Lecture 1 Biomechanics of the Hip Joint, Fall 2024, GALALA University PDF

Kinesiology 2 F a l l 2 0 2 4 T H E F U T U R E S T A R T S H E R E  G A L A L A U N I V E R S I T Y T H E F U T U R E S T A R T S H E R E T H E F U T U R E S T A R T S...

Kinesiology 2 F a l l 2 0 2 4 T H E F U T U R E S T A R T S H E R E  G A L A L A U N I V E R S I T Y T H E F U T U R E S T A R T S H E R E T H E F U T U R E S T A R T S H E R E The innominate bone contributes the proximal articular surface of the hip. The two innominate bones (right and left) together form the bony pelvis. It is located on the lateral aspect of the innominate bone, the acetabulum comprises the Y-shaped junction of the ilium, ischium, and pubis, which forms a deep, spherical socket that holds the head of the femur. The acetabulum faces laterally and slightly inferiorly. A fibrocartilaginous ring, or labrum, deepens the acetabulum, which helps to stabilize the hip joint, increase contact area, and decrease joint stress. These functions are fulfilled while avoiding a loss of mobility since the increased surface area is a compressible ring. Additionally, the acetabular labrum appears to seal a pressurized layer of synovial fluid that may protect the articular surfaces from damage. The shallow acetabulum at birth is an important risk factor for congenital hip dislocation. The femur, normally the largest bone of the body, is composed of a head, neck, and shaft, or body, which ends distally in the femoral condyles. The head of the femur provides the distal articular surface of the hip joint. The femoral head is covered with articular cartilage throughout its surface, with the exception of a small pit (fovea of the head of the femur) on its posteromedial aspect where the ligamentum teres attaches. The head of the femur in the adult forms approximately two thirds of a sphere, although its surface is not actually perfectly spherical. The articular cartilage on the femoral head provides a more spherical shape to the articular surface. The femoral neck extends laterally and posteriorly from the head of the femur and is almost entirely enclosed by the hip joint capsule. The orientation of the head and neck of the femur, like that of the acetabulum, influences hip excursion and weight bearing. An anterior view of the femur reveals that the femoral head faces medially and superiorly in the acetabulum. In the frontal plane, the angle of inclination refers to the approximately 125° angle between the neck of the femur and the shaft of the femur. Anteversion angle Cancellous bone extends from the shaft of the femur to the neck and head of the femur in organized arrays within the intertrochanteric region and along the superior and inferior aspects of the neck. The arrangement of cancellous bone in the femur also provides chock absorbing capacity. The greater trochanter is a large prominence on the proximal end of the femoral shaft. It is readily palpable about a hand’s length distance distal to the iliac crest. It gives rise to several muscles, including the large gluteal muscles. The location of the greater trochanter distal to the femoral neck lengthens the mo me n t a r m s o f t h e a t t a c h e d m u s c l e s , i m p r o v i n g t h e i r mechanical advantage to generate joint moments. The lesser trochanter is posteromedial on the proximal femoral shaft and provides distal attachment for the iliopsoas tendon. Separating the two trochanters posteriorly is the intertrochanteric crest. At the proximal aspect of the crest is the quadrate tubercle. Distal to the crest and greater trochanter is the gluteal tuberosity. The hip joint is a synovial, ball-and-socket. To meet its antagonistic functions of stability and mobility, the hip has its own unique articular structures including its ligaments and fibrocartilaginous expansion, the labrum. The relative orientation of the proximal femur and acetabulum also influences the mobility and stability available at the hip joint. As a synovial joint, the hip is supported by a synovial capsule that is attached to the bony rim of the acetabulum proximally and to the intertrochanteric crest and line of the femur distally. The capsule of the hip joint is composed primarily of fibers running parallel to its length, the longitudinal fibers. The capsule encloses most of the femoral neck and the entire femoral head. The blood supply to synovial joints is generally provided by a network of blood vessels, or anastomoses, at the attachment of the capsule and bone. Ligaments of the hip joint: The hip joint capsule is reinforced anteriorly by three longitudinal bundles of fibers, the iliofemoral, ischiofemoral, and pubofemoral ligaments, and the first two being the most consistent and strongest. The iliofemoral ligament arises not only from the iliac portion of the acetabulum but also from the anterior inferior iliac spine (AIIS). It proceeds in two parts along the anterior and superior aspects of the joint, creating the image of a Y, with its base directed toward the AIIS, and its top directed inferolaterally toward the intertrochanteric line. This ligament prevents excessive extension and lateral rotation ROM of the hip joint. In addition, the superior portion limits adduction ROM. The iliofemoral ligament appears to be the strongest ligament of the hip joint, sustaining larger tensile forces before rupturing. The ischiofemoral ligament attaches to the ischial portion of the rim of the acetabulum. A portion of the ligament runs horizontally, reinforcing the capsule posteriorly. Another portion projects superiorly, spiraling over the superior aspect of the femoral neck to attach to the superior and medial aspects of the greater trochanter. These spiral fibers, like the iliofemoral and pubofemoral ligaments, limit excessive hyperextension. The posterior fibers limit medial rotation of the hip. The ischiofemoral ligament also limits adduction ROM when the hip is flexed. The pubofemoral ligament originates from the pubic portion of the acetabular rim and from the superior pubic ramus. It extends along the inferior aspect of the capsule. It, too, limits excessive extension ROM. Additionally, it helps to prevent too much a b d u c t i o n R O M Hip joint stability: The hip is stabilized by and then by its and. These ligaments consist of longitudinal and circumferential fibers criss-crossing one another. As the hip is extended, the fibers of the capsule clamp down on the bony contents within, firmly holding the femoral head in the acetabulum. In contrast, hip flexion slackens the joint capsule. Alignment of the articulating surfaces: In the normal erect posture, the acetabulum and femoral head are aligned so that the head of the femur is directed slightly anteriorly and superiorly in the acetabulum. This orientation exposes the anterior aspect of the femoral head, leaving a large articular surface available for movement toward flexion. The orientation of the femur and acetabulum facilitates advancement of the thigh in front of the trunk (flexion), while limiting the potential for backward movement of the thigh beyond the trunk.. Medial rotation ROM appears greater in women and adduction appears greater in men, but other motions appear similar. Aging appears to produce a clinically insignificant reduction in hip ROM in all directions, at least until the age of 80. Consequently, significant decreases in ROM suggest the existence of a joint impairment. ROM measurements of the hip are usually taken with the lower extremity functioning in an open chain, in which the femur is moved with respect to the pelvis. However, in daily life, the lower extremity functions frequently in a closed chain, so that the pelvis moves on the femur. In upright standing with the femur fixed, an anterior pelvic tilt flexes the hip, since the pelvic motion brings the anterior aspect of the pelvis closer to the femur; a posterior pelvic tilt on a fixed femur extends the hip. When the pelvis is elevated on one side in the frontal plane and the lower extremity remains fixed, the lateral aspect of the pelvis on the opposite side moves closer to its respective femur. Interaction of the hip joint and lumbar spine in hip motion: Hip joint motion is measured by determining the position of the thigh relative to the trunk. Unless care is taken to control the movement of the pelvis and thus the lumbar spine, the measured movements may actually reflect both hip and spine motion.Trunk side bending and pelvic movement in the frontal plane can appear to be hip abduction or adduction motion. It is important to recognize the pelvic and femoral contributions to hip motion may occur simultaneously, not just sequentially. Therefore, considerable care is needed to distinguish true hip motion from apparent hip motion coming from the pelvis and low back Hip motion in activities of daily living: Hip motion is essential to many daily activities, including , , , and. Normal walking utilizes approximately 20–30º of flexion, reaching a maximum at about initial contact. Stair climbing utilizes more, approximately 45–65º and slightly less for stair descent. Rising from a chair typically requires more than 100º of hip flexion, usually less than the amount of flexion used when bending to tie a shoe or squatting to pick up something from the floor.  G A L A L A U N I V E R S I T Y T H E F U T U R E S T A R T S H E R E T H E F U T U R E S T A R T S H E R E