Lower extremity anatomyWe might take the lower extremities for granted, but they are two well-oiled machines comprised of several complex anatomical parts working together in perfect harmony. Without them, you wouldn’t be able to walk to your favourite (or not so favourite) anatomy class, jump, run, stand, crouch, and so on. Therefore, try to keep them in top physical condition by giving them plenty of exercise.
The lower extremity can be divided into several parts or regions, as follows:
In this topic page, we will take a brief look at all of them and cover the basics of the entire lower limb.
Hip and pelvis
The structural framework of the hip region is provided by the pelvis, a structure composed of the pelvic girdle and the coccyx. In turn, the pelvic girdle consists of two hip bones and the sacrum, interconnected at the pubic symphysis and sacroiliac joints.
Each hip bone has three parts (ilium, ischium, pubis) and accepts the head of the femur to form the hip joint. This ball-and-socket joint is responsible for providing the lower extremity with an extensive degree of movement.
If you want to learn more about the hip joint and pelvic girdle, take a look below:
Several hip muscles act on the hip joint, causing the thigh, and hence the lower extremity, to move. They are divided into anterior and posterior muscle groups. The latter is further divided into superficial and deep subgroups. The anterior muscle group includes iliacus, psoas major and psoas minor. The posterior superficial muscles are the three gluteal muscles (gluteus maximus, gluteus medium, gluteus minimus), and the tensor fascia latae. In turn, the posterior deep muscles are the piriformis, obturator internus, obturator externus, superior gemellus, inferior gemellus, and quadratus femoris.
Let’s move now to the neurovasculature and see how the structures of the hip are nourished (you can learn more about the neurovasculature of the entire lower limb in this article). The main arteries of this region are the gluteal and femoral arteries, which stem from the iliac arteries. The venous drainage of the entire lower extremity is carried out by superficial and deep venous systems. The main veins draining the hip and pelvis are considered deep and include the external and internal iliac veins, which unite to form the common iliac veins. They have many tributaries, but the most important are the femoral veins, together with the deep veins of the pelvis and thigh. The main nerves supplying the hip region are the cluneal nerves, femoral cutaneous nerves, femoral nerve, obturator nerve, sciatic nerve, and gluteal nerves. All of them, except the cluneal nerves, originate from the lumbar and sacral plexuses.
If you want to find out more about the neurovasculature and take one step closer to mastering the hip and pelvis anatomy, check out the following resources.
Now that we’ve learned about the hip and pelvis, we’ll explore the thigh anatomy. The thigh is located between the hip and the knee. It is the strongest and most prominent part of the lower extremity, thus a personal favourite for fitness enthusiasts to showcase. The scaffold of the thigh is provided by the femur, the only bone of this region and the longest bone in the body. It has an upper extremity, a shaft, and a lower extremity, all of which are full of various structural landmarks. If you want to learn more details about the femur, take a look at the following video and article!
The femur participates in two major joints in the lower leg; the hip joint via its upper extremity, and the knee joint via its lower extremity. Several muscles attach to, and act on, the femur. They take full advantage of the mobility provided by two joints.
The muscles of the thigh can be divided into three groups: anterior, medial, and posterior. The anterior group occupies the anterior compartment situated at the front of the thigh, and includes the sartorius and quadriceps femoris. The latter is, in fact, one large muscle composed of four smaller ones called rectus femoris, vastus medialis, vastus lateralis, and vastus intermedius.
The medial group occupies, you guessed it, the medial compartment of the thigh. It includes the pectineus, adductor magnus, adductor minimus, adductor longus, adductor brevis, and gracilis. These muscles are also called the adductors of the thigh.
The posterior muscle group is the smallest group, occupying the posterior compartment of the thigh. It contains the three hamstring muscles called the semimembranosus, semitendinosus, and biceps femoris.
The muscles of the hip and thigh can be quite challenging to learn and success only comes with revision. If you want a summary of the muscles of both regions and a way to actively learn their attachments together with further details, study the following video and tackle the quiz!
The neurovasculature of the thigh is a direct continuation of the one from the hip. The arterial supply comes from the femoral artery and its branches. The main vein draining the thigh, and actually the entire lower limb, is the femoral vein. It is part of the deep venous system, drains into the external iliac vein, and is a direct continuation of the popliteal vein. The femoral vein also receives deoxygenated blood from the circumflex veins, the long saphenous vein, and the deep vein of the thigh. Innervation is provided by two major nerves and their branches: femoral and sciatic nerves. They originate from the lumbar and sacral plexuses, respectively.
Let’s now focus on the distal extremity of the femur because it takes part in a major joint of the lower extremity. The knee joint is formed by the close interaction of three bones: femur, tibia , and patella (kneecap). In fact, the entire joint consists of two articulations housed within one capsule, which is strengthened by various extracapsular and intracapsular ligaments.
You can find out more about the anatomy of the knee joint below!
The knee joint is a hinged joint capable of mainly flexion and extension, but also a small degree of rotation. These movements are performed with the help of several muscles of the thigh and leg. The knee extensors are the four muscles forming the quadriceps femoris, while the flexors include the biceps femoris, semitendinosus, semimembranosus, sartorius, popliteus, and gastrocnemius.
Like any structure in the human body, the knee also requires a neurovasculature supply. The arteries supplying it are the six genicular arteries which wrap around the knee. Together with other arteries of the lower extremity, they form the genicular anastomosis. They originate from the popliteal artery, the direct continuation of the femoral artery posterior to the knee. The main vein of the knee is the popliteal vein. It collects blood transported by all the veins of the leg and empties into the femoral vein. The main nerves supplying the knee joint are the genicular nerves, which stem from the tibial and common peroneal/fibular nerves, the main branches of the sciatic nerve of the thigh. In addition, the knee is also supplied by the articular branch of the obturator nerve and the muscular branches of the femoral nerve.
As you can see, knee anatomy is quite an intricate topic! If you want to learn more about the neurovasculature of the knee, take a look at the following resources.
Let’s move now forward with leg anatomy. In the realm of anatomy, the ‘leg’ is strictly the region between the knee and the ankle joints rather than the entire lower extremity, as erroneously referred to in common language. In this small section, we’ll briefly mention the main parts of the leg, namely the bones, muscles, and neurovasculature.
The two main bones of the leg are the tibia (‘shin bone’) located medially and the fibula, which is located more laterally. The tibia is the largest of the two, hence it is responsible for weight bearing. Two joints hold the tibia and fibula together (the superior and inferior tibiofibular joints), as well as an anatomical structure called the interosseous membrane.
Here are some further sources if you want to learn about all the nooks, cracks, and crannies of these two bones!
The leg is divided into three compartments: anterior, posterior, and lateral. The anterior muscle group includes: tibialis anterior, extensor hallucis longus, extensor digitorum longus, and fibularis/peroneus tertius.
The posterior compartment consists of seven muscles in total, divided into superficial and deep groups. The superficial muscles are the gastrocnemius, soleus, and plantaris (together forming the triceps surae), while the deep layer consists of the popliteus, tibialis posterior, flexor digitorum longus, and flexor hallucis longus.
The lateral compartment of the leg is the smallest one, containing only two muscles: fibularis/peroneal longus and brevis.
If you want to learn further details about these muscles and master the lower leg anatomy, take a look below!
The main arteries supplying the leg with oxygenated blood are the anterior and posterior tibial arteries together with their branches. The posterior tibial artery gives off a crucial branch called the fibular/peroneal artery which mainly supplies the muscles of the leg. The tibial arteries originate from the popliteal artery. When it comes to important veins of the leg; the small/short, and the great/long, saphenous veins provide the superficial drainage. The former opens into the femoral vein, while the latter into the popliteal vein. The deep veins of the leg are named fibular and tibial, with the tibial also finishing in the popliteal vein.
In terms of innervation, the leg receives it via the common fibular/peroneal, tibial, and saphenous nerves. The first two are branches of the sciatic nerve while the latter stems from the femoral nerve. These three nerves divide further to supply the various structures of the leg.
Ankle and foot
Last but not least, let’s tackle the ankle and foot anatomy. The ankle (talocrual) joint is a hinged joint capable of plantarflexion and dorsiflexion. It is composed of three bones: tibia, fibula, and talus (ankle bone). Out of the three, the fibula only plays a secondary and functional role, facilitating the movement of the ankle rather than structurally forming it. Providing the ankle with strength, but also flexibility, are ten ligaments in total, one of the most important being the deltoid ligament.
Sitting inferior to the talocrural joint is the subtalar (or talocalcaneal) joint, providing the foot with inversion and eversion capabilities. If you want to discover further information about the ankle joint, take a sneak peak below!
You’ve seen that a bone called the talus is involved in the ankle joint. However, this is only one out of many foot bones. These include the 7 tarsals; calcaneus, talus, navicular, cuboid, and cuneiform (three in total) bones, as well as the metatarsals, and phalanges. They are held together by several ligaments, the most well known being the collateral and long plantar ligaments of the foot.
Learning so many bones takes time, so firstly begin with their names. However, your anatomy exams will expect you to know the foot in detail and this is where the following resources come into play.
Several muscles attach to the previously named foot bones. They are divided into four groups: central, lateral, medial, and dorsal. The first three groups are collectively called the plantar muscles of the foot because they are located on the plantar aspect.
The central group of muscles is located within the central compartment of the foot. They are arranged into several layers. These muscles are called; flexor digitorum brevis, quadratus plantae, lumbricals, plantar interossei, and dorsal interossei.
Moving more laterally, but still on the plantar side of the foot, we meet the muscles of the lateral compartment: abductor digiti minimi, flexor digiti minimi brevis, and opponens digiti minimi.
The medial group of muscles are also three in number and they are called abductor hallucis, adductor hallucis, and flexor hallucis brevis.
Now let’s go to the dorsum, or top, of the foot. There are only two dorsal muscles here: extensor digitorum brevis and extensor hallucis brevis.
Although the vast majority of resources separate the foot muscles by compartments, they can also be separated according to their locations. The muscles originating further up from the leg are called the ‘extrinsic’ muscles of the foot, while those attaching strictly below the ankle are called the ‘intrinsic’ muscles.If you want to learn more about all of these muscles, take a look at the following videos!
The arterial supply of the foot is provided by the dorsal artery of the foot and its branches on the dorsal side. In turn, the deep plantar arch and its branches are responsible for the vascularisation of the plantar side. In terms of venous drainage, the superficial veins of the foot consist of the superficial dorsal and plantar venous networks. The deep veins include the deep plantar arch and the dorsal venous arch. These superficial and deep systems collect blood from the marginal, digital, and metatarsal veins of the foot. The superficial veins drain into the dorsal venous arch. In turn, the venous arches drain into the saphenous veins of the leg. Regarding innervation, the main nerves responsible for supplying the foot are the medial and plantar nerves, together with the digital nerves.
If you want to learn more about the neurovasculature of the foot as well as its origins, take a look at the following video!
In order to properly round up the study process of the lower extremity anatomy, we have designed a quiz that specially aims at the bones, joints, muscles, nerves and vessels of this region. Take this quiz and reinforce your knowledge about the lower limb anatomy!