TLDR;
This video provides a detailed overview of the skeletal structure of the lower limbs, including the pelvic girdle, femur, tibia, fibula, patella, and the bones of the foot (tarsals, metatarsals, and phalanges). It describes the key features, articulations, and functions of each bone, as well as important landmarks and muscle attachment sites.
- The pelvic girdle connects the lower limb to the axial skeleton and consists of the hip bones and sacrum.
- The femur is the longest bone in the body and articulates with the hip bone, tibia, and patella.
- The tibia and fibula are the two bones of the leg, with the tibia bearing most of the weight.
- The foot is divided into the tarsus, metatarsus, and phalanges, which provide support and mobility.
Introduction to Lower Limb Bones [0:03]
The lower limb skeleton is divided into two functional components: the pelvic girdle and the bones of the free lower limb. The pelvic girdle connects the lower limb to the axial skeleton. It is a bony ring, also known as the pelvic ring, consisting of the right and left hip bones and the sacrum, which is common to both the pelvic girdle and the axial skeleton. Each hip bone consists of the ilium, ischium, and pubic bone and has three articulations: posterior medially with the sacrum at the sacroiliac joint, anteromedially with the other hip bone at the pubic symphysis, and with the head of the femur to form the hip joint.
Ilium Bone [1:20]
The ilium is the largest and most superior part of the hip bone, divided into a body and a wing (ala). The wing has lateral and medial surfaces, a crest, and anterior and posterior borders. The iliac crest, located superiorly, runs from the anterior superior iliac spine to the posterior superior iliac spine and has internal and external lips for muscle and deep fascia attachment. The lateral surface of the ala features the posterior, anterior, and inferior gluteal lines for gluteal muscle attachment. The medial surface is divided by the internal lip of the iliac crest into an anterior concave iliac fossa for the iliacus muscle and a posterior rough area with the auricular surface for the sacroiliac joint. The anterior border has the anterior superior iliac spine for the inguinal ligament and sartorius muscle attachment, and the anterior inferior iliac spine for the straight head of the rectus femoris muscle and iliofemoral ligament attachment. The posterior border includes the posterior superior iliac spine, for the oblique portion of the posterior sacroiliac ligaments and the multipidus muscle, and the posterior inferior iliac spine, below which is the greater sciatic notch. The ala continues inferiorly with the body of the ilium, joining the pubis and ischium to form the acetabulum.
Ischium Bone [3:28]
The ischium forms the posterior inferior part of the hip bone. Its posterior border forms the inferior margin of the greater sciatic notch, which transitions into the ischial spine, a triangular surface where the sacral spinous ligament and superior gemellus muscle originate. Below the spine is the lesser sciatic notch, separated from the greater sciatic notch by the sacral spinous ligament. Further down, the body of the ischium features the ischial tuberosity, a thick, rough prominence that supports weight while sitting and serves as an attachment site for the inferior gemellus muscle and the hamstrings. Anteriorly, the ramus of the ischium joins the inferior ramus of the pubis to form the ischiopubic ramus, which represents the inferior border of the obturator foramen.
Pubis Bone [4:33]
The pubis forms the anterior medial part of the hip bone. The body of the pubis has a symphysial surface on its medial side, which articulates with the contralateral pubis via the pubic symphysis, a cartilaginous joint. Anterosuperiorly, the body presents the pubic crest, where abdominal muscles attach, extending laterally as the pubic tubercle, the distal attachment point of the inguinal ligament. Superiorly and laterally, the body continues with its superior ramus, forming part of the acetabulum. The lateral part of the superior ramus has a sharp, raised edge called the pectineal line or pecten pubis, which joins the arcuate line of the ilium to form the iliopectineal line. Inferiorly and laterally, the pubis presents the inferior ramus, which joins the ramus of the ischium to form the ischiopubic ramus.
Acetabulum and Obturator Foramen [5:45]
The acetabulum is a large socket on the lateral face of the hip bone that articulates with the head of the femur to form the hip joint. The ischium provides the posterior inferior boundary, the ilium forms the upper boundary, and the pubis forms the rest near the midline. The margin of the acetabulum is incomplete inferiorly, forming the acetabular notch, and there is a rough depression in the floor called the acetabular fossa, both surrounded by the smooth lunate surface, the articular surface for the head of the femur. The obturator foramen is a large oval opening in the hip bone, bounded by the pubis, ischium, and their rami. It is normally closed by the obturator membrane, which has a small passageway, the obturator canal, for the obturator nerve and vessels. The foramen minimizes bone weight, while the membrane provides an extensive area for muscle attachment.
Femur Bone [7:40]
The femur, the longest bone in the body, is oblique and directed inferomedially. The head of the femur, a round prominence proximally, is situated superiorly and medially. The distal part, with two round prominences, is inferior and slightly more medial. The posterior part of the bone features a sharp longitudinal line, the linea 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 to form the knee joint. The femur transmits body weight from the hip bone to the tibia and provides attachment for 23 muscles. The proximal femur has a head, neck, and greater and lesser trochanters. The round head is covered in articular cartilage, except for the fovea capitis, where the ligament of the head of the femur attaches. The neck is trapezoidal, supporting the head and connecting to the shaft. The greater and lesser trochanters are large bumps at the junction between the femoral neck and shaft. The lesser trochanter is medial and inferior, for iliacus attachment, while the greater trochanter is lateral and superior, for abductor and rotator muscle attachment. The trochanteric fossa, a deep depression at the base of the greater trochanter, is where the tendons of the obturator externus, obturator internus, and superior and inferior gemellus muscles insert.
Femur Bone Shaft and Distal End [10:03]
The intertrochanteric line runs from the greater to lesser trochanter on the anterior side of the proximal femur, marking where the neck joins the shaft. The iliofemoral ligament attaches above this line, while the upper part of the vastus medialis attaches to the lower part. Posterior to the trochanters is the intertrochanteric crest, with the quadrate tubercle on its upper side, where the quadratus femoris muscle inserts. The femoral shaft is mostly smooth and rounded, providing origin for knee extensors, except for the linea aspera, a posterior longitudinal rough line for thigh adductor muscle attachment. The linea aspera, located around the middle third of the shaft, has medial and lateral lips and an intermediate ridge. Superiorly, the lateral lip blends with the gluteal tuberosity for gluteus maximus attachment, while the medial lip continues as a spiral line towards the lesser trochanter and then to the anterior surface, continuing with the intertrochanteric line. The intermediate ridge is the pectineal line, extending from the central part of the linea aspera to the base of the lesser trochanter. Inferiorly, the linea aspera divides into medial and lateral supracondylar lines, leading to the medial and lateral femoral condyles. The distal femur consists of the medial and lateral femoral condyles, which articulate with the menisci and tibial condyles to form the knee joint. The femoral shaft sits in about 9 degrees of valgus positioning, compensating for the oblique nature of the femur and allowing the femoral condyles to be on the same horizontal level when articulating with the tibia. The lateral surface of the lateral condyle has the lateral epicondyle, while the medial surface of the medial condyle has the medial epicondyle. The condyles are separated posteriorly and inferiorly by the intercondylar fossa but merge anteriorly, forming the patellar surface, which articulates with the patella. The epicondyles are where the medial and lateral collateral ligaments of the knee joint attach proximally. Superior to the medial epicondyle is the adductor tubercle, where part of the adductor magnus muscle inserts.
Patella Bone [13:34]
The patella, or kneecap, is a triangular bone located on top and in the middle of the femoral condyles. It has an anterior and a posterior surface, a superior base, an inferior apex, and two margins. The anterior surface is smooth and palpable on the anterior part of the knee. The posterior surface is covered with a thick layer of articular cartilage to 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 vastus muscles, helps keep the patella centered in the intercondylar groove during flexion and extension. The patella acts as the largest sesamoid bone in the body, providing leverage for the quadriceps during extension.
Tibia Bone [14:30]
The tibia, the second largest bone in the body, is located on the anterior medial side of the leg, nearly parallel to the fibula. The thicker, flat proximal end is superior, and the thinner, rounder distal end is inferior. The body of the tibia is somewhat triangular, with the tip of the triangle anterior and the base posterior. The tibia articulates with the condyles of the femur proximally and the talus distally, transmitting the body's weight to the foot and providing stability to the ankle joint. The tibia is divided into a proximal and distal end and a shaft. The proximal tibia resembles half a pyramid turned upside down, with a flat base called the tibial plateau. This plateau has medial and lateral articular surfaces that articulate with the condyles of the femur, separated by the intercondylar eminence, formed by two raised ridges of bone: the medial and lateral intercondylar tubercles. These are flanked by the anterior and posterior intercondylar areas. The intercondylar eminence fits into the intercondylar fossa between the femoral condyles and is where the menisci and principal ligaments of the knee attach. Underneath the base of the tibia are the tibial condyles. The lateral tibial condyle is on the anterior, lateral, and posterior side of the proximal tibia and has Gerdy's tubercle on its anterior surface, where the iliotibial tract attaches distally. The lateral condyle also presents a fibular articular facet for the head of the fibula on its posterior lateral surface. The medial condyle, situated on the anterior, medial, and posterior side of the proximal tibia, is where the semimembranosus muscle inserts.
Tibia Bone Shaft and Distal End [16:45]
The shaft of the tibia has three borders: anterior, medial, and lateral (interosseous), and three surfaces: medial, lateral, and posterior. The anterior border is the biggest and palpable under the skin. At its superior end is the tibial tuberosity, where the patellar ligament attaches distally. The lateral border, also known as the interosseous border, is where the interosseous membrane attaches to connect the tibia and fibula. The medial surface is subcutaneous, and together with the anterior border, they are known as the shin. The posterior surface is marked by the soleal line, where the popliteus muscle and fascia attach, and the tibialis posterior, flexor digitorum longus, and soleus muscles also originate. Distal to the soleal line is the nutrient foramen, an opening for the main artery supplying the proximal end of the bone and its marrow. The distal tibia is longer on the medial side, forming the medial malleolus. The inferior surface of the shaft and the lateral surface of the medial malleolus articulate with the talus, a bone of the foot. On the lateral side of the distal tibia, the sharp border of the interosseous border is replaced by the fibular notch, where the fibula attaches to form the tibiofibular joint.
Fibula Bone [18:23]
The slender fibula lies posterolateral to the tibia and articulates superiorly with the fibular facet on the lateral tibial condyle, forming the proximal tibiofibular joint. Inferiorly, it articulates with the fibular notch of the tibia to form the distal tibiofibular joint and with the talus to form the superior part of the ankle joint. The fibula has no weight-bearing function and serves mainly for muscle attachment. It is 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 called the apex and articulates with the fibular facet on the posterior lateral inferior surface of the tibial condyle. The shaft is twisted and provides many sites of muscular attachments. Similar to the shaft of the tibia, it is triangular, having three borders (anterior, interosseous, and posterior) and three surfaces (medial, posterior, and lateral). The distal end enlarges and extends laterally and inferiorly to form the lateral malleolus, which is more prominent and posterior than the medial malleolus on the tibia and extends approximately 1 cm more distally to form part of the ankle joint.
Tarsus Bones [20:07]
The foot is divided into three parts: the tarsus, metatarsus, and phalanges. The tarsus makes up the posterior part of the foot and consists of seven bones. The talus is the most superior bone of the foot and the only one that articulates with the leg bones superiorly at the ankle joint. Inferiorly, it articulates with the calcaneus to form the subtalar joint, and anteriorly, it articulates with the navicular at the talonavicular joint. It has a head that faces anteriorly, where it articulates with the navicular bone, a rough neck, and a body placed posteriorly. The superior surface of the body, or trochlea of the talus, is gripped medially and laterally by the two malleoli. The body of the talus narrows posteriorly and inferiorly, forming the posterior process of the talus, which has a groove for the tendon of flexor hallucis longus and is flanked by a prominent lateral tubercle and a less prominent medial tubercle. The calcaneus is the bone that makes up the heel and sits right underneath the talus. It articulates superiorly with the talus at the subtalar joint and anteriorly with the cuboid to form the calcaneocuboid joint. Its most important landmark is the fibular trochlea, an oblique ridge on its lateral surface that anchors a tendon for the everters of the foot. There is also a weight-bearing landmark on the posterior inferior part of the calcaneus called the calcaneal tuberosity, or heel, which has medial, lateral, and anterior tubercles. Projecting from the medial surface of the calcaneus is a shelf-like support for the head of the talus called the sustentaculum tali, which provides attachment for ligaments and muscles. The navicular is a flattened, boat-shaped bone that articulates anteriorly with the three cuneiforms and posteriorly with the head of the talus. Its medial surface projects inferiorly to form the navicular tuberosity, where most of the tendon of the tibialis posterior muscle attaches.
Cuboid, Cuneiform, Metatarsus and Phalanges Bones [22:42]
The cuboid is a cubicle bone and the most lateral bone in the distal row of the tarsus, having six surfaces that articulate with other bones of the foot. Its most important landmarks are the tuberosity of the cuboid and a groove on the inferior lateral surface for the fibularis longus (peroneus longus) muscle tendon. The last three bones of the tarsus are the wedge-shaped cuneiform bones. The medial cuneiform is the first and largest bone, the intermediate cuneiform is the smallest, and the lateral cuneiform is the only one to articulate with the cuboid. Each cuneiform articulates posteriorly with the navicular bone and anteriorly with the base of its corresponding metatarsal. The metatarsus comprises five metatarsal bones, all of which articulate with the tarsal bones proximally to form the tarsometatarsal joints. Distally, they articulate with the proximal phalanges, or the bones that make up the toes. They are numbered from the medial side of the foot, and each metatarsal has a large base proximally, a shaft, and a narrow head distally. The bases of the first and fifth metatarsals have large tuberosities for tendon attachment, and the tuberosity of the fifth metatarsal projects laterally over the cuboid. On the plantar surface of the head of the first metatarsal, there are two miniature bones, the medial and lateral sesamoid bones, embedded in the tendons passing along the plantar surface. Each toe, except for the first or great toe, has a proximal, middle, and distal phalanx, while the first toe has only a proximal and distal phalanx. Each phalanx has a proximal base, a shaft, and a distal head.
Summary [24:54]
The hip bones are formed by the fusion of the ilium, ischium, and pubis. The ilium is the superior part, the ischium forms the posterior inferior part, and the pubis forms the anterior medial part. The femur's proximal end consists of the femoral head and the greater and lesser trochanters, with the intertrochanteric line on the anterior side and the intertrochanteric crest posteriorly. The shaft of the femur features the linea aspera on its posterior side, while the distal femur consists of the medial and lateral femoral condyles. The tibia is located on the anterior medial side of the leg, with a proximal tibial plateau that has two articular surfaces divided by the intercondylar eminence and distal tibial condyles. The tibial shaft has a tibial tuberosity and the interosseous border for the interosseous membrane, inferior to which is the fibular notch. On the posterior tibia, there is a soleal line, and the distal tibia has the medial malleolus. The fibula lies posterolateral to the tibia, with a proximal 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 malleolus. The foot comprises the tarsus, metatarsus, and phalanges. The tarsus is made up of the talus superiorly, the calcaneus underneath the talus, the navicular in front of the talus, the cuboid, and the three cuneiform bones. The metatarsus has five metatarsal bones, and there are 14 phalanges that make up the bones in the toes. The first digit has two phalanges, while the other four digits have three phalanges each.
