text: The hip joint is the largest weight-bearing joint in the human body. It is also referred to as a ball and socket joint and is surrounded by muscles, ligaments, and tendons. The thigh bone or femur and the pelvis join to form the hip joint.
  Any injury or disease of the hip will adversely affect the joint's range of motion and ability to bear weight.
  The hip joint is made up of the following:
  - Bones and joints
  - Ligaments of the joint capsule
  - Muscles and tendons
  - Nerves and blood vessels that supply the bones and muscles of the hip
  Bones and Joints
  The hip joint is the junction where the hip joins the leg to the trunk of the body. It is comprised of two bones: the thigh bone or femur and the pelvis which is made up of three bones called ilium, ischium, and pubis. The ball of the hip joint is made by the femoral head while the socket is formed by the acetabulum. The Acetabulum is a deep, circular socket formed on the outer edge of the pelvis by the union of three bones: ilium, ischium, and pubis. The lower part of the ilium is attached by the pubis while the ischium is considerably behind the pubis. The stability of the hip is provided by the joint capsule or acetabulum and the muscles and ligaments which surround and support the hip joint.
  The head of the femur rotates and glides within the acetabulum. A fibrocartilagenous lining called the labrum is attached to the acetabulum and further increases the depth of the socket.
  The femur or thigh bone is one of the longest bones in the human body. The upper part of the thigh bone consists of the femoral head, femoral neck, and greater and lesser trochanters. The head of the femur joins the pelvis (acetabulum) to form the hip joint. Next, to the femoral neck, there are two protrusions known as greater and lesser trochanters which serve as sites of muscle attachment.
  Articular cartilage is the thin, tough, flexible, and slippery surface lubricated by synovial fluid that covers the weight-bearing bones of the body. It enables smooth movements of the bones and reduces friction.
  Ligaments are fibrous structures that connect bones to other bones. The hip joint is encircled with ligaments to provide stability to the hip by forming a dense and fibrous structure around the joint capsule. The ligaments adjoining the hip joint include:
  Iliofemoral ligament: This is a Y-shaped ligament that connects the pelvis to the femoral head at the front of the joint. It helps in limiting the over-extension of the hip.
  Pubofemoral ligament: This is a triangular shaped ligament that extends between the upper portion of the pubis and the iliofemoral ligament. It attaches the pubis to the femoral head.
  Ischiofemoral ligament: This is a group of strong fibers that arise from the ischium behind the acetabulum and merge with the fibers of the joint capsule.
  Ligamentum teres: This is a small ligament that extends from the tip of the femoral head to the acetabulum. Although it has no role in hip movement, it does have a small artery within that supplies blood to a part of the femoral head.
  Acetabular labrum: The labrum is a fibrous cartilage ring which lines the acetabular socket. It deepens the cavity, increasing the stability and strength of the hip joint.
  Muscles and Tendons
  A long tendon called the iliotibial band runs along the femur from the hip to the knee and serves as an attachment site for several hip muscles including the following:
  Gluteals: These are the muscles that form the buttocks. There are three muscles (gluteus minimus, gluteus maximus, and gluteus medius) that attach to the back of the pelvis and insert into the greater trochanter of the femur.
  Adductors: These muscles are located in the thigh which helps in adduction, the action of pulling the leg back towards the midline.
  Iliopsoas: This muscle is located in front of the hip joint and provides flexion. It is a deep muscle that originates from the lower back and pelvis and extends up to the inside surface of the upper part of the femur.
  Rectus femoris: This is the largest band of muscles located in front of the thigh. They also are hip flexors.
  Hamstring muscles: These begin at the bottom of the pelvis and run down the back of the thigh. Because they cross the back of the hip joint, they help in extension of the hip by pulling it backward.
  Nerves and Arteries
  Nerves of the hip transfer signals from the brain to the muscles to aid in hip movement. They also carry the sensory signals such as touch, pain, and temperature back to the brain.
  The main nerves in the hip region include the femoral nerve in the front of the femur and the sciatic nerve at the back. The hip is also supplied by a smaller nerve known as the obturator nerve.
  In addition to these nerves, there are blood vessels that supply blood to the lower limbs. The femoral artery, one of the largest arteries in the body, arises deep in the pelvis and can be felt in front of the upper thigh.
  All of the anatomical parts of the hip work together to enable various hip movements. Hip movements include flexion, extension, abduction, adduction, circumduction, and hip rotation.
  The inflammation of the joints is referred to as arthritis. Inflammation arises when the smooth lining called cartilage at the ends of bones wears away. In some cases, the inflammation is caused when the lining of the joint becomes inflamed as part of an underlying systemic disease.
  The gluteal muscles (situated in the buttocks) are necessary for the stability and movement of the hip joints. The tendons of two gluteal muscles (gluteus medius and gluteal minimus) are attached at the outer hip region and are often called the “rotator cuff of the hip.”
  A hip fracture is a break that occurs near the hip in the upper part of the femur or thighbone. The thighbone has two bony processes on the upper part - the greater and lesser trochanters. The lesser trochanter projects from the base of the femoral neck on the back of the thighbone.
  Fractures to the femoral neck can completely or partially disconnect the femoral head from the rest of the femur. Femoral neck fractures may be either displaced, where the bone is moved out of its original position, or non-displaced, where there is no instability of the bone.
  Stress fractures of the hip are a break in the upper part of the thigh bone (femur) that fits into the socket of the hip joint. It can occur in any part of the hip, however, it mostly occurs just below the ball of the ball-and-socket hip joint called the femoral neck.
  Hip flexor pain is a distressing feeling or discomfort noted in the hip and/or groin region that can make everyday activities, such as going up and down the stairs or lifting your leg to tie a shoe extremely difficult and painful and can severely limit your activity and mobility.
  Transient osteoporosis of the hip is a rare condition that causes temporary bone loss in the upper region of the thighbone (femur). It occurs most often in young or middle-aged men of the age groups 30 to 60, and women in their later stages of pregnancy or early postpartum (following childbirth).
  Hip replacement surgery is one of the most common orthopedic surgeries performed. It involves the replacement of the damaged hip bone (ball shaped upper end of the femur) with a ceramic ball attached to a metal stem that is fixed into the femur and placing a new cup with a special liner in the pelvis.
  For a successful total hip replacement, accurate positioning of the implants is crucial to accomplish a good clinical outcome. Computer-navigated total hip replacement is an advanced technology developed to provide more accurate positioning of an implant.
  Custom total hip replacement, also called bespoke hip replacement or patient-specific hip replacement, is a newer, more advanced technology in total hip arthroplasty that uses an individualized hip implant for the replacement of the damaged or injured components of the hip joint.
  Avascular necrosis commonly affects the head of the femur. Necrosis leads to tiny cracks in the bone which finally causes the head of the femur to collapse.
  Sacroiliac joints (SI joint) are joints in the lower back region, where the sacrum and ilium bones join. Even though these joints are small and have limited motion, they have an important role in connecting your spine to the pelvic bone and the lower part of your body.