Hip Joint Flashcards
What type of joint is the hip joint?
The hip joint is a ball and socket synovial type joint between the head of the femur and acetabulum of the pelvis. It joins the lower limb to the pelvic girdle. The hip joint is designed to be a stable weight bearing joint. To achieve this, a large range of movement is sacrificed for stability.
What are the articulating surfaces of the hip joint?
The hip joint consists of an articulation between thehead of femur and acetabulum of the pelvis.
The acetabulum is a cup-like depression in the lateral side of the pelvis (much like the glenoid fossa of the scapula). The head of femur is hemispherical, and fits completely into the concavity of the acetabulum.
Both the acetabulum and head of femur are covered in articular cartilage, which is thicker at the places of weight bearing.
Describe the ligaments of the hip joint
Intracapsular:
The only intracapsular ligament is the ligament of head of femur. It is a relatively small ligament that runs from the acetabular fossa to the fovea of the femur. It encloses a branch of the oburator artery, which comprises a small proportion of the hip joint blood.
Extracapsular:
Iliofemoral: Located anteriorly. It originates from the ilium, immediately inferior to the anterior inferior iliac spine.The ligament attaches to the intertrochanteric line in two places, giving the ligament a Y shaped appearance. It prevents hyperextension of the hip joint.
Pubofemoral: Located anteriorly and inferiorly. It attaches at the pelvis to the iliopubic eminance and obturator membrane, and then blends with the articular capsule. It prevents excessive abduction and extension.
Ischiofemoral: Located posteriorly. It originates from the ischium of the pelvis and attaches to the greater trochanter of the femur. It prevents excessive extension of the femur at the hip joint.
Describe the neurovascular supply to the hip joint
-Vascular supply to the hip joint is achieved via the medial and lateral circumflex femoral arteries, and the artery to head of femur.
The circumflex arteries are branches of the profunda femoris artery. They anastamose at the base of the femoral neck to form a ring, from which smaller arteries arise to the supply the joint itself.
The medial circumflex femoral artery is responsible for the majority of the arterial supply (the lateral circumflex femoral artery has to penetrate through the thick iliofemoral ligament to reach the hip joint). Damage to the medial circumflex femoral artery can result in avascular necrosis of the femoral head.
The hip joint is innervated by the femoral nerve, obturator nerve, superior gluteal nerve, and nerve to quadratus femoris.
Describe the stabilising factors of the hip joint
The primary function of the hip joint is to bear weight. There are various structures present that increase its stability.
The first structure is the acetabulum. It is deep, and encompasses nearly all of the head of the femur. This decreases the probability of the head slipping out of the acetabulum, and causing a dislocation.
There is a fibrocartilaginous collar around the acetabulum which increases its depth. It is known as the acetabular labrum. The increase is depth provides a large articular surface , thus improving the stability of the joint.
The iliofemoral, pubofemoral and ischiofemoral ligaments are very strong, and along with the thickened joint capsule, they stabilise the joint greatly. These ligaments have a unique spiral orientation; this causes them to become tighter when the joint is extended, which adds stability to the joint, and also means less energy is needed to maintain a standing position.
Muscles and ligaments work in a reciprocal fashion at the hip joint:
Anteriorly, where the ligaments are strongest, the medial flexors (located anteriorly) are fewer and weaker.
Posteriorly, where the ligaments are weakest, the medial rotators are greater in number and stronger – they effectively ‘pull’ the head of the femur into the acetabulum.
Describe movements at the hip
Flexion: Iliosoas, rectus femoris, sartorius
Extension: Gluteus maximus, semimembranous,semitendinosus and biceps femoris
Abduction: Gluteus medius, gluteus minimus and the deep gluteals (piriformis, gemelli etc)
Adduction: Adductors longus, brevis and magnus,pectineus and gracillis
Lateral rotation: Biceps femoris, gluteus maximus, and the deep gluteals (piriformis, gemelli etc)
Medial rotation: Gluteus medius and minimus, semitendinosus and semimembranosus
The degree to which flexion at the hip can occur depends on whether the knee is flexed, which relaxes the hamstrings, and increases the range of flexion.
Extension at the hip joint is limited by the joint capsule, and in particular, the iliofemoral ligament. These structures become taut during extension to limit further movement.
Can you label the osteology of the anterior side of the hip
Can you label the osteology of the posterior side of the hip?
Can you label the hip bone as seen from the side?
Formed by fusion of 3 bones – Ilium
– Ischium
– Pubis
Separated by Tri-radiate cartilage
– Begins to fuse at 15-17 years
– Fusion complete by 20-25 years
What are some characteristics of the acetabulum?
- Where hip bones converge
- Margin of acetabulum is incomplete inferiorly- Acetabular notch
Fibrocartilaginous rim attached to margin of acetabulum:
- Increases the articular contact area by 10% – More than 50% of head of femur fits in
- Transverse acetabular ligament strengthens inferior portion of acetabulum where the acetabular notch is
