1. BIO-MECHANICS OF HIP JOINT
Lecture-3
BIO-MECHANICS OF HIP JOINT
Prepared by:
Dr. Hazrat Bilal DPT (IPMR, KMU)

2. OBJECTIVES At the end of this lecture the students shall be able to:
Describe the joint stability and congruency
Enumerate capsule biomechanics
Identify different hip ligaments
Discus biomechanics of hip ligaments

3. STABILTY/CONGURANCY

4. Articular Congruence
The hip joint is considered to be a congruent joint.
However, there is actually more articular surface on the head of the femur than on the acetabulum.
In the neutral or standing position, the articular surface of the femoral head remains exposed anteriorly and somewhat superiorly

5. The acetabulum does not fully cover the head superiorly, and the anterior torsion of the femoral head (angle of torsion) exposes femoral head’s articular surface anteriorly.

6. Articular contact between the femur and the acetabulum can be increased in the normal non- weight-bearing hip joint by a combination of flexion, abduction, and slight lateral rotation
This position (also known as the frog-leg position) corresponds to that assumed by the hip joint in a quadruped position and, according to Kapandji, is the true physiologic position of the hip joint.

8. An additional contribution to articular congruence of joint surfaces may be made by the nonarticular and non-weight-bearing acetabular fossa.
The acetabular fossa may be important in setting up a partial vacuum in the joint so that atmospheric pressure contributes to stability by helping maintain contact between the femoral head and the acetabulum.

9. Wingstrand and colleagues concluded that atmospheric pressure in hip flexion activities played a stronger role in stabilization than capsuloligamentous structures.
It is also true that the head and acetabulum will remain together in an anesthetized patient even after the joint capsule has been opened. The pressure within the joint must be broken before the hip can be dislocated.
Gloria’s structural deviations of femoral anteversion,
coxa valga, and a shallow acetabulum (decreased CE
Chapter 10: The Hip Complex ■ 361 A B C
▲ Figure 10-8 ■ Abnormal angles of torsion in a right femur.
A. and B. A pathologic increase in the angle of torsion is called anteversion.
C. A pathologic decrease in the normal angle of torsion is
called retroversion.
▲ Figure 10-9 ■ A. In the neutral hip joint, articular cartilage
from the head of the femur is exposed anteriorly and, to a lesser
extent, superiorly. B. Maximum articular contact of the head of the
femur with the acetabulum is obtained when the femur is flexed,
abducted, and laterally rotated slightly.
angle) can result in increased articular exposure of the
femoral head, less congruence, and reduced stability
of the hip joint in the neutral weight-bearing position.

10. JOINT CAPSULE

11. Hip Joint Capsule
Unlike the relatively weak articular capsule of the shoulder, the hip joint capsule is a substantial contributor to joint stability.
The articular capsule of the hip joint is an irregular, dense fibrous structure with longitudinal and oblique fibers and with three thickened regions that constitute the capsular ligaments.

12. The capsule is attached proximally to the entire periphery of the acetabulum beyond the acetabular labrum.
Fibers near the proximal attachment are aligned in a somewhat circumferential manner.

13. The capsule itself is thickened anterosuperiorly, where the predominant stresses occur; it is relatively thin and loosely attached posteroinferiorly, with some areas of the capsule thin enough to be nearly translucent.
The capsule covers the femoral head and neck like a cylindrical sleeve and attaches to the base of the femoral neck.

14. The femoral neck is intracapsular, whereas both the greater and lesser trochanters are extracapsular.
The synovial membrane lines the inside of the capsule.
Anteriorly, there are longitudinal retinacular fibers deep in the capsule that travel along the neck toward the femoral head.
The retinacular fibers carry blood vessels that are the major source of nutrition to the femoral head and neck.

15. HIP LIGAMENTS

16. Hip Joint Ligaments
The ligamentum teres is an intra-articular but extrasynovial accessory joint structure. The ligament is a triangular band attached at one end to both sides of the peripheral edge of the acetabular notch.
The ligament then passes under the transverse acetabular ligament (with which it blends) to attach at its other end to the fovea of the femur; thus, it is also called the ligament of the head of the femur

17. The ligamentum teres is encased in a flattened sleeve of synovial membrane so that it does not communicate with the synovial cavity of the joint. The material properties of the ligament of the head are similar to those of other ligaments, and it is tensed in semiflexion and adduction.
However, it does not appear to play a significant role in joint stabilization regardless of joint position.

18. Rather, the ligamentum teres appears to function primarily is to supply secondary blood from the obturator artery and for the nerves that travel along the ligament to reach the head of the femur through the fovea.

20. The hip joint capsule is typically considered to have three reinforcing capsular ligaments (two anteriorly and one posteriorly), although some investigators have further divided or otherwise renamed the ligaments.
For purposes of understanding hip joint function, the following three traditional descriptions appear to suffice.
The two anterior ligaments are the iliofemoral ligament and the pubofemoral ligament.

21. The iliofemoral ligament is a fan-shaped ligament that resembles an inverted letter Y
It often is referred to as the Y ligament of Bigelow. The apex of the ligament is attached to the anterior inferior iliac spine, and the two arms of the Y fan out to attach along the intertrochanteric line of the femur. The superior band of the iliofemoral ligament is the strongest and thickest of the hip joint ligaments.
The pubofemoral ligament is also anteriorly located, arising from the anterior aspect of the pubic ramus and passing to the anterior surface of the intertrochanteric fossa.

25. The bands of the iliofemoral and the pubofemoral ligaments form a Z on the anterior capsule, similar to that of the glenohumeral ligaments. The ischiofemoral ligament is the posterior capsular ligament.
The ischiofemoral ligament attaches to the posterior surface of the acetabular rim and the acetabulum labrum.
Some of its fibers spiral around the femoral neck and blend with the fibers of the circumferential fibers of the capsule.
Other fibers are arranged horizontally and attach to the inner surface of the greater trochanter.

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