Bones of the Legs

BiologyHuman biology

Three Main Bones of the Leg

Starting from the hip to the ankle, three bones which form the leg are as −

  • Femur

  • Tibia

  • Fibula.

Femur − Femur is the single, thick bone that runs from the hip joint to the knee joint. It’s the strongest bone of the leg accounting for one-quarter of the total height of a person.

Tibia − Tibia runs along the lower leg, and is called the shin bone. Along with the fibula, it runs from the knee joint to the ankle. It is stronger and thicker than fibula.

Fibula − Fibula along with the tibia, the fibula joins the knee and ankle. It is thinner than the tibia forming the lateral part of the ankle. It is also called the calf bone.

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Hip Joint and Its Movements

The hip joint is a ball and socket joint that comprises the head of the femur and the acetabulum of the pelvis. The point where the upper end of the thigh bone, the femur, meets the pelvis is referred to as the acetabulum. These two bones act as a ball and a cup fitted together enabling the femur to rotate freely.

The head of the femur, the rounded proximal end attaching to the acetabulum, acts as the centre of the entire axis.

The hip joint enables movement in three major axes each of which is perpendicular to one another.

  • Movements of flexion and extension are enabled by the transverse axis.

  • The internal and external rotation along the thigh is enabled by the longitudinal axis.

  • Abduction or adduction, also referred to as the forward and backward movements are allowed by the sagittal axis.

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Load transmission, enhancing hip joint stability by maintaining negative pressure and regulating synovial fluid’s hydrodynamic properties are some of the functions of the hip joint.

Unlike the shoulder joint, the hip joint is a substantial contributor to joint stability bearing the stress of one’s body weight.

Ligaments of the Hip Joint

Ligaments of the hip are mainly classified into −

  • Intracapsular

  • Extracapsular.

The ligament of the head of the femur is the only intracapsular ligament, a small structure that also acts as a minor arterial supply to the hip joint.

The extracapsular ligaments are a group of three ligaments on the outer surface of the hip joint. They are as listed below.

Iliofemoral ligament − Being the strongest of the three, it prevents hyperextension of the hip joint.

Pubofemoral ligament − this triangular-shaped ligament reinforces the capsule anteriorly and inferiorly.

Ischiofemoral ligament − having a spiral orientation, it reinforces the capsule posteriorly preventing hyperextension and holding the femoral head in the acetabulum.

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Knee Joint

The knee joint is a complex structure of two joints combined to form one single joint capsule. The femur, the tibia and the patella together form the knee joint.

The tibia and fibula combine to form the tibiofibular joint which forms the medial and lateral connections.

Mostly, joints are formed by the connection of two different bones. As an exception, some bones don’t connect with other bones, instead, they are connected directly to tendons or are embedded within the muscle. Such bone is called sesamoid bone. The patella (knee cap) is the largest sesamoid bone in the body. The patella and femur together form the patellofemoral joint.

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The knee joint should be strong enough to bear body weight and at the same time, be flexible for movements of the body. Hence, this joint is surrounded by several fat pads and bursae. Commonly found near joints, the bursa is a fluid-filled sac that reduces friction between two bones and acts as lubricating structures between tendons and bones. The knee joint has three bursae - suprapatellar, prepatellar, and infrapatellar.

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Knee Ligaments

Ligaments play a key role in keeping the bones in place. There are four main ligaments in the knee joint as follows −

  • The medial collateral ligament (MCL) forms the inner portion of the knee providing medial stability. The lateral collateral ligament (LCL) forms the outer portion of the knee providing lateral stability to the knee.

  • The anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL) present on the inner side of the knee provide anterior, posterior and rotatory stability of the knee.

  • Crescent-shaped, thick cartilage called the medial meniscus and the lateral meniscus attach to the tibia giving stability to the knee and acting as shock absorbers. The medial meniscus forms the inner part of the knee joint while the lateral meniscus forms the outer part.

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Lower Leg Muscles

Several muscles in the lower leg work together to move the feet and ankle.

Gastrocnemius − One of the main muscles in the lower leg, the Gastrocnemius gives the calf its bulged shape and plays an important role in walking and posture. Attaching to the femur and patella on top of the tibia, this muscle connects to the Achilles tendon at the heel. This muscle runs along the posterior of the leg helping in pulling the heel up as the foot is extended.

Soleus − Originating on top of the tibia and fibula, Soleus − the thinner muscle, runs along with the gastrocnemius and attaches to the Achilles tendon at the heel.

Plantaris − It’s a small muscle running along the back of the leg. Starting from just above the knee, it connects with the Achilles tendon and the heel bone.

The tibialis anterior connects the top of the tibia with the cuneiform and metatarsal bones of the foot. It runs along the front side of the leg helping the foot with dorsiflexion and inversion movements.

The tibialis posterior arises from the rear side of the tibia and fibula, running along the length of the lower leg it joins the navicular and cuneiform bones at the foot. Supporting the arch of the foot, it also helps in stabilizing the muscles.

Peroneus − A group of three muscles, namely, peroneus longus, peroneus brevis and peroneus tertius together form the peroneus muscles which run on the outside of the lower extremity. These are also known as the fibularis muscles. Together these muscles help in dorsiflexion and plantarflexion.

Achilles tendon − The Achilles tendon is the major tendon in the lower leg attaching the calf to the calcaneus (heel bone). It helps with the basic functions of the leg such as walking, and running and supports close to ten times the body weight

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The talus which forms the starting point of the ankle joint, at the base, extends to form the foot. A group of bones called tarsals, metatarsals and phalanges combine to form the foot.

Apart from providing stability, bones give shape and structure to our bodies. Bones also act as the production centre of blood. All these tiny and large structures of bones must work together for normal bodily functions and movements.

FAQs

Q1. What are the three main bones of the leg?

Ans. The femur, tibia and fibula are the main bones of the leg.

Q2. What are the three main axes at the hip joint?

Ans. The three main axes are the transverse axis, the longitudinal axis and the sagittal axis.

Q3. What are the main ligaments at the hip joint?

Ans. Iliofemoral ligament, pubofemoral ligament and ischiofemoral ligament

Q4. What are the joints at the knee called?

Ans. There are two main joints combined to form a joint capsule at the knee. They are called the tibiofibular joint and the patellofemoral joint.

Q5. What are the main ligaments of the knee?

Ans. Medial collateral ligament (MCL), lateral collateral ligament (LCL), anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial meniscus and the lateral meniscus

Q6. What are the main muscles of the lower leg?

Ans. The gastrocnemius, the soleus, and the plantaris form the main muscles of the lower leg.

raja
Updated on 13-Oct-2022 11:19:47

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