Hip Resurfacing

Most knee diseases are diagnosed with a thorough history, a straightforward physical examination, and routine x-rays (radiographs). Blood tests and additional imaging tests are often not required for most diagnoses. However, MRI is particularly helpful for examining the soft tissues (e.g., ligaments and menisci) in the knee, and for this reason MRI is more commonly used for diagnosing knee problems than it is for hip problems History and Physical Examination As with most joint problems, an orthopaedic surgeon will typically ask questions about the involved joint, activity levels, and symptoms. In most offices, an initial intake questionnaire usually covers most of the basic questions and medical history. The surgeon usually looks this over first, and x-rays may be ordered before or after examining the patient. Nearly all patients having hip or knee surgery will have an x-ray beforehand. X-rays (also known as radiographs) are also usually obtained before an MRI is ordered. The history is often the most informative part of the interview, and most surgeons have a fairly good idea of the diagnosis (or a short list of possible diagnoses) based on the history before even examining the knee or obtaining any x-rays. Surgeons usually ask about the location, severity, and frequency of the pain, along with what sorts of things bring it on and what makes it better. Specific questions with knee problems may deal with previous history, particularly if there has been any prior surgery or accidents, or with narrowing down specific complaints. It is important to know if the knee is experiencing mechanical problems in addition to the pain, such as buckling, catching, or locking. A history of redness or rash may suggest an infectious problem, such as Lyme disease. All of these details are important. The physical examination usually focuses on the affected joints themselves and adjacent joints, checking range of motion and function. Neurologic and vascular function are usually noted. Peripheral vascular disease can cause leg pain (known as claudication) and also can present problems for surgery. There are many provocative tests and maneuvers used during a physical examination to further narrow down the particular source of the problem. Pain along the joint line is often indicative of arthritis and meniscal tears. Do not be surprised if your surgeon watches how you walk in and out of the office. As with hip problems, gait abnormalities are often very suggestive of the problem. It is important to note that many patients who present with knee pain may actually have referred pain from the hip. Although the knee may be where the pain seems to be focused, these patients often have stiffness around the hip (particularly with rotating the hip joint, as with putting on shoes or socks) and a limp that is suggestive of hip problems. I see patients every month who arrive reporting both severe knee pain and that they have been told that their knee x-rays are fine; it sometimes turns out that these patients actually have severe hip arthritis when we get an x-ray, and they usually find that the knee pain goes away after treatment of the hip problem. Radiographs (X-rays) Plain x-rays of the knees are usually taken to evaluate for arthritis, fractures, congenital anomalies (such as excessive bowing or a shallow groove for the patella), tumors or metastatic disease, and other conditions. There are many things that the surgeon will be evaluating, often focusing on the appearance of the joint itself. The cartilage that coats the surfaces of the joints is transparent on the x-ray, but if the gap is not apparent, “bone-on-bone” arthritis can be seen. The gap typically is in the range of an eighth to a quarter inch, representing a cartilage layer between the bones, but it may be narrowed or even obliterated on one or both sides of the knee with severe arthritis. Other features of arthritic joints include subchondral sclerosis (hardening of the underlying bone), osteophytes (spurs), loose bodies, and cysts in the bone. For most knee problems, it is important that weightbearing knee films be obtained. These frequently need to be repeated if a patient arrives with nonweightbearing knee films and arthritis is a potential diagnosis. There are also specific views of the knee (such as flexed 30 degrees or a “sunrise” view of the patella taken with the knee flexed to evaluate the undersurface and tilt of the patella). Magnetic Resonance Imaging (MRI) MRI may sometimes be ordered to evaluate for soft tissue problems (such as muscle injury, ligament injury, meniscal tear, evaluation of soft tissue mass, etc.) or for bone marrow problems. It often will “light up” for increased water content, signaling edema and injury. Bone bruises and stress fractures show up in this manner. Avascular necrosis (osteonecrosis) is often diagnosed on MRI much earlier than when it appears evident on regular x-rays. A “torn cartilage” usually refers to a meniscal tear. The three dimensional cross sections show most (although not all) meniscal tears. These come in a variety of shapes and patterns. Anterior cruciate ligament tears and other ligament injuries also are often confirmed with an MRI. Although MRI is often very good at imaging problems within the knee, it is not perfect. Sometimes an MRI arthrogram is required to see it well. This involves injecting the knee joint with a contrast dye in order to see tears more clearly. This is most often used if there has been a prior surgery within the knee. Computed Tomography (CT) A computed tomography (CT) scan uses many xray “slices” to examine cross sections of a body or limb. The patient lays on a table while moving through a ring that contains a spinning x-ray camera. While it does have applications in trauma and spine surgery (especially when examining complex pelvic fractures), CT scans are not typically used to evaluate for arthritis. CT scans are most often used in the knee when evaluating complex fractures and trauma, such as a tibial plateau fracture (a severe fracture involving the joint surface of the tibia). Multiple small fragments and complex fracture patterns with a shattered knee can be seen on the many cross-sectional images and 3D reconstructions, aiding the surgeon in preoperative planning for surgical repair of these traumas. Nuclear Bone (Technecium) Scans Bone scans involve administering a very small amount of radioactive material via IV, then using a camera to view how it is taken up and eliminated by the tissues. Areas with high uptake, such as a tumor, infection, or fracture, will often “light up.” This test is also useful for determining if an old hip or knee replacement is loosened from the bone, although it will provide a false positive if a bone scan is obtained within about 1 year or less of the surgery. White Blood Cell (WBC) Scans A tagged white blood cell scan is a similar test to a bone scan, except white blood cells are taken from the body and “tagged” with a tiny amount of radioactive material. It is then re-injected, and the scanner shows where all of those tagged white blood cells congregate in order to localize an infection. This is used when trying to find an infection in the bone or around an artificial joint. Ultrasound An ultrasound examination uses sonic waves to make a picture of soft tissues. While it may be used to examine cysts or other soft tissue abnormalities (such as checking to see if an Achilles tendon is ruptured), its most common application in orthopaedics is to detect the presence of blood clots in deep veins. It is sometimes used to check the soft tissues around the knee for cysts, tumors, fluid collections, or aneurysms. Knee Aspiration (Arthrocentesis) Sometimes it is useful to draw joint fluid out of the joint with a needle for laboratory analysis. This is most common in situations where there has been or there is suspicion for an infection in the joint itself. Usually the skin is anesthetized with a local anesthetic and the needle is placed into the joint. Unlike hip aspiration, this typically does not require x-ray to perform. The aspirated fluid is sent to the laboratory for analysis to see if there is any evidence of bacteria or infection. Knee fluid is also often checked for crystals, which can be indicative of crystalline diseases such as gout or pseudogout (calcium pyrophosphate crystals). Please remember the information on this site is for educational purposes only and should not be used to make a decision on a condition or a procedure. All decisions should be made in conjunction with your surgeon and your primary care provider.