Functional Anatomy of the Hip-Bones and Ligaments
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Description[edit | edit source]
The hip joint is considered one of the largest joints of the human body. It connects the pelvis to the lower extremities. The primary roles of the hip joint are to allow lower extremities weight-bearing and to provide stability in standing and during mobility such as walking or running.
Structure[edit | edit source]
The hip joint is a ball-and-socket joint that provides stability for the body and sustains forces that can exceed the total body weight multiple times. This ability to accept a significant load is due to a combined work of the static and dynamic elements of the joint paired with a proper body alignment. The static stabilisers include bones, ligaments, capsule and bursae. Muscles, fascia, tendons, nerves and vascular supply are all dynamic elements of the hip joint. The movements that occur in this joint are:
- Sagittal plane: flexion/extension
- Frontal plane: abduction/adduction
- Transverse plane: medial/lateral rotation
Hip (thigh) circumduction is a movement performed in two planes: sagittal and frontal
Bones[edit | edit source]
The hip joint is made out of two bony structures: the acetabulum and the femoral head.
Acetabulum[edit | edit source]
The acetabulum is a lateral part of the pelvis. Its concave shape allows for the fitting of the femoral head. The femoral head is located at the proximal aspect of the femoral bone which distally connects to the tibia and the fibula.
What is referred to as a normal pelvis and acetabulum are in fact difficult to define.[1]A better understanding of the topographic map of the acetabulum is important for creating a good anatomic implant design when replacement or reconstruction of the acetabulum is needed. [1] The superior and posterior walls of the acetabulum are in anteversion and abduction. The face of the acetabulum has an average of 20.7 degrees of anteversion and 39.8 degrees of abduction. The anterior portion of the acetabulum is flat while the posterior portion is angled with its highest point at the sciatic notch. [1]
The margin of the acetabulum is 75% circle, except for its anteroinferior aspect called the acetabular notch. The transverse ligament of the hip closes the circle at this notch. This is where the acetabular labrum attaches allowing for an increase of the articular area of the acetabulum. Because of this anatomical structure, 50% of the femoral head can fit into the acetabulum. [2]
The acetabulum is divided into anterior and posterior columns. The anterior column includes the anterior ilium, anterior wall, the anterior dome of the acetabulum, and superior pubic ramus. The posterior column consists of greater and lesser sciatic notches, posterior wall, the posterior dome of the acetabulum, and ischial tuberosity.[2]
Femoral Head[edit | edit source]
Ligaments[edit | edit source]
The ligaments reinforcing the hip are divided into intra- articular and extra-articular. There are two intra-articular ligaments:
- Ligament of the femoral head is also called a round ligament of the femur, ligamentum teres femoris, or the foveal ligament. This ligament attaches between the peripheral inferior acetabular notch and the fovea of the femoral head. The main function includes carrying small vessels and innervations to the femoral head and providing proprioception and structural stability by limiting abduction and external rotation when the hip is flexed.
- Transverse ligament of the acetabulum is in fact a fibrous structure that transforms the acetabular notch into a foramen. It channels nerves and vessels into the joint.[3]
The extra-articular ligaments are primary hip joint stabilisers and they include:
- Iliofemoral ligament (also known as the Y ligament of Bigelow) contains lateral and medial fibrous branches. It stretches between the anterior inferior iliac spine/ the acetabular rim and the intertrochanteric line/ the greater trochanter. The primary function of this ligament is to prevent hip hyperextension in the upright position and external rotation. In addition, it serves as the anterior capsule reinforcer.
- Ischiofemoral ligament is the weakest of the four ligaments and consists of a triangular band of fibres that form the posterior hip joint capsule. It inserts in the ischium, behind the acetabulum and attaches to the femur, medial to the greater trochanter. The ligament has two roles: it limits internal rotation and extension and reinforces the posterior portion of the capsule during internal rotation.
- Pubofemoral ligament originates at the pubic part of the acetabular rim and the superior pubic ramus and attaches to the lower part of the femoral neck. It limits abduction and external rotation during hip extension and reinforces the inferior capsule.
- Zona orbicularis primary role is to stabilise the hip joint. This ligament is formed by the circular fibres from the capsule containing fibres from all extra-articular ligaments. [3]
Joint Capsule[edit | edit source]
Joint capsule is a supporting structure of the hip joint. It is fibrous
The capsule plays a significant role in the hip joint stability[4]The hip joint capsule contributes to the stability of the hip joint and lower extremity,
There is general agreement that Pacinian, Ruffini and Golgi corpuscles are present in the hip capsule of individuals with no known pathology and patients with OA
A greater density of Pacinian and Ruffini corpuscles appear to be present in the hip capsules of both healthy individuals [28] and patients with OA [28, 49] compared to other mechanoreceptors. These mechanoreceptors act to monitor vibration and tensile loading, respectively. However, it is unclear if individuals have more Pacinian or Ruffini corpuscles in their hip capsular complex. When comparing the changes in density of specific mechanoreceptors in the hip capsules of those with and without OA Pacinian corpuscles are more greatly reduced in the OA group compared to the healthy group than the reduction in Ruffini corpuscles [28]. This may have an effect on biomechanical functioning of the joint, but more research is required to confirm this.[5]
Bursae[edit | edit source]
Function[edit | edit source]
Clinical relevance[edit | edit source]
- Coxa profunda is a pathology related to an increased depth of the acetabular socket. This is a problem more commonly present in females.
- Acetabular retroversion refers to an abnormal posterior angulation of the superolateral acetabular rim. This pathology is causing the femoral head to be excessively covered and predisposes to femoroacetabular impingement. It is also considered a risk factor for the osteoarthritis of the hip.
- Development of larger cross-sectional areas and tighter capsular ligaments can be the result of progressive arthritis. [3]
- Surgical procedure involving capsular closure restores the biomechanics of the hip, a study has found. [4]
Resources[edit | edit source]
References[edit | edit source]
- ↑ 1.0 1.1 1.2 Krebs V, Incavo SJ, Shields WH. Tthe anatomy of the acetabulum: what is normal? Clin Orthop Relat Res. 2009 Apr;467(4):868-75. doi: 10.1007/s11999-008-0317-1. Epub 2008 Jul 22.
- ↑ 2.0 2.1 Bannai M, Rock P. Acetabulum. Reference article. Radiopaedia.org. Available at https://radiopaedia.org/articles/acetabulum (last access 20.02.2022).
- ↑ 3.0 3.1 3.2 Ng KCG, Jeffers JRT, Beaulé PE. Hip Joint Capsular Anatomy, Mechanics, and Surgical Management. J Bone Joint Surg Am. 2019 Dec 4;101(23):2141-2151.
- ↑ 4.0 4.1 Freeman KL, Nho SJ, Suppauksorn S, Chahla J, Larson CM. Capsular Management Techniques and Hip Arthroscopy. Sports Med Arthrosc Rev. 2021 Mar 1;29(1):22-27.
- ↑ Tomlinson J, Zwirner J, Ondruschka B, Prietzel T, Hammer N. Innervation of the hip joint capsular complex: A systematic review of histological and immunohistochemical studies and their clinical implications for contemporary treatment strategies in total hip arthroplasty. PLoS One. 2020 Feb 26;15(2):e0229128.
