformis, superior gemellus, obturator internus, inferior gemellus and finally the quadratus femoris. All but the latter muscle insert into the trochanteric fossa, and they all have the same function. What’s more, all but the gemelli muscles have their own named nerve; i.e. the nerve to piriformis, nerve to quadratus femoris etc. But none of the detail of these muscles is worth remembering. Neither of them is critical to functioning of the hip, and in any case lateral rotation is not a key action at this joint. Just for completeness though, we give a brief account of each. The piriformis arises from the anterior surface of the sacrum and inserts into the trochanteric fossa. It emerges through the greater sciatic foramen, with the key nerves and vessels arranged around superior gluteals above and inferior gluteals below. In addition, the sciatic nerve usually enters the posterior thigh below it. The obturator internus arises from the obturator membrane, runs backwards, and then does a 90 degree turn to reach the trochanteric fossa. It is joined along the way by the gemelli muscles. The quadratus femoris arises from the ischial tuberosity and inserts onto the quadrate tubercle on the femur.  Musculoskeletal System Hip Region and Thigh II Part 2: Neurovasculature This is the 2nd part of the lecture on the hip region and thigh, where we will discuss the nerves and blood vessels of the region.  Learning Outcomes After this lecture you should be able to: ▪ Identify the relevant bony anatomy of the gluteal region and thigh ▪ Describe the muscles of the gluteal region and know their innervations and actions ▪ Know the course of the nerves and blood vessels in the gluteal region and thigh ▪ Give an account of the muscles of the thigh and know their innervations and actions ▪ Give the boundaries of the femoral triangle and popliteal fossa and list their content The learning outcome for this part of the lecture is that afterwards you should be able to Know the course of the nerves and blood vessels in the gluteal region and thigh We’ll deal with the other outcomes later.  Nerves of the Gluteal Region Superior gluteal nerve (L4-S1) Pudendal nerve (S2-S4) Inferior gluteal nerve (L5-S2) Perforating cutaneous Nerve (S2-S3) Sciatic nerve (L4-S3) Posterior cutaneous nerve of thigh (S2-S3) The gluteal region contains a lot of nerves! In addition to its numerous cutaneous nerves, the region contains four principal motor nerves for its own muscles, and three nerves just passing through. The motor nerves are the superior and inferior gluteal nerves, nerve to obturator internus and nerve to quadratus femoris. The three passing through are the tibial, common fibular and the pudendal. Of course the tibial and common fibular make up the sciatic nerve. In addition, there is a nerve to the piriformis muscle, but this supplies the muscle before it leaves the pelvis. The nerves are divided by the piriformis muscle. Above it lies the superior gluteal nerve. This arises from L4-S1 and supplies gluteus medius, minimus and tensor fasciae latae. Below it is the inferior gluteal nerve which arises from L5-S2 and supplies gluteus maximus. The sciatic nerve also emerges below piriformis, and this arises from L4-S3. Occasionally, the sciatic nerve may pass through the piriformis muscle (12.5%) or even above it (0.5%). The posterior cutaneous nerve of the thigh, together with the perforating cutaneous nerve of the thigh both arise from S2 and S3 of the spinal cord. Finally, the pudendal nerve is a nerve just passing through the gluteal region but doesn’t supply anything there. It is destined for the perineum, and crosses over the ischial spine to reach that. The nerves to obturator internus (L5-S2) and quadratus femoris (L4-S1) and are not shown here and indeed are not worthy of your attention. Piriformis itself is supplied directly by S1-2 roots but this is highly variable. Surface Anatomy of the Sciatic Nerve The sciatic nerve is the largest and most important nerve to be aware of. You should know the roots, course and distribution of this nerve and its branches. You should also know the surface anatomy of this nerve. It emerges into the greater sciatic foramen midway on a line drawn between the posterior superior iliac spine and the ischial tuberosity. From this point, the sciatic nerve arches (curves) to exit the gluteal region at a point midway between the ischial tuberosity and the greater trochanter.  Safe Area for Gluteal Injections One of the most common, yet preventable ways in which the sciatic nerve becomes injured, is via a misplaced gluteal injection. Knowing the surface markings of this nerve can prevent such injuries. The gluteal region can be divided into quadrants. The sciatic nerve lies then in the lower medial quadrant, hence intramuscular gluteal injections, should avoid this quadrant. Instead the upper lateral quadrant should be chosen.  Gluteal Injections If gluteal injections are to be made, the best strategy is to place the index finger onto the anterior superior iliac spine and the middle finger onto the iliac tubercle. The thumb should be anteriorly placed, so the left hand is used for a right-sided injection, and a right hand for a left- sided injection. The region between the index and middle fingers is the safe area in which injections should be placed – much further laterally than is commonly believed. The idea is to inject gluteus minimus or medius, not gluteus maximus. Injections into the sciatic nerve will leave the patient with pain (a burning, tingling sensation) radiating down the limb. There can be paralysis of the entire leg and foot. The most obvious symptom of this is drop-foot – the foot hangs limply at the ankle. There will also be paraesthesia over the leg and foot.  Arteries of the Gluteal Region Superior gluteal artery Internal pudendal artery Inferior gluteal artery The arterial supply to the gluteal region mirrors the gluteal nerve supply. The superior gluteal artery enters the gluteal region through a gap above the piriformis muscle. This gap is part of the greater sciatic foramen. The artery then divides into a deep branch, which courses between the gluteus medius and minimus muscles, and a superficial branch which lies external to gluteus medius. It can therefore contribute to the blood supply to the gluteus maximus muscle. The inferior gluteal artery also emerges through the greater sciatic foramen, but passes inferior to piriformis. Together, the gluteal arteries supply the gluteal muscles, tensor fasciae latae and the small rotator muscles. They also supply the surrounding bones, ligaments and joints. The internal pudendal artery is the artery of the perineum, and is merely passing through the gluteal region on route from the pelvis. All of the arteries of the gluteal region arise as branches of the internal iliac artery in the pelvis. The gluteal arteries have anastomoses with the arteries around the trochanters (trochanteric and cruciate anastomoses). These are important contributions to the blood supply to the hip joint.  Veins of the Gluteal Region Superior gluteal vein Internal pudendal vein Inferior gluteal vein The veins match the pattern shown in the arteries.  Vasculature of the Thigh Profunda Femoris Artery Anterior (Lateral) Circumflex Posterior Femoral (Medial) artery Circumflex 1st perforator 2nd perforator 3rdPopliteal perforator Artery 4th perforator The blood supply to the thigh comes almost entirely from a single vessel: the femoral artery. The femoral artery begins at the inguinal ligament, as a continuation of the external iliac artery. The surface landmark for the pulse of this artery is a finger-breadth below the mid- inguinal point. This is the mid-point between the ASIS and pubic symphysis. The artery courses through the anterior compartment giving muscular branches en route. It then heads towards the gap in the adductor magnus muscle, the adductor hiatus. Once it reaches the popliteal fossa at the other side of this hiatus, the artery becomes known as the popliteal artery. The femoral artery has only one major branch: the profunda femoris artery. This artery however has 6 branches. These are the medial and lateral circumflex femoral arteries and 4 perforator arteries. They perforate the intermuscular septae, to supply the muscles of the medial and posterior compartments of the thigh. The first perforator has ascending branches that anastomose with the arteries around the hip. This illustration shows the complexity of the anastomotic branches of these arteries. There is also a small contribution to the proximal part of the medial compartment from the obturator artery, but this is insignificant. As with all the deep arteries of the limb, the veins match the arterial pattern, hence you don’t need to learn these independently. Once you know the arteries, you already know the veins.  Musculoskeletal System Hip Region and Thigh II Part 3: Thigh Muscles and Movements We will now turn our attention to give an overview of the muscular compartments of the thigh. This is not a full account however, and you will need to do some additional reading around this subject.  Learning Outcomes After this lecture you should be able to: ▪ Identify the relevant bony anatomy of the gluteal region and thigh ▪ Describe the muscles of the gluteal region and know their innervations and actions ▪ Know the course of the nerves and blood vessels in the gluteal region and thigh ▪ Give an account of the muscles of the thigh and know their innervations and actions ▪ Give the boundaries of the femoral triangle and popliteal fossa and list their content The learning outcome for this part of the lecture is that afterwards you should be able to Give an account of the muscles of the thigh and know their innervations and actions We’ll deal with the remaining outcome in the final section next time.  Compartments of the Thigh The thigh contains three groups of muscles divided by fascial septae. These are the anterior, medial (or adductor) and posterior compartments. The anterior compartment contains the powerful anti- gravity extensor muscles of the knee and some flexors of the hip, whilst the medial compartment muscles perform the movement of adduction of the hip. One of those muscles also crosses the knee joint, but its action is minimal. Finally, there are the muscles of the posterior compartment, which are both flexors of the knee and extensors of the hip.  Intermuscular Septae of the Thigh The septae are termed the medial, lateral and posterior intermuscular septae as shown on the illustration.  Anterior Compartment of the Thigh The anterior compartment of the thigh contains some flexors of the hip, some flexors of the knee but more significantly a very powerful extensor of the knee. All of the muscles here are supplied by the femoral nerve and receive a blood supply from the femoral artery.  Quadriceps Femoris Rectus femoris Vastus intermedius Vastus lateralis Vastus medialis Quadriceps is the extensor of the knee. Its four parts are:- rectus femoris which arises from the A.I.I.S. (hence also flexes the hip), vastus lateralis arising from the lateral side of the linea aspera, vastus medialis arising from the medial side of the linea aspera, and vastus intermedius arising from the front of the femoral shaft. All four parts insert onto the tibial tuberosity.  Tendons of the Quadriceps Muscle Quadriceps tendon Patellar tendon The patella is a sesamoid bone in the common tendon. The part of the tendon proximal to the patella is known as the quadriceps tendon, whilst the distal part is referred to as the ligamentum patellae (or patellar ligament, or sometimes patellar tendon).  Quadriceps Femoris Attachments Vastus Vastus intermedius medialis Vastus Rectus lateralis femoris Patellar tendon Note how the vastus medialis is bigger and bulkier than the intermedius and lateralis. This is to do with corrective forces on the patella that we will discuss in the lecture on the knee joint. Both vastus medialis and lateralis contribute a band or retinaculum that help strengthen the front of the knee joint. Again, we’ll fill in the detail later. The distal attachment of the patellar tendon is onto the tibial tuberosity. This can be seen by the blue shading in this diagram on the left. The large area of red indicates the proximal attachment of the vastus intermedius, and just under the trochanters, there are small areas of red indicating the attachments of vastus medialis and lateralis. Mostly however, these two muscles arise more posteriorly close to the linea aspera. These are shown as the two thin red lines on the illustration on the right. The larger shading of red on that diagram is yet more attachment for the vastus intermedius.  Medial Compartment of the Thigh The medial compartment of the thigh contains the adductor muscles of the hip and is therefore also referred to as the adductor compartment. All of the muscles in this compartment are innervated by the obturator nerve and get a blood supply from the perforating branches of the profunda femoris. These muscles are important in walking when the limb is planted on the ground. In this position, these muscles pull the pelvis over the thigh for balance and stability. However, they are also used to pull the limbs together. This allows the knees and ankles to come into alignment for walking. Riders develop strong adductor muscles whilst gripping the saddle. Indeed, they are the most common group of individuals to suffer from strain of these muscles and it is therefore known as rider’s strain. Please Note: You need to know the attachments and actions of all of the muscles in this compartment (adductor longus, adductor brevis, adductor magnus, gracilis and obturator externus). You also need to know their nerve and blood supply.  The Thigh: Posterior Compartment ▪ Biceps Femoris » Long head » Short head ▪ Semimembranosus ▪ Semitendinosus ▪ Nerve supply » Tibial n. (except short head of biceps – Common fibular n.) ▪ Blood Supply » Profunda Femoris art. The muscles of the posterior compartment of the thigh are often referred to as the ‘hamstrings’. These muscles have a common tendinous attachment to the ischial tuberosity. This is utilised by the butcher who can tie his piece of ham with a piece of string wrapped around the tendons, ready to be hung on a hook in the butcher’s shop. They comprise the biceps femoris with its two heads – long head and short head. The semimembranosus and semitendinosus. The semitendinosus is located superficially, and it squashes the semimembranosus underneath. This flattens its tendon into a membrane. By definition, the hamstrings are the muscles of the posterior compartment of the thigh, which attach to the ischial tuberosity. All of the above do so. However, biceps has two heads. The short head of biceps femoris attaches to the lateral surface of the shaft of the femur. Hence it is not a hamstring. The hamstrings are joined by the deep part of a muscle from the medial compartment of the thigh: the adductor magnus. This portion of adductor magnus is referred to as the hamstring portion. All of the hamstrings are supplied by the tibial nerve, largely via L5-S1 fibres. The short head of biceps is supplied by the common fibular nerve, also taking L5 and S1 roots. Their blood supply is via the perforating arteries of the profunda femoris.  Compartments of the Thigh (not for inclusion in the lecture presentation) We have only mentioned a few specific muscles by name, and that is due to the time constraints placed up me here. Hence, you will need to read up on all of the muscles contained in these compartments. For each muscle you should know their attachments, innervations and actions. Please Note: This material is examinable as it is highly relevant to the anatomy of the lower limb. It is only omitted here as you will see these muscles in the dissecting room and there will be more time to discuss them there.  Muscles of the Thigh (not for inclusion in the lecture presentation) Medial Anterior Posterior First of all the muscles of the anterior compartment and muscles crossing the anterior aspect of the hip. The psoas major and iliacus are the most powerful flexors of the hip. We have at least mentioned the quadriceps femoris already, the most powerful extensors of the knee. Secondly the adductor group of muscles. We have mentioned adductor magnus in passing, but there’s lots more besides. And lastly, the posterior compartment muscles, most of which are hamstrings which we have discussed In the next few slides you will hear me make reference to a group of muscles called the pes anserinus group. This is formed by a single muscle from each of these compartments. Sartorius from the anterior compartment, gracilis from the medial compartment and semitendinosus from the posterior compartment. These all have a common insertion onto the medial aspect of the tibia. Please Note: This material is examinable as it is highly relevant to the anatomy of the lower limb. It is only omitted here as you will see these muscles in the dissecting room and there will be more time to discuss them there.  Movements of the Knee Joint (not for inclusion in the lecture presentation) HIP FLEXION KNEE EXTENSION Iliopsoas Red – rectus femoris Red – rectus femoris Blue – vasti muscles Green – sartorius HIP EXTENSION KNEE FLEXION Red – semimembranosus Red – semimembranosus Blue – semitendinosus Blue – semitendinosus Yellow - biceps femoris Yellow - biceps femoris Gluteus maximus Orange – gracilis Green – sartorius We have now given an account of all of the muscles of the thigh, and we have seen how they contribute to both movement of the hip and knee. The most important of the hip flexors is iliopsoas. The other muscles are weak. For extension, the three hamstrings are mostly used, but gluteus maximus is brought into play whenever powerful extension is required. For the knee, the forward movement is extension and this is the sole role of the quadriceps femoris. Flexion of the knee is brought about by the hamstrings and pes anserinus muscles. There are also some muscles in the calf which are important here, but we’ll discuss those later. Please Note: This material is examinable as it is highly relevant to the anatomy of the lower limb. It is only omitted here as you will see these muscles in the dissecting room and there will be more time to discuss them there.  Rotation of the Knee Joint (not for inclusion in the lecture presentation) MEDIAL ROTATION Red – semimembranosus Blue – semitendinosus Yellow – gracilis Orange – sartorius Green - popliteus LATERAL ROTATION Red – biceps femoris We had previously discussed rotation at the hip as those were principally the role of the gluteal muscles. The knee is only capable of rotation when flexed, and even then, the movement is slight. The medial rotators are the pes anserinus group and semimembranosus. There is an important lateral rotator called popliteus at the back of the knee and we’ll discuss that later. The single lateral rotator is the biceps femoris muscle. Please Note: This material is examinable as it is highly relevant to the anatomy of the lower limb. It is only omitted here as you will see these muscles in the dissecting room and there will be more time to discuss them there.  Musculoskeletal System Hip Region and Thigh II Part 4: Femoral Triangle and Popliteal Fossa In this final section of the lecture, we shall define two important spaces – the femoral triangle and the popliteal fossa.  Learning Outcomes After this lecture you should be able to: ▪ Identify the relevant bony anatomy of the gluteal region and thigh ▪ Describe the muscles of the gluteal region and know their innervations and actions ▪ Know the course of the nerves and blood vessels in the gluteal region and thigh ▪ Give an account of the muscles of the thigh and know their innervations and actions ▪ Give the boundaries of the femoral triangle and popliteal fossa and list their content The learning outcome for this part of the lecture is that afterwards you should be able to Give the boundaries of the femoral triangle and popliteal fossa and list their content  Walls of the Femoral Triangle The femoral triangle is a space contained between muscles of the anterior and medial compartments of the thigh, and is of importance because of its content: the femoral neurovascular bundle. The triangle is bounded superiorly by the inguinal ligament, laterally by the medial border of sartorius and medially by the medial border of adductor longus.  Adductor Canal There is a gap below the apex of the triangle between sartorius and adductor longus and this is the sub-sartorial or adductor canal. It also has the vastus medialis antero-laterally with a fascial membrane called the vasto-adductor membrane helping to separate these muscles and provide a covering for the vessels. This adductor canal allows the passage of the femoral artery and vein to reach the adductor hiatus. Here these vessels become continuous there with the popliteal artery and vein. Roof and Floor of the Femoral Triangle The roof of the triangle is the fascia lata and skin of the anterior thigh. The fascia is perforated by the saphenous opening, through which the superficial vessels (great saphenous vein & superficial inguinal lymph vessels) pass. The floor of the triangle is formed by three muscles. These are iliopsoas (iliacus part shown in green, psoas major part in yellow), pectineus (shown in red) and adductor longus (shown in blue).  Content of the Femoral Triangle The most lateral structure within the triangle is the femoral nerve, which sits on the psoas major muscle. Medial to that is a fascial sheath called the femoral sheath, and this contains the femoral artery, femoral vein and the deep lymphatics. The sheath only runs for about 4 cms distally, where the fascia blends with the connective tissues of the blood vessels. The femoral artery enters the triangle below the mid-inguinal point. On the medial side of the artery lies the femoral vein, which receives the great saphenous vein through the saphenous opening. This vein is often used clinically for access to the venous circulation. Medial to the vein lie the deep lymphatics, including the deep inguinal lymph nodes. These pass through a fat filled space called the femoral canal. The femoral canal is the site of a femoral hernia, where abdominal content may escape the confines of the abdomen. This affects about 3% of the populations and females are more likely to get one that males as their femoral canal is wider.  Boundaries of the Popliteal Fossa Semitendinosus Semimembranosus Biceps femoris Medial Lateral Plantaris Gastrocnemius (medial head) Gastrocnemius (lateral head) The popliteal fossa is a diamond-shaped area at the back of the knee. It is bounded medially by the medial hamstring muscles (semitendinosus and semimembranosus) above, and by the medial head of gastrocnemius below. The lateral boundaries are the biceps femoris above, and the lateral head of gastrocnemius and plantaris below. Roof and Floor of the Popliteal Fossa It has a roof formed by skin and the popliteal fascia. Piercing this fascia is short saphenous vein accompanied by the sural nerve, a branch of the tibial nerve. The floor formed by the distal surface of the femur, the back of the capsule of the knee joint, with its oblique popliteal ligament, and the popliteus muscle. We’ll discuss that muscle in the lecture on the knee joint. By the way, the tendon visible in this image on the right is the tendon of semimembranosus.  Content of the Popliteal Fossa Popliteal Vessels Common fibular Tibial nerve (peroneal) nerve The fossa contains the popliteal artery (deepest structure - but still palpable if you know where to press!), with the popliteal vein superficial to it. It also contains the tibial and common fibular (peroneal) nerves. These lie more superficial than the blood vessels.  Popliteal Lymph Nodes The space is full of fat embedded in which are lymph nodes. These lie deeply within the space alongside the popliteal artery. This is the only location other than the inguinal region where lymph nodes are found in the lower limb. On palpation of the popliteal fossa it is not uncommon to find swellings, but these may arise due to several factors. To palpate structures in the popliteal fossa, the popliteal fascia must first be relaxed by flexing the knee. Enlarged popliteal lymph nodes can also be felt as hard masses in this fossa. These may occur following infection in the foot or leg. Infections may travel through the superficial lymphatics that accompany the short saphenous vein, or they can travel via the deep lymphatics that accompany the deep arteries in the leg. Superficial lymphatics ultimately join the deep lymphatics by perforating the popliteal fascia.  Swellings in the Popliteal Fossa The popliteal fossa may house a swelling (aneurysm) of the popliteal artery. Such swellings are potentially life-threatening if there is a sudden rupture, as there may be a fatal haemorrhage. These swelling are easy to diagnose because the popliteal swelling will be pulsatile. Aneurysms are also common above the adductor hiatus (femoral aneurisms, as shown in the angiograph far left). Popliteal aneurysms are very common. The popliteal fossa also houses the popliteal vein, and this may have a thrombus which can be palpable. Dislodging a thrombus from this location can be fatal if it ends up blocking the pulmonary circulation. More unusually, there may be a neurofibroma (a nerve sheath tumour), or a lipoma (a tumour of the fat cells within the fossa.  Popliteal (Baker’s) Cyst Another cause of a swelling at the back of the knee is a popliteal cyst. This is caused by an expansion of a synovial bursa. Any swollen bursa in the popliteal region is termed a popliteal or Baker’s cyst, named after Dr William Baker who first described them. Baker’s cysts may occur following any knee inflammation, but most commonly are associated with an inflammatory reaction in the late stages of osteoarthritis of the knee.  Musculoskeletal System Hip Region and Thigh II And with that we conclude part 4 and indeed this whole lecture on the Hip Region and thigh. In the next lecture we shall turn our attention to the knee joint. It is one of the most complex joints in the entire body. I bet you can’t wait!