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 fibrocartilaginous 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 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 in the thigh which help in adduction, the action of pulling the leg back towards the midline.
- Iliopsoas: This muscle is 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 backwards.
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 the anatomical parts of the hip work together to enable various movements. Hip movements include flexion, extension, abduction, adduction, circumduction, and hip rotation.
Hip Injuries & Tears
Hip pain, one of the common symptoms patients complain of, may not always be felt precisely over the hip joint. Pain may be felt in and around the hip joint and the cause for pain is multifactorial. The exact position of your hip pain suggests the probable cause or underlying condition causing pain.
The hip labrum is a ring of strong fibro-cartilaginous tissue lining around the socket of the hip joint. Labrum serves many functions where it acts as shock absorber, lubricates the joint, and distributes the pressure equally. It holds the head of the femur in place and prevents the lateral and vertical movement of the femur head with in the joint. It also deepens the acetabular cavity and offers stability against femoral head translation.
Femoroacetabular impingement (FAI) is a condition where there is too much friction in the hip joint from bony irregularities causing pain and decreased range of hip motion. The femoral head and acetabulum rub against each other creating damage and pain to the hip joint. The damage can occur to the articular cartilage (the smooth white surface of the ball or socket) or the labral tissue (the lining of the edge of the socket) during normal movement of the hip.
Developmental dysplasia of the hip (DDH) is a common disorder that is seen in infants and young children. It may be present at birth or may occur during the first year of life of the infant. As the name suggests, it occurs due to improper development of the hip joint either while the fetus is in the uterus or during the growth phase in the first year of life.
Loose bodies are small loose fragments of cartilage or a bone that float around the joint. The loose bodies can cause pain, swelling, locking and catching of the joint. Loose bodies occur if there is bleeding within the joint, death of tissues lining the joints associated with tuberculosis, osteoarthritis, and rheumatoid arthritis. Other causes include fractures, trauma, bone and cartilage inflammation, and benign tumors of the synovial membrane.
Hamstring injuries are common in athletes who participate in sports activities such as track, soccer, and basketball that involve running. The three hamstring muscles namely semitendinosus, semimembranosus and biceps femoris are at the back of the thigh and helps you bend (flex) your knee and extend your leg.
Avascular necrosis, also called osteonecrosis is a condition in which bone death occurs because of inadequate blood supply to it. Lack of blood flow may occur when there is a fracture in the bone or a joint dislocation that may damage nearby blood vessels. Chronic use of high doses of steroid medications and heavy alcohol consumption are the two main risk factors of avascular necrosis. Initially, small breaks appear in the bone that may eventually collapse. Hip joint is most commonly affected; however, the knee and shoulder may also be involved.
The hip joint is one of the largest weight-bearing joints in the body, formed by the thigh bone or femur and the acetabulum of the pelvis. It is a ball and socket joint with the head of the femur as the ball and the pelvic acetabulum forming the socket. The joint surface is covered by a smooth articular cartilage which acts as a cushion and enables smooth movements of the joint. A chondral injury refers to an injury of the articular cartilage, covering the joint.
The hip plays an important role in supporting the upper body weight while standing, walking and running, and hip stability is crucial for these functions. The femur (thigh bone) and acetabulum (hip bone) join to form the hip joint, while the labrum (tissue rim that seals the hip joint) and the ligaments lining the hip capsule maintain the stability of the hip. Injury or damage to these structures can lead to a condition called hip instability. Hip instability happens when the hip joint becomes unstable causing various symptoms.
The hip joint consists of 2 bones, the hip bone and the leg bone. An injury or bruise to one of these bones or the surrounding muscles or tissues is termed a hip pointer. This type of injury is mainly caused due to a sudden blow or hit on the hip which can occur from sports activities such as football, rugby, volleyball, basketball, cycling or skating.
The hip is an important joint that helps us walk, run and jump. The ball-and-socket joint in the hip is formed between the round end of the femur (thighbone) and the cup-shaped socket of the acetabulum (part of the hip bone). Joint stability in the hip region is achieved through the labrum (a strong fibrous cartilage), which covers the acetabulum and seals it, and ligaments (tissue connecting bone to bone) and tendons (tissue connecting muscle to bone) that encase the hip and control the hip movements.
Hip joint injections involve injecting medicine directly into the hip joint to diagnose the source of pain or treat pain due to conditions such as labral tears of the hip joint. Hip pain may be experienced in the hip, buttock, leg or low back. The injection contains a combination of a numbing medicine and cortisone (an anti-inflammatory agent). Numbing medicine delivers temporary relief from pain, provided the hip joint is the source of the pain. It thus serves a diagnostic function and helps to confirm or deny whether the joint is the source of pain. Cortisone serves to reduce the inflammation in the joint providing long term pain benefit.
Physical therapy is an exercise program that helps you to improve movement, relieve pain, encourage blood flow for faster healing, and restore your physical function and fitness level. The main aim of physical therapy is to make your daily activities, such as walking, getting in and out of bed, or climbing stairs, easier. It can be prescribed as an individual treatment program or combined with other treatments. Physical therapy is usually ordered to help you recover after certain surgeries, injuries and long-term health problems such as arthritis.
Our blood consists of a liquid component known as plasma. It also consists of three main solid components which include the red blood cells (RBCs), white blood cells (WBCs), and platelets. Platelets play an important role in forming blood clots. They also consist of special proteins, known as growth factors, which help with our body’s healing process. Platelet-rich plasma or PRP is a high concentration of platelets and plasma.
The hip joint is a ball and socket joint, where the head of the thigh bone (femur) articulates with the cavity (acetabulum) of the pelvic bone.