Bones of the lower limb: Anatomy

0:03 The footbones connected to the leg bone. The leg bones connected to the thigh bone. All right, as a quick recap, just kidding. The lower limbs actually have an incredibly detail-rich skeleton that can be divided into two functional components. The pelvic girdle, which connects the lower limb to the axial skeleton, and the bones of the free lower limb. The pelvic girdle is a bony ring known as the pelvic ring consisting of the right and left hipbones and the sacrum which is common to both the pelvic girdle and the axial skeleton. Each hipbone consists of the illium, isium and pubic bone and has three articulations. Posterior medially it articulates with

0:49 the sacrum at the sacro iliac joint. Antromediately it articulates with the other hipbone at the pubic symphysis. And finally, it articulates with the head of the femur to form the hip joint. Enjoying our osmosis videos? Unlock your full potential with an Osmosis subscription. Get unlimited access to every Osmosis feature and resource with a free 7-day trial. Okay. So the illiam is the largest and most superior part of the hipbone and it can be divided into a body and a wing. The wing or alla of the illiam has a lateral and a medial surface, a crest

1:34 and two borders, anterior and posterior. Superiorly, there's the iliac crest which begins at the anterior superior iliac spine and it extends posteriorly to the posterior superior iliac spine. The crest has an internal and external lip and serves as an important attachment site for muscles and deep fascia. Next, the lateral surface of the alla has three rough arched lines called the posterior, anterior and inferior glutial lines where the glutial muscles attach. These are the muscles of your bottom. Next, the medial surface can be divided into two by the internal lip of the iliac crest. The anterior portion is concave and it forms the iliac fossa

2:21 which is where the iliacis muscle attaches. The posterior medial portion is rough and it presents the uricular surface which is shaped like an ear and articulates with an identical surface on the sacrum to form the sacro iliac joint. Next, the anterior border presents the anterior superior iliac spine superiorly where the inguinal ligament and the storius muscle attach. And underneath it there's the anterior inferior iliac spine where the straight head of the rectus feorous muscle and the ilophemeral ligament of the hip joint attach. Finally the posterior border has a posterior superior iliac spine which is where the oblique portion of the

3:06 posterior sacro iliac ligaments and the multipetus muscle attach. Underneath it there's a posterior inferior iliac spine below which is a deep notch the greater sciatic notch. Okay. So the a continues inferiorly with the body of the illium which joins the pubis and isium to form the acetabulum. Next let's look at the is it which forms the posterior inferior part of the hipbone. The posterior border of the ishium forms the inferior margin of the greater sciatic notch. At the end of the notch, there's a triangular surface called the isial spine where the sacral spinus ligament and the superior jamlis muscle originates. Below the spine, there's the lesser sciatic notch which is separated from

3:52 the greater sciatic notch by the sharp demarcation of the sacral spinus ligament. Going even further down, the body of the is it has an issial tuberosity which is a thick rough prominence that supports our weight while sitting and where the inferior jamalis muscle and the hamstrings attach. Unfortunately, these aren't actual hamstrings but rather a pair of three posterior thigh muscles. Anteriorly, the ramis of the ishium joins the inferior ramis of the pubis to form a bar of bone called the issio pubic ramis that represents the inferior border of the opterator foromin. Okay. Now finally there's a pubis which forms the anterior medial part of the

4:37 hipbone. The body of the pubis has a symphysial surface on its medial surface which articulates with an identical surface on the body of the contrlateral pubis via the pubic symphysis. The pubic symphysis is a cartilagynous joint that sits between and joins the pubic bones at the respective rami. An anterior superiorly the body presents a rounded thickening called the pubic crest which is where the abdominal muscles attach. The crest extends laterally as a pubic tubacle which is the distal attachment point of the inguinal ligament. Superior and laterally the body of the pubis continues with its superior ramis which forms part of the acetabulum. The lateral part of the superior ramis

5:23 also has a sharp raised edge. The pectinial line or pectin pubis which joins the arcuate line of the illium to form the ilopectinial line. Inferiorly and laterally the pubis presents the inferior ramis which joins the ramis of the ishium to form the issopubic ramis. Now that we know a bit about the bones separately, let's talk about what they form together. First there's the acetabulum which is a large socket of the lateral face of the hipbone that articulates with the head of the femur to form the hip joint. Each of the three primary bones contributes to the acetabulum as follows. The isium provides the posterior inferior boundary. The illium

6:09 forms the upper boundary and the rest near the midline is formed by the pubis. The margin of the acetabulum is incomplete inferiorly where the acetabular notch is situated and makes it look like a cup with a broken rim. There's also a rough depression in the floor of the acetabulum, the acetabular fossa right above the acetabular notch. These two structures, the acetabular notch and depression are surrounded by the thick and smooth lunate surface of the acetabulum. the articular surface on which the head of the femur slides. Moving on, there's a large oval opening of the hipbone called the opterator forin bounded by the pubis isium and the

6:54 rami. Normally the opterator forin is closed by the very strong opterator membrane which has a tiny passageway for the opterator nerve and vessels called the opterator canal. The purpose of this forman is to minimize bone weight while its closure by the opterator membrane provides an extensive area for the fleshy attachment of internal and external optator muscles. Okay, so that was enough info to make your hipbones crack. So why don't you pause for a minute and see if you can label the most important features of the hipbones before we move on. D.

7:40 Okay, great. Let's now move on to the bones of the free lower limb, which includes the femur, tibia, fibula, patella, and the bones of the feet. Now, the femur is the longest bone in the body and looks like the letter L turned upside down, making them oblique and directed inferior medially as a femur progresses distally. To place it in its anatomical position, the head of the femur, which is the part with a round prominence proximally, should be situated superiorly and medially. Its distal part, the bit with the two round prominences, is situated inferiorly and a bit more medial than the superior part because the femur has an oblique position in the body.

8:26 And finally, on the posterior part of the bone, there's a sharp longitudinal line, the linear aspera. The head of the femur articulates with the acetabulum to form the hip joint while the distal femur articulates with the tibia and patella known as the kneecap to form the knee joint. The femur's main purpose is to transmit body weight from the hipbone to the tibia when a person is standing and at the same time to provide attachment for 23 muscles. Okay. So the proximal femur has a head, neck and the greater and lesser troanters. The round head of the femur makes up about 2/3 of a sphere and is covered in articular cartilage except for a medially placed depression which creates

9:12 a pit called the phobia capus which is where the ligament of the head of the femur attaches. The neck of the bone is trapezoidal with its narrow end supporting the head and its broader base continuous with the shaft of the femur. Now at the junction between the femoral neck and shaft, there are two large bumps called trocanters. The lesser trocanter is situated medial and inferior to the junction and is where the ilio attaches. Lateral and superior to the junction is the much larger greater trocanter where the abductor and rotator muscles of the thigh attach. At the base of the greater trocanter, there's a deep depression called the trocanteric fossa, which is where the tendon of the opterator externus muscle,

9:58 opterator internis, and the superior inferior gllus all insert. Now, running from the greater to lesser troanter, there's also the intertrocanteric line on the anterior side of the proximal femur, which is where the neck of the femur and femoral shaft join. The ilophmeral ligament considered the strongest of the human body attaches above this line while the upper part of the vasis mediialis attaches to the lower part of the interrocanteric line. Posterior to the trocanters there's a similar but smoother and more prominent ridge the interrocanteric crest which in turn has a rounded elevation on its upper side called the quadrat tubrical and the quadratus feorous muscle inserts on both these elements.

10:49 Most of the femoral shaft is smoothly rounded and it provides fleshy origin to extensors of the knee. The exception is a posterior longitudinal rough line called the linear aspa which is where the ainurosis of the thigh adductor muscles attach. The linear aspa is situated around the middle third of the femoral shaft and it presents a medial and lateral lip and an intermediate ridge. Superiorly, the lateral lip blends with a broad rough patch of bone called the glutial tuberosity which is where part of the glutius maximus attaches. The medial lip on the other hand continues superiorly as a spiral line which extends towards the lesser troanter and then passes to the anterior surface of the femur where it continues

11:36 with the intertccantic line. The intermediate ridge is called the pectinal line and it extends from the central part of the linear aspera to the base of the lesser troanter. Switching to its inferior part here, the linear aspir divides into a medial and lateral supercondular lines, which lead you to, you've guessed it, the medial and lateral femoral condis. Speaking of which, let's look at the distal femur, which consists almost entirely of two round prominences called the medial and lateral femoral condiles. The femoral condiles articulate with the menisci which are two plates of cartilage on top of the tibia and with the tibial condiles to form the knee joint. The femoral shaft sits in about

12:22 9° of valgus positioning from the vertical plane which compensates for the oblique nature of the femur and allows the femoral condiles to be on the same horizontal level when articulating with the tibia. The lateral surface of the lateral condile has a central projection called a lateral epicondile. Whereas the medial surface of the medial condile has a medial epicondile. The condiles are separated posteriorly and inferiorly by the intercondular fossa but they merge anteriorly forming a shallow longitudinal depression called the patellar surface which articulates with the patella. The epicondiles are where the medial and lateral collateral ligaments of the knee joint attach proximally superior to the medial epicondile.

13:08 There's another elevation unsurprisingly called the adductor tubacle where part of the adductor magnus muscle inserts. Okay, so that was enough info to make you fall on your knees. Why don't you pause for a minute and see if you can label the most important features of the femur before we move on. Ready? Okay. So, the patella or kneecap is a triangular bone located on top and in the middle of the femoral condiles. It has an anterior and a posterior surface, a superior base, and an inferior apex and two margins. The anterior surface is smooth, and you can actually feel it on the anterior

13:54 part of your knee. The posterior surface is covered with a thick layer of articular cartilage so it can articulate with the patellar surface of the femur. This surface is divided by a vertical ridge into a narrower medial and wider lateral articular surface. The ridge along with the balanced pull of the vasis muscles helps keep the patella centered in the intercondular groove as it articulates with the femur during flexion and extension. The patella acts as the largest sesimoid bone in the body and functions to provide leverage for the quadriceps during extension. Now that was a breeze, wasn't it? Let's move on to the second largest bone of the body, the tibia, which is located on the anterior medial side of the leg

14:39 nearly parallel to the fibula. This bone kind of resembles a scepter. So the thicker and flat proximal end is superior and its thinner and rounder distal end is situated inferiorly. And because the body of the tibia is somewhat triangular, the tip of the triangle should be anterior while its base should be posterior. The tibia articulates with the condiles of the femur proximally and the tus distally. So it transmits the body's weight to the foot and it provides stability to the ankle joint. The tibia can be divided into a proximal and distal end and a shaft. Okay. So the proximal tibia resembles half a pyramid turned upside down. Superiorly, the base of the pyramid is

15:25 rather flat. So it's called the tibial plateau. This plateau has medial and lateral articular surfaces that articulate with the condiles of the femur. The articular surfaces are separated by an intercondular eminence formed by two raised ridges of bone. The medial and lateral intercondular tubacles which are flanked by the anterior intercondular area to the front and posterior intercondular area to the back. The intercondular eminence fits into the intercondular fossa between the femoral condiles and it's where the menisci and principal ligaments of the knee attach. Moving on, underneath the base of the tibia, there are two prominences called the tibial condis. The lateral tibial

16:11 condile is situated on the anterior, lateral and posterior side of the proximal tibia. On the anterior surface of the lateral tibial condile, there's Gert's tubacle which is where the ilotibial tract attaches distally. The lateral condile also presents a fibular articular facet for the head of the fibula on its posterior lateral surface. The medial condile situated on the anterior, medial and posterior side of the proximal tibia is where the semimebrinous muscle inserts. Moving on, the shaft of the tibia has three borders anterior, medial and lateral or interosius and three surfaces medial, lateral and posterior.

16:57 The anterior border of the tibia is the biggest and you can feel it under your skin throughout its length. At the superior end of the anterior border, there's a tibial tuberosity which is where the patellar ligament attaches distally. Next, the lateral border is also known as the interosius border and it's where the interosius membrane attaches to connect the tibia and fibula. The medial surface of the tibia is subcutaneous as well and together with the anterior border they're collectively known as a shin. The posterior surface is marked by a rigid bone known as the solial line which is where the poplatus muscle and fascia attach and tibialis posterior flexor digitorum longus and solius muscles also originate here. Distal to

17:44 the solial line, there's the nutrient foramin, an opening in the bone that gives passage to the main artery supplying the proximal end of the bone and its marrow. Finally, the distal tibia is longer on the medial side, a bit like a claw and it forms the medial malololis. The inferior surface of the shaft and the lateral surface of the medial malololis articulate with the talis, a bone of the foot. On the lateral side of the distal tibia, the sharp border of the interosius border is replaced by the fibular notch where the fibula attaches to form the tibopiibular joint. All right. Now the slender fibula lies posterior lateral to the tibia. The fibula articulates superiorly with the

18:31 fibular facet on the lateral tibial condile and together they form the proximal tibio joint. Inferiorly, it articulates with the fibular notch of the tibia to form the distal tibio joint. It also articulates with the talis to form the superior part of the ankle joint. The fibula has no function in weight bearing and it serves mainly for muscle attachment. It can be divided into a distal end, a proximal end and a shaft. The proximal end has an enlarged head with a small neck inferior to it. The head has a pointed peak on top of it called the apex and articulates with the fibular facet on the posterior lateral inferior surface of the tibial condile.

19:16 The shaft is twisted and provides many sites of muscular attachments. Similar to the shaft of the tibia, it's triangular having three borders anterior, interosius and posterior and three surfaces medial, posterior and lateral. The distal end enlarges and extends laterally and inferiorly to form the lateral malololis. The lateral malololis is more prominent and posterior than the medial malololis on the tibia. And it extends approximately 1 cm more distally to form part of the ankle joint and help you locate furniture in the dark. Ow. Absolutely fibulous. We're done with two more bones. Before we move on to the bones of the foot, take a rest and try and recognize the main parts of the

20:02 tibia and fibula. We've reached the foot. The foot can be divided into three parts. The tarsus, metatarsus, and fanges. First up, the tarsus makes up the posterior part of the foot, and it consists of seven bones. The talis is the most superior bone of the foot and the only one that articulates with the leg bone superiorly at the ankle joint. Inferiorly it articulates with the calccanous to form the subtailor joint and anteriorly it articulates with the nvicular at the tailonicular joint. Overall it has a head that faces anteriorly where it articulates with the nvicular bone and also has a rough neck and a body which is placed posteriorly.

20:50 The superior surface of the body or tricleia of the talis is gripped medially and laterally by the two maloli. Finally, the body of the talis narrows posteriorly and inferiorly and forms posterior process of the talis. The process has a groove for the tendon of flexoralis longus and is flanked by a prominent lateral tubal and a less prominent medial tubacle. Second up in the tarsus, the calccanous is the bone that makes up your heel and it sits right underneath the talis. The calccanous articulates superiorly with the talis of the subtailor joint and anteriorly with the cuboid to form

21:35 the calccanio cuboid joint. Its most important landmark is a fibular troleia, an oblique ridge on its lateral surface which anchors a tendon for the averters of the foot, the muscles which move the sole of the foot outward. There's also a weightbearing landmark on the posterior inferior part of the calccanous called the calccanial tuberosity casually called the heel which is a medial, lateral and anterior tubacles. And finally projecting from the medial surface of the calccanous there's a shelfike support for the head of the talis called the sustentaculum ti which provides attachment not for books but for ligaments and muscles. Third the nvicular is a flattened boatshaped bone which articulates

22:21 interiorly with the three uniforms and posteriorly with the head of the talis. Something to know is that its medial surface projects inferiorly to form the nvicular tuberosity which is where most of the tendon of the tibialis posterior muscle attaches. Fourth, the cuboid is a cubicle bone as expected and it's the most lateral bone in the distal row of the tarsus. This means it has six surfaces anterior, posterior, dorsal, planter, medial and lateral, most of which articulate with other bones of the foot. Its most important landmarks are the tuberosity of the cuboid. And on the inferior

23:06 lateral surface, there's a groove for the fibularis longus, a peronous longus muscle tendon. The last three bones of the tarsus are the wedge-shaped kuniform bones. The medial ununiform is the first and largest bone. The intermediate kuniform is the smallest of the bunch. And the third and final bone is a lateral kuniform which is the only one to articulate with the cuboid. Each kuniform articulates posteriorly with a nvicular bone and anteriorly with a base of its corresponding metatarsal. So let's look at the metatarsus now which comprises of five metatarsal bones all of which articulate with the tarsel bones approximately to form the toarsome metatarsal joints. Distally they

23:53 articulate with the proximal felanges or the bones that make up the toes. They're numbered from the medial side of the foot and each metatarsal has a large base proximately a shaft and a narrow head distally. Some rather fun facts about them include the fact that the bases of the first and fifth metatarscils have large tuberosities for tendon attachment and that the tuberosity of the fifth metatarsal projects laterally over the cuboid. And finally on the planter surface of the head of the first metatarsil there are two miniature bones the medial and lateral sesimoid bones and they're embedded in the tendons passing along the planter surface. And finally, we've reached the 14 fanges. Each toe except for the first or

24:39 great toe has a proximal, middle, and distal fangi, while the first toe has only a proximal and distal fangi. And each failank has a proximal base, a shaft, and a distal head. Phew. All right, as a quick recap, the hipbones are formed by the fusion of three primary bones, the illium, isium, and pubis. The ilium is the superior part of the bone. The is it forms the posterior inferior part of the hipbone. The pubis forms the anterior medial part of the hipbone. The femur's proximal end consists of the femoral head and the greater and lesser troanters. There's also the intertrocanteric line on the anterior side of the proximal

25:25 femur and conversely posterior to the troanters the intertrocanteric crest. The shaft of the femur features the linear aspera on its posterior side while the dist femur consists almost entirely of the medial and lateral femoral condiles. The tibia is located on the anterior medial side of the leg. The proximal tibia comes with a tibial plateau which has two articular surfaces divided by the intercondular eminence and distal to the plateau are the tibial condiles. The tibial shaft has a tibial tuberosity and the interosius border for the interosius membrane inferior to which we can find the fibular notch. On the

26:10 posterior tibia there's a solial line and the distal tibia has a claw medially the medial malololis. The fibula lies posterior lateral to the tibia. Its proximal end has a large head superior to a small neck and a pointed peak where the articular surface for the fibular facet lies. The distal end of the fibula extends laterally and inferiorly to form the lateral malololis. Finally, the foot comprises of the tarsus, metatarsus and fanges. The tarsus is made up of the talis superiorly, the calccanous right underneath the talis and the nvicular which sits directly in front of the calccanous. The cuboid which also sits

26:57 in front of the talis and the three uniform bones. The metatarsus has five metatarsal bones. And finally there are 14 fanges that make up the bones in the toes. The first digit or great toe has two fanges proximal and distal. The other four digits have three fanges each proximal, middle and distal, respectively. Helping current and future clinicians focus, learn, retain, and thrive. Learn more.