Hip Joint Pain-causes

The hip joint attaches the leg to the torso of the body. In the hip joint, the head of the thighbone (femur) swivels in a socket, called the acetabulum, that is made up of pelvic bones. While many causes of hip pain can arise from the joint itself, there are numerous structures surrounding the hip that can also be the source of pain.

Trauma is often the cause of hip pain, but any source of inflammation may cause pain in the hip area. Pain is one of the symptoms of inflammation, along with swelling, warmth, and redness; together these are signals that a problem may exist.


Hip Pain Causes

Pain can arise from structures that are within the hip joint or from structures surrounding the hip. The hip joint is a potential space, meaning that there is a minimal amount of fluid inside it to allow the femoral head to glide in the socket of the acetabulum. Any illness or injury that causes inflammation will cause this space to fill with fluid or blood, which stretches the hip capsule and results in pain.

The femoral head and the acetabulum are lined with articular cartilage that allows the bones to move within the joint with less friction. Also, the socket area of the acetabulum is covered with tough cartilage called the labrum. Just like any other joint cartilage, these areas can wear away or tear and become the source of pain.

There are thick bands of tissue that surround the hip joint, forming a capsule. These help maintain joint stability, especially with movement.

Movement at the hip joint is possible due to the muscles that surround the hip and their tendons that attach across the hip joint, allowing motion in different directions. Aside from controlling movement, these muscles act in concert to maintain joint stability. There are large bursas (closed fluid-filled sacs) that surround areas of the hip and allow the muscles and tendons to glide more easily over bony prominences. Any of these structures can become inflamed.

Pain from other sources can be referred to the hip, meaning that while the hip hurts, the problem may potentially originate elsewhere. Inflammation of the sciatic nerve as it arises from the spinal cord in the back can cause hip pain, especially if the L1 or L2 nerve roots are involved. Other types of nerve inflammation may manifest as hip pain, including pain arising in the lateral femoral cutaneous nerve of the thigh, which is often inflamed in pregnancy. Pain from an inguinal hernia may also cause pain that is felt in the hip.

Hip pain is a nonspecific complaint that requires the health-care practitioner to find the underlying cause, from injury to illness. Without specific trauma, the approach to the diagnosis of hip pain requires an open mind.


causes of Traumatic Hip Pain

Hip Fracture

Falls are the most common reason that elderly people break a hip. The fracture is due to a combination of two effects of aging, osteoporosis (thinning of bones) and a loss of balance. These two risk factors often precipitate many falls. Occasionally, the bone may spontaneously break due to osteoporosis and become the cause of the fall.

When health-care practitioners talk about a hip fracture, they really mean a fracture of the proximal or upper part of the femur.

The precise location of the fracture is important, because it guides the decision of the orthopedic surgeon as to which type of operation is needed to repair the injury.

Aside from a fall, any trauma can potentially cause a hip fracture. Depending upon the mechanism of injury, the femur may not break; rather, a portion of the pelvis (often the pubic ramus) may be fractured. The initial pain may be in the hip area, but examination and X-rays may reveal a different source of the injury. Trauma can also cause a hip dislocation in which the femoral head loses its relationship with the acetabulum. This is almost always associated with an acetabular (pelvic bone) fracture; however, in patients with hip replacements, the artificial hip may dislocate spontaneously.



Contusions (Bruises)

Contusions (bruises), sprains, and strains may occur as a result of trauma, and even though there is no broken bone, these injuries can still be very painful. Sprains are due to ligament injuries, while strains occur because of damage to muscles and tendons. Because of the amount of force required to walk or jump, the hip joint is required to support many times the weight of the body. The muscles, bursas, and ligaments are designed to shield the joint from these forces. When these structures are inflamed, the hip cannot function and pain will occur.

Overuse Injuries

Hip pain may also arise from overuse injuries in which muscles, tendons, and ligaments can become inflamed. These injuries may be due to routine daily activities that may cause undue stress on the hip joint or because of one specific strenuous event. Overuse may also cause gradual wearing away of the cartilage in the hip joint, causing arthritis (arth=joint + itis=inflammation).

Other structures should be mentioned as a cause of hip pain because they become inflamed. The iliotibial band stretches from the crest of the pelvis down the outside part of the thigh to the knee. This band of tissue may become inflamed and cause hip pain, knee pain, or both. This is a type of overuse injury that has a gradual onset associated with tightness of the muscle groups that surround the knee and hip. Piriformis syndrome, in which the piriformis muscle irritates the sciatic nerve in the buttock, can also cause significant posterior hip pain.

Bursa Inflammation (Hip Bursitis)

The trochanteric bursa is a sac on the outside part of the hip that serves to protect muscles and tendons as they cross the greater trochanter (a bony prominence on the femur). Trochanteric bursitis describes the inflammation of this bursa. The bursa may become inflamed for a variety of reasons, often due to minor trauma or overuse.
Causes of Nontraumatic Hip Pain

Hip pain may be caused by a variety of illnesses. Anything that causes systemic inflammation in the body may also affect the hip joint. The synovium is a lining tissue that covers those parts of the hip joint not covered by cartilage. Synovitis (syno=synovium + itis= inflammation), or inflammation of this lining tissue, causes fluid to leak into the joint, resulting in swelling and pain.

Arthritis

Osteoarthritis is the most common cause of hip pain in those over the age of 50; however, other types of arthritis can be present. These may include
rheumatoid arthritis,
ankylosing spondylitis,
arthritis associated with inflammatory bowel disease (Crohn's disease or ulcerative colitis).
Some systemic diseases are associated with hip pain, including sickle cell disease, in which a joint may swell during a sickle crisis either with or without an underlying infection. The hip joint is not the only joint that may be involved.
Viral or bacterial infections may cause hip inflammation. Examples include Lyme disease, Reiter's syndrome, and infections caused by food poisoning.
Avascular necrosis of the femoral head may occur in people who have taken corticosteroid medications like prednisone for a prolonged period of time. In this condition, the femoral head loses its blood supply, becomes weakened, and causes hip pain.
Legg-Calvé-Perthes disease (or just Perthes disease) describes avascular necrosis of the femoral head in children and is idiopathic, meaning the cause is unknown. It usually affects males between the ages of 4 and 8.
Fibromyalgia is a systemic pain syndrome associated with pain and stiffness that can cause significant discomfort throughout the body and may present as hip pain. There may be associated sleep disorders, muscle cramps and spasms, tenderness of a variety of muscle groups in the whole body, and fatigue.
Referred Hip Pain

Hip pain may not originate in the hip itself but may be caused by problems in adjacent structures.

A hernia or defect of the abdominal wall may cause pain in the front part of the hip. A hernia occurs when there is a weakness or tear in an area where muscles of the abdominal wall come together. They are named according to their location; inguinal (groin) hernias are most common.
Nerve branches can become inflamed to cause hip pain. Meralgia paresthetica occurs when the lateral femoral cutaneous nerve of the thigh becomes irritated. This condition is seen most commonly in pregnancy, in people wearing tight clothes, or in people with diabetes.
Sciatica, or inflammation of nerve roots from the spinal cord, may also present with hip pain. There are a variety of reasons for the sciatic nerve to become inflamed, including spinal stenosis due to osteoarthritis of the lumbar spine, ruptured or bulging disks in the vertebral column of the back, and spasms of the muscles that support the low back. Piriformis syndrome describes sciatic nerve inflammation that causes buttock and posterior hip pain due to sciatic nerve irritation as it travels through the buttock muscles.
Special Considerations for Children

Children who complain of leg or hip pain should not be ignored. If the pain is persistent, if a limp is present, or if the child has a fever, a health-care practitioner should be contacted.

Potential concerns in children with hip pain include

a slipped capital femoral epiphysis, a condition in which the bone growth plate of the femoral head shifts out of place,
Legg-Calvé-Perthes disease, or avascular necrosis of the femoral head,
juvenile rheumatoid arthritis, or Still's disease.
If a fever is present, septic arthritis or an infection of the hip joint may be present. This may be due to a virus or bacteria. Symptoms include fever, pain, limping, and sometimes refusal to walk. Viral infections are the most common cause of synovitis in infants and. resolve without treatment. If the care provider is concerned that the cause of synovitis may be a bacterial infection, urgent orthopedic consultation and evaluation may be needed in this situation.