Key Features of Hip Structure, Joint Angles, and Their Biological Roles
In anatomy, the hip is defined as the joint between the pelvis and thighbone (femur) and the area adjacent to this particular joint. To describe the hip joint, we can say that it has a structure of a ball-and-socket joint, where the round head of the femur rests in a cavity (also called the acetabulum), which allows free rotation of the limb. Various organisms contain different sized hip in body parts.
Hip - In Animals
Reptiles and amphibians contain relatively weak pelvic girdles, and the femur gets extend horizontally. This prevents the animals from effectively resisting gravity, and their trunks often rest partially on the ground. Whereas, in mammals, the hip joint allows the femur to drop vertically, hence permitting the animal to hold itself off the ground and leading to the specializations for leaping and running.
Hip Joint
Scientifically, the hip joint is known as the acetabulofemoral joint (art. coxae), which is the joint between the acetabulum and femur of the pelvis and its main function is to support the body weight in both dynamic (for example, running and walking) and static (for example, standing) postures. The hip joints contain very crucial roles in balance retaining and maintaining the angle of pelvic inclination.
The pain of the hip could be the result of numerous causes, including osteoarthritic, nervous, traumatic, infectious, and genetic.
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Structure
Region
The greater trochanter is frequently the only palpable bony structure in the hip region since the proximal femur is more heavily protected by muscles.
Articulation
To describe, the hip joint is a synovial joint formed by the rounded head of the cup-like acetabulum and the femur of the pelvis articulating together. It also forms the primary connection between the lower limb and the bones and the axial skeleton of the pelvis and trunk. Both the joint surfaces are covered with a strong but lubricated layer, which is known as hyaline articular cartilage.
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The above hip diagram represents a healthy human hip joint radiograph.
Articular Angles of Hip
The transverse angle of the acetabular inlet (which is also called Sharp's angle and it is generally the angle called acetabular angle without further specification) is described by measuring the angle between a line passing from the superior to the horizontal plane and inferior acetabular rim; an angle that normally measures 51° in infants and 40° in adults that affects the lateral acetabular coverage of the femoral head and many other parameters.
Wiberg's centre-edge angle (which is called CE angle) is defined as an angle between a line from the centre of the femoral head and the vertical line to the most lateral part of the acetabulum, which can be seen on an anteroposterior radiograph.
The sagittal angle of the acetabular inlet is described as an angle between a line that passes from the anterior to the sagittal plane and the posterior acetabular rim. in adults; it also measures 7° at birth and increases to 17°.
Femoral Neck Angle
The angle which lies between the longitudinal axes of the shaft and femoral neck is called the caput-collum-diaphyseal angle or simply CCD angle, generally measures nearly 150° in newborn and as 126° in adults (which is called as coxa norma).
An abnormally large angle is called coxa valga and an abnormally small angle, as coxa vara. Since changes in femur shape affect the knee, coxa valga is often associated with genu varum (also known as bow-leggedness), while coxa vara causes genu valgum (knock-knees).
Capsule
The capsule usually attaches to the hip bone that is outside the acetabular hip, which therefore projects into capsular space. Whereas, on the femoral side, the distance between the cartilaginous rim head and the capsular attachment at the neck's base is constant that leaves a wider extracapsular neck part at the back than at the front.
The strong but loose fibrous capsule present on the hip joint permits the hip joint to contain the second-largest range of movement (which is second, only to the shoulder) and yet supports the weight of the arms, body, and head.
Ligaments
The hip joint is the one, which is reinforced by four ligaments, where three are extracapsular and one is intracapsular.
The extracapsular ligaments are given as the ischiofemoral, iliofemoral, and pubofemoral ligaments that are attached to the pelvis bones (the ischium, ilium, and pubis, respectively). All these three strengthen the capsule and prevents an excessive range of joint movement. The iliofemoral ligament, which is twisted and Y-shaped, is the strongest ligament in the human body or the hip in the human body. It also stops the trunk from dropping backwards in the upright position without the need for muscular action. In the sitting position, it becomes relaxed, allowing the pelvis to tilt backwards into the sitting position.
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Blood Supply
The lateral circumflex femoral arteries and the medial circumflex femoral arteries, which are both generally branches of the deep artery of the thigh (also known as profunda femoris), supply blood to the hip joint. However, there are a number of variations, and either one or both can also arise directly from the femoral artery.
FAQs on Hip Anatomy and Its Importance in Biology
1. What part of the body is the hip and where is it located?
The hip is the area on each side of the pelvis, between the upper part of the thigh bone and the waist. It contains the hip joint, which is the crucial connection point between your leg (femur) and your torso (pelvis). This joint is one of the largest and most important weight-bearing joints in the body.
2. What bones make up the hip joint?
The hip joint is formed by the interaction of two main bones. It consists of the rounded head of the femur (the thigh bone) fitting into a cup-shaped socket in the pelvis known as the acetabulum. This structure creates a strong and stable ball-and-socket joint.
3. What are the main functions of the hip joint in daily life?
The hip joint performs two critical functions. First, it supports the weight of the upper body during activities like standing, walking, and running. Second, it provides a wide range of motion for the legs, including:
- Bending forward and backward
- Moving the leg to the side and back to the centre
- Rotating the leg inwards and outwards
4. How is the hip bone different from the hip joint?
It's easy to confuse these terms. The hip bone (or innominate bone) is the large, flat bone that forms part of the pelvis. The hip joint, on the other hand, is the functional structure where the hip bone connects with the thigh bone (femur). So, the hip bone is a major component that helps form the hip joint.
5. Why is the female hip structure generally different from the male hip structure?
The female hip is typically wider and has a larger, more circular pelvic opening compared to the male hip. This key difference, known as sexual dimorphism, is a biological adaptation to facilitate childbirth. The male pelvis is generally heavier, taller, and more compact, which is suited for supporting a more muscular build.
6. Why is the hip classified as a 'ball-and-socket' joint, and what is the benefit of this design?
The hip is called a ball-and-socket joint because the 'ball' at the top of the femur fits securely into the 'socket' of the pelvic acetabulum. The major benefit of this design is its incredible range of motion. It allows for movement in multiple directions—forwards, backwards, sideways, and rotational—giving us the flexibility needed for complex activities like walking, squatting, and dancing.
7. What are some examples of common health issues related to the hip?
Because the hip bears a lot of weight and stress, it can be prone to certain issues. A common example is osteoarthritis, a condition where the protective cartilage wears down over time, causing pain and stiffness. Another significant issue is a hip fracture, which is a break in the upper part of the femur and is more common in older individuals with weaker bones.
