To help you understand what medical staff may be talking about, here’s a “Hip and Knee Glossary of Terms” guide to some common words used in treating patients with hip and knee arthritis or joint issues.
Refers to one of the internal knee ligaments, called the anterior cruciate ligament.
The socket, cup-shaped part of the pelvis into which the ball-shaped head of the femur fits. The hip joint is a ball-and-socket joint; the acetabulum is the socket. During a hip replacement, the worn out bone and cartilage in the acetabulum is removed, the socket is reshaped, and a properly-sized prosthetic socket is inserted to rebuild the patient’s own worn out socket.
A type of graft tissue, whether bone or ligament/tendon, that is taken from a deceased person who donated their tissue, then implanted in another patient who has a tissue deficiency. Allergic responses to foreign tissue are prevented by processing the tissue so that the proteins are removed. Thus, for example, bone allografts do not have proteins, just the calcium and supporting structure that can be very helpful in rebuilding bone loss in complex hip and knee replacements. Allografts are usually used only in very complex, re-do hip and knee replacements, and almost never used in a first-time surgery situation.
A ceramic material used in orthopaedic (usually total hip) bearings. The wear rate of alumina ceramic bearings is better than anything other material. When people refer to ceramics in joint replacement surgery, they usually mean alumina, since alumina and its composites are the only ceramic used presently in hip replacement surgery. Alumina ceramics are used in knee replacements also, but not in the U.S. as yet. While there is a theoretical risk of an alumina bearing breaking in the body, this risk is extremely small.
This term refers to pain killing or reducing medications used by doctors. The analgesic class of drugs includes common names like aspirin and Tylenol (acetaminophen), as well as narcotic pain relievers like morphine, Vicodin, and others.
The “anterior approach” is a term used by surgeons who do hip replacement surgery. It refers to the anatomic pathway the surgeon must take to reach the hip joint. Patient recovery is generally better with this surgical approach, at least in our experience. One key advantage of this surgical method is that is muscle-sparing.
Surgical procedure to alter a joint, relieve pain, and restore range of motion by realigning, reconstructing, or replacing a joint. This term also refers to partial or complete excision of a diseased joint. Typically, when surgeons refer to a total hip or knee arthroplasty they are referring to a total hip or knee replacement procedure.
An outpatient diagnostic and treatment procedure using a lighted optic tube which is inserted into the joint through a small incision. Images of the inside of the joint are projected onto a screen. Small instruments inserted through the incision into the skin are used to perform the surgery. Arthroscopy minimizes surgical trauma with essentially no blood loss. Arthroscopic procedures are most commonly performed in the knee, shoulder, and hip joints.
A type of graft tissue taken from the same patient, but from another location. Typically, bone is removed from the pelvis and put in complex fractures, or other operations to promote healing. In hip and knee replacement surgery, we almost never need these types of grafts. Most grafts in joint replacement surgery are of the “allograft” type, and even those are rarely needed.
Loss of bone caused by insufficient blood supply. Loss of blood supply can occur for many reasons such as steroid or heavy alcohol use and exposure to certain chemicals. In many cases, the cause of avascular necrosis is unknown. In the hip joint, it leads to progressive collapse of the femoral head (the ball of the hip joint), and secondary arthritic changes. In the knee, avascular necrosis is less common.
Fluid-filled sac located between a bone and a tendon or muscle. Bursa sacs are normal and allow smooth gliding of the tendons and ligaments during normal movement of the joints. In disease processes such as arthritis, the bursa sacs located close to the joint may become inflamed and painful. In hip bursitis, for example, cortisone injections can help, and outpatient arthroscopic surgery is very effective in relieving pain.
Smooth tissue that lines a joint to cushion the bone and allow the joint to move easily without pain. Cartilage is the body’s natural bearing surface, with very low friction and a soft, pliable, wet surface that is like a shock absorber. Once destroyed by arthritis, cartilage cannot grow back or repair itself. Cartilage replacement is still investigational, and successful only in young athletes with isolated, small cartilage lesions. Diffuse wear and tear of cartilage requires joint replacement surgery, and that is the state of the art treatment today.
Superficial reddening and inflammation of the skin, which is accompanied by local pain. Cellulitis can occur with or without surgery, and is typically related to a staph bacterial infection. While redness can be caused by other, more benign reasons, such as local pressure, and swelling, the word cellulitis is used in relation to an infection, usually in the early stages. In joint replacement surgery, cellulitis can occur around the incision, and, if treated promptly with antibiotics and warm packs, it should resolve within 24-48 hours.
Potent anti-inflammatory hormones that are made naturally in the body or synthetically for use as drugs. The most commonly prescribed drug of this type is prednisone. Smaller doses of steroids are used in joint injections to relieve pain by reducing inflammation. Many patients benefit from such injections and can postpone surgery for a long time.
Anticoagulant used to prevent the formation of blood clots. The generic name for Coumadin is warfarin. This drug thins the blood and decreases the risk of blood clots after surgery. Today, there are newer drugs to replace Coumadin. Some studies have shown that even twice-daily aspirin is effective in reducing clot formation after surgery.
There are two cruciate ligaments in the knee (so-called since they cross each other in the middle of the knee). These ligaments are about the thickness of the little finger. They keep the knee joint from moving too far forward or backward; in other words, they keep the tibia bone from slipping out from under the femur bone when the knee goes through a range of motion. During most total knee replacements, both cruciate ligaments are surgically removed, in some designs the PCL or posterior cruciate ligament is preserved. Both cruciate ligaments are preserved entirely in partial (uni-compartmental) knee replacements.
Deep Venous Thrombosis (DVT):
Also known as a blood clot. After hip or knee surgery, or any surgical procedure, the risk of blood clots increases. Obesity, diabetes, certain genetic profiles, inactivity, trauma, burns, and orthopaedic procedures increase the risk of DVT. A previous history of DVT and family history of clots can increase the subsequent risk of clot formation. Compression boots, early exercise and ambulation, minimizing the surgical trauma, and anticoagulant drugs reduce DVT risk.
DVTs can pose a risk if the clot breaks off and lodges in the lung, causing breathing difficulty, chest pain, and even death. This is very rare. New and unexpected swelling of the leg, calf pain, cough, chest pain, or difficulty breathing after surgery can be indicative of a blood clot. Leg ultrasound and CT scans can help diagnose DVT and lung clots. If a leg clot is found, blood-thinning medication must be continued for a longer duration, such as six months after surgery. By that time, the body re-absorbs the clot on its own. The medication ensures that the DVT does not grow further in size.
Also known as DLC, and mostly of research interest at present. DLC coatings are being investigated as super-tough materials that can decrease bearing wear dramatically in hip and knee replacements. Some such research has found its way into clinical application, but most DLC materials are still investigational.
Movement in which the bones on either side of the joint are taken farther apart, increasing the angle of the bones. Extension is the opposite of flexion. When you straighten your knee, you are extending the knee joint. In the hip, extension refers to the ability to swing the thigh back, such as when you take a step back.
Your ability to stand and walk depends on being able to straighten the knee out fully after surgery. With progressive arthritic change in the knee joint, people lose the ability to fully straighten the knee. Knee replacement will restore extension, the ability to straighten out the knee.
This is the ball part of the hip joint. The hip is a ball-and-socket joint. The femoral head sits at the top end of the femur, which is the thigh bone, and the largest bone in the body. The femoral head is covered with a smooth layer of cartilage. During walking, this head, or ball moves back and forth inside the socket. The femoral head is removed entirely during a total hip replacement.
The longest and largest bone in the human body, connecting the hip joint to the knee joint. One end of the femur is the hip joint, and the other end is the knee joint.
Movement in which the bones on either side of the joint are brought closer together, decreasing the angle of the bones. Flexion is the opposite of extension. When you bend the knee, you are flexing the knee, in medical terms.
Pattern of how a person walks. With hip and knee arthritis, the gait pattern is altered, leading to a limp. Typically, the patient will subconsciously put less weight on the arthritic joint, leading to an abnormal gait, and a noticeable limp.
An alternative to total hip replacement, this operation is similar in that the hip joint is replaced with artificial parts. But, instead of replacing the femoral head, it is preserved, and capped (resurfaced) with metal. There is very little advantage to hip resurfacing over hip replacement. Hip resurfacing, which had been around for many decades, has now fallen out of favor because of concerns about metal-on-metal bearings. Until the bearing surfaces for hip resurfacing improve, patients should avoid having hip resurfacing.
The moving connection between two bones or elements of a skeleton. The knee, for example, is the joint of the femur and the tibia. Likewise, the hip is the mobile point between the pelvis and the femur bone. Joints are covered on the inside by smooth cartilage and have a small amount of natural lubricating fluid. Diseased and worn joints feel less pain when cortisone injections are given to reduce the inflammation in the joint. Anti-inflammatory medications such as ibuprofen work the same way, relieving pain by reducing inflammation. Also see ligaments.
This is a technical term describing one of several available anatomic pathways that the surgeon can take during hip replacement surgery. This particular method reduces the risk of hip dislocation, but has the disadvantage of a limp for about a year after surgery. We do not use this approach in our practice for first-time hip replacement, preferring the anterior approach instead, which is a true muscle-sparing method.
Legg-Calve’-Perthes disease (also called Perthes disease):
A hip disorder that develops in childhood. The theory is that during childhood, for some unknown reason, the blood supply to the hip ball (femoral head) is lost. As a result, a part or all of the bone involved temporarily dies. The socket part of the hip (acetabulum) is fine, but the head intermittently loses its blood supply and goes through cycles of healing and injury. As a result, the head becomes deformed.
Instead of the usual round shape of the hip ball, a patient with Perthes disease has a flattened and deformed hip ball on X-rays. Because of the incongruence between the flat head and the round socket, degeneration and arthritis can set in. These patients are typically referred for joint replacement surgery and the challenge is how to defer surgery as long as possible, since many patients with Perthes disease will develop hip arthritis early on in their lives. After hip replacement, of course, the pain is relieved, and function and movement are restored.
Joints are held together by ligaments. With advanced arthritis, these ligaments can become torn and stretched. During a hip or knee replacement procedure, the supporting ligaments are preserved, and adjusted by the surgeon to get as much mobility and stability back as possible. If necessary, special implants can be used that substitute for the damaged ligaments and provide stability to the joint.
Anticoagulant used to prevent the formation of blood clots. This is a substitute for Coumadin. The disadvantage of using Lovenox over Coumadin is higher cost and the need for the daily injections that the patient must self -administer. The advantage is that routine monitoring of the drug’s affect is not necessary.
The complex system involving the body’s muscles and skeleton – including the joints, ligaments, tendons, and nerves. This system holds us up and allows us to walk and run. The hip and knee joints are part of the musculoskeletal system. Certain diseases such as ankylosing spondylitis, rheumatoid arthritis, lupus, fibromyalgia, psoriasis, and osteoarthritis have profound effects of the musculoskeletal system. Ultimately, these diseases may lead to the destruction of major joints such as the hip and knee joints, necessitating reconstructive surgery on these joints.
Abbreviation for the class of nonsteroidal anti-inflammatory drugs. NSAIDs do not contain corticosteroids and are used to reduce pain and inflammation. Aspirin and ibuprofen are the two commonly used NSAIDs. These drugs are the first line treatment for arthritic pain. They reduce pain by interrupting the cycle of inflammation that causes pain in diseased joints. NSAIDs do not alter the course of degenerative arthritis, and none of them restore cartilage. Celebrex is among the newest in this class of drugs with fewer gastrointestinal side effects. Previous NSAIDs such as Naproxen, Relafen, Feldene and others may be equally effective for some patients. The pain and stiffness of early osteoarthritis will respond very remarkably to Tylenol (acetaminophen) or one of the NSAID drugs. It is wise to try such medications before thinking about surgery since these drugs are safe over the long-term, and can work very well for some patients.
Also known as degenerative joint disease. Cartilage that cushions the ends of bones breaks down causing bones to rub together. The patient may experience pain and loss of movement. With physical breakdown of the joint space, the shape of the joint surfaces is altered, and the friction inside the joint increases. The diseased joint may feel hot and swollen. Symptoms will respond to Tylenol, appropriate exercise, hydration, and NSAIDs. If X-rays show destruction of the joint, and if all other means of controlling pain have failed, and if the joint begins to lose mobility, replacement of the osteoarthritic joint with artificial implants should be considered. Additional information is available through The Arthritis Foundation.
Refers to realignment of the arthritic joint. This is a procedure that is not as common as hip or knee replacement surgery. As an example, a relatively young patient with knee arthritis localized to the inside of the knee joint and a leg that is bow-legged for some reason, may be a candidate for an osteotomy of the tibia. The surgeon will cut the tibia bone close to the joint, and realign the leg, so that the patient’s weight and loadbearing are altered and less painful. As joint replacement surgery has become more advanced and successful, the role of osteotomy in managing arthritis has become less prominent.
Partial knee replacement:
Same as Uni-compartmental knee replacement.
Perthes Disease: Same as Legg-Calve’-Perthes disease.
Refers to one of the internal knee ligaments, called the posterior cruciate ligament. Also see ACL in this glossary. In most knee replacement surgery, the PCL is preserved and works with the knee implants to help stabilize the joint.
Primary care physician:
A general practitioner who provides preventive care, identifies and treats common medical conditions, and makes referrals to medical specialists when necessary. Some insurance companies require patients to have a primary care physician refer them to an orthopaedic surgeon. While we may instinctively seek a specialist for our ailments in the U.S., the value of a good primary care physician cannot be overemphasized.
A primary care doctor can diagnose your problem, get appropriate X-rays, and initiate therapy, pain management, and lifestyle alterations that can keep you going and help you avoid surgery. The primary care doctor has the big picture in mind.
In contrast, a specialist, such as an orthopaedic surgeon, particularly one who is focused on reconstruction of the hip and knee joints, has a much more focused and limited view. It is worthwhile to have a good primary care doctor to learn about preventative care, maintain good health, and, when necessary, get referred to a specialist.
An artificial body part replacement. For hip and knee replacement procedures, the prosthesis refers to the set of artificial components, usually consisting of metal and plastic, that will be used to replace the arthritic joint.
Range of motion (ROM):
Measurement of the arc of movement of joints such as the hip or knee. ROM can help the patient, and the physical therapist, measure progress after joint replacement surgery. In addition to flexion and extension, hip and knee joints also rotate internally and externally. The combination of flexion, extension, internal rotation, and external rotation determine the range of motion of the hip and knee joints. The hip can also be kicked away from the body in a lateral movement called abduction, or it can be swung in toward the opposite leg laterally in a movement called adduction. These movements are not present in the knee, since the knee has to be stable against side-to-side movement during walking.
A chronic inflammatory disease that causes joint pain, stiffness, and swelling. A systemic problem, the disease affects the entire body, including the musculoskeletal system. It can lead to severe destruction of the hip and knee joints, requiring joint replacement surgery.
Silicon nitride ceramic:
A relatively new type of ceramic material made by a company called CTL Amedica and already in use in certain spinal operations. The toughness and strength of this ceramic is superior to the other ceramic materials available to orthopaedic surgeons today. The wear properties of this new type of ceramic are excellent.
Ligaments, tendons and muscles in the musculoskeletal system. These are critical components of your major joints, but you cannot see them on the X-rays, which show only bones. The condition of your soft tissues will have a major impact on your recovery and ultimate result from joint replacement surgery. A program of regular, low-impact exercise is the best option to keep the soft tissues in good condition. MRI scans can show soft tissue, while CT scans are better for bone imaging.
A partial or complete tear of a ligament.
A partial or complete tear of a muscle or tendon.
Inflammation of the synovial membrane, the tissue that lines and protects the joint. Synovitis occurs almost inevitably in arthritic hip and knee joints and contributes to that swelling and stiffness that goes along with arthritis.
A clear, sticky fluid that is released by the synovial membrane and acts as a lubricant for joints and tendons. This is the equivalent of the body’s natural grease, or WD-40. Synovial fluid is recycled by the body, just like an oil change in a car. Progressive arthritis and wear of the hip and knee ultimately overwhelm the body’s capacity to provide a smooth gliding surface for the joints.
The biological lining of the major joints in the human body, such as the hip and the knee. The lining produces synovial fluid.
The tough cords of tissue that connect muscles to bones. Tendons are the motors that drive the joint in one direction or another. Just above and below your kneecap is a tough, rope-like structure that consists of a tendon. This tendon, called the quadriceps tendon, is what produces the ability to straighten the knee from a bent position. If this tendon were completely torn, the knee would dangle, and you would not be able to straighten it out, no matter how hard your muscles tried. It would be like breaking the drive shaft of a car. You can rev the engine all you want, but the wheels would not spin. Tendons take the power of the muscles and convert it to useful movement of the joints.
An inflammation in a tendon or the tendon covering, commonly treated by primary care physicians. Tendonitis typically responds quickly to NSAID drugs, rest, and appropriate rehabilitation.
Shin bone or larger bone of the lower leg. If you run your hand down the front of the leg, from the knee to the front of the ankle, the hard bony surface is the front of the tibia bone. The tibia connects the knee joint to the ankle joint.
Uni-compartmental knee replacement:
This refers to a partial knee replacement, which resurfaces either the inside or outside of the knee. The surgery is less extensive and recovery is faster. If arthritis progresses in the un-replaced parts of the knee joint later on, then conversion to a total knee replacement can be done. Very few people are candidates for a partial replacement; a total knee replacement is the better option for most patients with osteoarthritis.
This was a shim-like device that could be inserted between arthritic surfaces of a knee joint. As it stands now, while the concept is simple enough, it simply does not work to relieve pain. At present, this device is no longer marketed in the United States.
: A newer anti-coagulation drug, taken once a day, to thin blood after joint replacement surgery. Usually taken for a month after surgery, this drug does not require monitoring, unlike the case with Coumadin.
This type of tissue is taken from an animal (i.e., a different species than humans) and processed before implanted in the body. An example is heart valves from pigs that are used to repair or replace defective heart valves in humans. In hip and knee replacement surgery, we usually do not use xenograft tissue. Most large bone, tendon, or ligament defects in joint replacement surgery are repaired by allograft tissue instead.
A type of ceramic material that has been used in the past for both hip and knee prosthesis bearings. This material is stronger than alumina ceramic (which is the more common ceramic used today in artificial joint replacements), but zirconia can behave very erratically in the body and is very sensitive to even small changes in manufacturing variables. Accordingly, this material is no longer available for hip and knee bearing in the United States. Instead, a composite of two ceramics, alumina and zirconia is used at the present time in hip and knee replacement bearings.