Hip

toc =Hip Joint= In the human body, many different joints are formed, which give th body the amazing ability to function as it does. A __joint__ is simply the location at where two or more bones make contact. As a result, the joints of the body are able to make a great amount of movement possible from something as simply as picking up a ball or running a marathon. One of the best ways to think of joints, are to imagine them acting almost like machines. The joints in your bodies are extremely powerful, and the one that will be focused on the most will be the hip joint. =Pelvis= The pelvis is a ring of bones in the lower trunk of the body, which is bounded by the [|coccyx (tail bone)] and the hip bones. The pelvis protects abdominal organs such as the bladder, rectum and, in women, the uterus. The pelvis is made up of three hip bones, which are joined by rigid sacroilac joints to the sacrum at the back. The hip bones curve forward to join the pubic symphysis at the front. The [|symphysis pubis] is a cartilaginous union between both sides of the pelvis anteriorly. It is significant during childbirth as it is capable of stretching to permit delivery. Attached to the pelvis are muscles of the abdominal wall, the buttocks, the lower back, and the insides and backs of the thighs. Each innominate bone is made up of three fused bones: the [|ilium], the ischium, and the pubis. Together they form the acetabulum which is a cup-like depression ball and socket joint. The ilium is the uppermost and largest and consists of a wide, flattened plate with a long curved ridge (called the "iliac crest") along its border. The pubis is the smallest pelvic bone. It extends forward from the ischium and around to the pubis symphysis, where it is joined to the other pubic bone by a tough, fibrous tissue. These three bones meet to form a cup-shaped cavity that make up the socket of the hip joint. There are many structural differences between the male and the female pelvis, most of which reflect the role of childbirth in the female. The male pelvis is larger and smaller inside with the pubis symphysis deeper and longer. The female, on the other hand, has a much more delicate, less prominent pelvis that is wider inside and the pubis symphysis shallow and shorter. =Femur= The "femur" is the thigh bone, the longest bone in the body. The lower end joins the tibia (shin) to form the knee joint. The upper end is rounded into a ball (or "head" of the femur) that fits into a socket in the pelvis to form the hip joint. Just below the head is a constriction, or neck, and two large processes - an upper, lateral "[|greater trochanter]" and a lower, medial "[|lesser trochanter]." These processes provide attachments for muscles of the legs and buttocks. Femoral condyles are large, rounded bumps on the distal end of the femur. They articulate with the condyles of the tibia and form part of the knee joint. The neck of the femur gives the hip joint a wide range of movement, but it is a point of weakness and a common site of fracture.

Parts of a Long Bone
A long bone, such as one in an arm or leg, has at its end an expanded portion called an "epiphysis," which articulates or forms a joint with another bone. On its outer surface, the articulating portion of the epiphysis is coated with a layer of hyaline cartilage called "articular cartilage." This layer is resistant to wear and produces a minimum of friction when it is compressed as the joint is moved. The shaft of the bone, which is located between the epiphyses, is called the "diasphysis." Except for the articular cartilage on its ends, the bone is completely enclosed by a tough, vascular covering of fibrous tissue called the [|periosteum]. This membrane is firmly attached to the bone, and its fibers are continuous with various ligaments and tendons that are connected to it. It also functions in the formation and repair of bone tissue. The wall of the disphysis is composed of tightly packed tissue called "compact bone." This type of bone is solid, strong, and resistant to bending. The epiphysis, on the other hand, are composed of largely "spongy" (cancellous) bone with thin layers of compact bone on their surfaces. Spongy bone provides strength and its bony plates are most highly developed in the regions of the epiphyses that are subjected to forces of compression. Both compact and spongy tissues are usually present in every bone. Compact bone in the diaphysis of a long bone forms a rigid tube with a hollow chamber called the "medullary cavity." The cavity is continuous with the spaces of the spongy bones. =Ischium= The "ramus" of the ischium is the thin, flattened part of the ischium (lowest part of the coxal bone), which ascends from the lower part of the body and joins the inferior ramus of the pubis - the junction being indicated in the adult by a raised line. The combined rami are sometimes called the "ischiopubic ramus." The [|ischium] is the posterior inferior compart of the pelvis. Posteriorly, bony prominences form the ischial tuberosity or each side of the inner pelvis and support the body's weight in a sitting position. The large opening called the obturator foramen is formed by both the rami of the ischium together with the pubis and creates the opening that allows for the passage of major blood vessels and nerves to the legs and feet. =Hip Diseases=
 * **[|Osteoarthritis]** mainly damages the joint cartilage, but there is often some inflammation as well. It usually affects only one or two major joints (usually in the legs). It does not affect the internal organs**.** The cause of hip osteoarthritis is not known. It is thought to be simply a process of [[image:http://upload.wikimedia.org/wikipedia/commons/thumb/9/93/Gonarthrose-Knorpelaufbrauch.jpg/190px-Gonarthrose-Knorpelaufbrauch.jpg width="190" height="175" align="left" caption="Osteoarthritis in the knee joint" link="http://en.wikipedia.org/wiki/Image:Gonarthrose-Knorpelaufbrauch.jpg"]]“wear and tear” in most cases. Some conditions may predispose the hip to osteoarthritis, for example, a previous fracture that involved the joint. Growth abnormalities of the hip (such as a shallow socket) may lead to premature arthritis. Some childhood hip problems later cause hip arthritis (for example, a type of childhood hip fracture known as a Slipped Epiphysis; also Legg-Perthe’s Disease). In osteoarthritis of the hip the cartilage cushion is either thinner than normal (leaving bare spots on the bone), or completely absent. Bare bone on the head of the femur grinding against the bone of the pelvic socket causes mechanical pain. Fragments of cartilage floating in the joint may cause inflammation in the joint lining, and this is a second source of pain. X-rays show the “joint space” to be narrowed and irregular in outline. There is no blood test for osteoarthritis.
 * **Rheumatoid Arthritis (R.A.)** starts in the synovium and is mainly “inflammatory”. The cause is not known. It eventually crushthe joint cartilage. Bone next to the cartilage is also damaged; it becomes very soft (frequently making the use of an uncemented implant impossible). R.A. affects multiple joints simultaneously. It also affects internal organs. Another form of hip arthritis that is mainly “inflammatory” is //Lupus//. There are other more rare forms of arthritis that are also mainly “inflammatory”. They are basically similar to R.A.. X-ray changes in R.A. are essentially similar to osteoarthritis plus a loss of bone density.
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Jeffrey L. Cameron M.