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Total knee replacement, or knee arthroplasty, is a surgical procedure in which the worn, damaged surfaces of the knee joint are replaced with metal and high-density plastic. Total knee replacement may result in general pain relief, deformity correction, and resumption of normal activity.
The knee joint is the largest in the body. It contains three different bones that join together to form the knee: thigh bone (femur), shin bone (tibia), and kneecap (patella). The bones are lined with a tough, elastic tissue (articular cartilage) that cushions the bones and keeps them from rubbing together. Tough bands of tissue (ligaments) attached to the femur and tibia provide stability. Long thigh muscles provide knee strength. The capsule-like tissue lining (synovial membrane) creates a lubricant (synovial fluid) that nourishes the cartilage, which lacks blood supply. The kneecap protects the joint and anchors the tendons, while stabilizing the joint with additional support from the muscles.
Over time, cartilage lining the ends of the bones wears away due to aging, disease, or trauma. When the bones rub together, deformities and extreme pain occur. As the bones wear, pieces of the bones (debris) are shed. The debris then irritates the lining of the knee. For a time, this irritation can be treated conservatively through medication, physical therapy, crutches, canes, walkers, or minor surgical procedures. When these treatments lose their effectiveness and the deformities or pain become severe, reconstructive surgery is the recommended treatment.
The most common reason for knee replacement surgery is gradual degeneration of bone and joints (osteoarthritis). Rheumatoid arthritis (inflammation of the tissue around the joints) is a second cause of knee deterioration. A third cause for knee replacement is post-traumatic arthritis, a form of arthritis caused by knee injury. The pain from post-traumatic arthritis sometimes manifests many years after the injury.
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Source: Medical Disability Advisor
| Pain relief from osteoarthritis and rheumatoid arthritis, injury to the knee, and restoration of knee function are the primary indications for total knee replacement. The decision to perform the procedure is not based on x-ray findings alone, which may, in fact, show extensive changes in the joint. The two main determining criteria are pain and loss of function.
Until recently, knee replacement implants (prostheses) were affixed to the individual's bones with bone cement and were expected to function for 10 to 15 years. Because of this time constraint, knee arthroplasty was often delayed until the individual was older. Technology has recently advanced to allow biological fixation of implants to the bone. The latest addition to this fixation process is the use of hydroxyapatite (a substance normally found in bone that promotes bone growth) in the prosthesis. Studies of cementless designs at 10 to 12 years show a 95% rate of prosthesis survival (Palmer).
The currently accepted standard for total knee replacement in the US is a cemented femur and cemented tibial component (Palmer). A cemented patella button is also placed.
Today, individuals are enjoying prostheses that may now be worn for more than 20 years without revision. |
Source: Medical Disability Advisor
| A total knee replacement is usually performed with the individual under general anesthesia, but the procedure can be performed under regional anesthesia. The choice of which to use is a complicated issue and can be affected by the individual’s comorbid medical conditions, if any. The choice of anesthesia is ultimately left up to the anesthesiologist with input from the surgeon. Postoperative care, especially pain control and prophylactic measures against blood clots (thrombosis), may differ following regional anesthesia (Crockarell).
As the procedure begins, the orthopedic surgeon makes a 6- to 12-inch incision over the affected knee. The kneecap (patella) is removed. The adjoining surfaces of the femur and tibia are shaved to eliminate any rough edges and to permit better adhesion of the prosthesis. Prosthetic kneecaps are now specially designed for both men and women to account for differences in anatomy. Whether these will function better or last longer for individuals is not yet known. One metal part of the prosthesis attaches to the bottom of the femur; a smaller, high-density plastic part attaches to the top of the tibia with a rod-like part that inserts into the shaft of the bone. A high-density plastic "tray" on top of the metal rod provides a resting place for the metal cap and the end of the femur and acts as cartilage for the new joint. The new joint is anchored into place with bone cement or a biological fixation process.
The individual returns from what is usually a 2-hour surgery with a large dressing to the knee area, several IV lines in place, and wearing anti-embolism or pneumatic stockings. A small drainage tube positioned during surgery helps drain excess fluids from the knee joint. The individual's leg may be placed into a mechanical device that bends (flexes) and straightens (extends) the knee at a pre-set rate and amount of flexion (continuous passive motion, or CPM device). Gradually, the rate and amount of flexion is increased as tolerated by the individual. Some orthopedists recommend that the leg be in the CPM device when the individual is in bed, although not all surgeons will use the CPM following knee replacement. Multiple studies have shown CPM to assist in obtaining knee flexion more quickly, which may shorten hospital stays (Crockarell). Other postoperative techniques to speed recovery include encouraging passive knee extension by placing the individual’s foot on a pillow while in bed or promoting flexion by dangling the legs over the side of the bed (Crockarell).
The IV lines in place after surgery provide hydration and nutrition. They will remain in place until the individual is ingesting adequate amounts of liquids orally. Preventive (prophylactic) antibiotics may be given to reduce the risk of developing an infection (a development that could necessitate the removal of the artificial knee).
The anti-embolism stockings reduce the individual's risk of developing blood clots (emboli), which are more common after lower extremity surgery. Other measures (such as moving about, walking and bending, and straightening the ankles) are encouraged to prevent the development of blood clots. Individuals are instructed in a home exercise program for postoperative recovery. Many surgeons suggest that individuals receive this instruction from physical therapists prior to surgery so that postoperative pain and the use of painkillers (analgesics) do not interfere with the individual’s understanding of the exercise routine. |
Source: Medical Disability Advisor
| The short-term outlook for total knee replacement is excellent. Most individuals can stand the morning after surgery and begin to exercise that day. With the support of walkers or crutches, individuals can walk with confidence, climb stairs, and ride in a car by the time they leave the hospital. Physical therapists can instruct the individual in motion exercises that are the key to a good result; these activities should continue for several months. Some swelling, aching, and numbing are normal during this time. Most individuals are able to return to their normal activities within 6 weeks after surgery.
The long-term outlook after total knee replacement is also very good. One group of findings suggests that individuals with well-performed knee replacements can expect a 91% to 96% chance that their knee replacement will be in place and functioning at 14 to 15 years (Palmer). Individuals can influence these odds by maintaining an ideal weight, exercising, protecting against infection, and avoiding impact sports. |
Source: Medical Disability Advisor
| Note on research and authorship Ideally, rehabilitation begins before total knee replacement surgery by assessing the individual's medical and social condition to determine what might be required postoperatively for a successful outcome. The main goal of the rehabilitation is to restore function by controlling pain, improving range of motion, and strengthening the knee (Ranawat).
Individuals who undergo total knee replacement require both physical and occupational therapy. Occupational therapy is needed after surgery for instruction in all transfer training, equipment needs, and activities of daily living modifications. The occupational therapist should assess and train individuals in use of equipment such as an elevated commode, tub seat, reacher, long-handled shoe horn, and long-handled sponges, because these facilitate activities of daily living in the postoperative period.
Physical therapy begins in the hospital and continues on an outpatient basis. The first goal of physical therapy is to control of pain, initiate ambulation and begin range of motion of the operative knee. Preoperative gait instruction might facilitate early postoperative ambulation. Weight bearing status is determined by the physician's protocol, and individuals may use assistive devices as needed for independent ambulation on level and uneven surfaces. Cold packs may be used to decrease pain and swelling, with care used to protect the surgical wound.
The second goal of physical therapy emphasizes full knee range of motion. Range of motion restrictions are determined by the surgical approach and type of prosthesis to protect the prosthesis and surrounding soft tissue. Common clinical practice includes use of continuous passive motion machines combined with physical therapy to facilitate recovery and knee motion (Milne).
Physical therapy's final goal is to increase knee and hip strength, normalize gait, and increase functional abilities. Because many individuals experience an abnormal (antalgic) gait or limb weakness preoperatively, continued gait training and strengthening exercises may take longer than anticipated. All weight bearing and exercise should be continued under the direct guidance of the surgeon to protect the integrity of the knee prosthesis. Besides undergoing supervised rehabilitation, the individual should be instructed in a home exercise program to be practiced daily, and continued independently under physician supervision after the completion of rehabilitation (Fitzgerald; Roos). |
| FREQUENCY OF REHABILITATION VISITS | | Surgical | |
| Physical or Occupational Therapist | | Up to 24 visits within 12 weeks | |
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| The table above represents a range of the usual acceptable number of visits for uncomplicated cases. It provides a framework based on the duration of tissue healing time and standard clinical practice. |
Source: Medical Disability Advisor
| Although blood clots of the leg veins (thrombophlebitis) are not rare, death from this malady has been almost totally eliminated with use of support stockings, knee motion machines, and blood thinning medications (such as low-dose warfarin, low molecular weight heparin, and aspirin). Risk factors for developing thrombophlebitis include a previous history of thromboembolism, heart attack (myocardial infarction), prolonged immobility, and estrogen use. Individuals without a previous history of thromboembolism may receive drugs to guard against blood clots (chemical prophylaxis) for up to 2 weeks after surgery. Individuals with a history of thromboembolism may receive chemical prophylaxis for up to 6 weeks after surgery (Crockarell).
Blood clots of the leg arteries (arterial thrombosis) occur in only 0.03% to 0.17% of cases but are devastating and can lead to amputation. They are more likely to occur in individuals with significant vascular disease; those individuals should seek a vascular surgery consultation prior to knee replacement (Palmer). Methods of detecting postoperative blood clots include x-ray (venography) with contrast media, and duplex ultrasound.
Infection in a total knee replacement is relatively rare but can be disastrous. Its incidence ranges from 2.6% to 1.6% of cases, depending on the study consulted (Crockarell). Symptoms of infection include swelling (edema), redness (erythema), tenderness, and painful range of motion. Sudden (acute) onset of pain in a previously pain-free and well-functioning knee replacement may also accompany the onset of infection (Crockarell).
Like other complications, an infection is better avoided than treated. In increasing numbers of hospitals, all joint replacement surgery is performed in special laminar flow operating rooms designed to keep out dust, germs, and unclean air. The surgeons also wear full-body "space suits." These full-body suits, worn over normal scrubs, allow the surgeons to move and breathe without spreading germs, because an exhaust tube carries contaminated, dirty air out of the room. An infection rate of less than 0.5% in joint replacement surgeries is achievable in some hospitals. With proactive use of deterrents, such as preventive (prophylactic) antibiotics, ultraviolet light, and meticulous and expeditious surgery, the overall occurrence of postoperative infections is 1% (Palmer).
Formation of obstructive scar tissue (arthrofibrosis) follows surgery in approximately 1% of cases (Palmer). Initially treated with conservative measures, such as anti-inflammatory medication and physical therapy, it can also be treated more aggressively with continuous passive motion (CPM), and follow-up (revision) surgery.
Other long-term complications, such as wear, stiffness, or loosening of prosthetic parts, relate as much to the individual's behavior as to surgical success. However, knees with prosthetic-part problems can usually be improved through revision surgery. |
Source: Medical Disability Advisor
| Sedentary work and light work can be performed sooner if done sitting. Work restrictions include limited use of the knee, including avoidance of kneeling, squatting, twisting, jumping, climbing, prolonged standing, and walking. In general, heavy and very heavy work is not appropriate after total knee replacement. Prolonged sitting is also to be avoided because of potential for increased swelling of the lower extremity. Restrictions may become permanent.
Work accommodations include use of assistive devices for ambulation, frequent rest periods, and avoidance of at-risk activities. Accommodations are conducive to a more rapid return to full-time work.
Use of prescribed medications will require review of drug policies. Work release time for rehabilitation will be required. |
Source: Medical Disability Advisor
| Crockarell, John R., and James L. Guyton. "Arthroplasty of the Knee." Campbell's Operative Orthopaedics. Eds. S. Terry Canale and James H. Beatty. 11th ed. Philadelphia: Mosby Elsevier, 2008. Fitzgerald, J. D., et al. "Patient Quality of Life During the 12 Months Following Joint Replacement." Arthritis and Rheumatism 51 1 (2004): 100-109. National Center for Biotechnology Information. National Library of Medicine. 4 Oct. 2008 <PMID: 14872462>. Milne, S., et al. National Center for Biotechnology Information. National Library of Medicine. 4 Oct. 2008 <PMID: 12804511>. Palmer, Simon H., and Mervyn J. Cross. "Total Knee Arthroplasty." eMedicine. Eds. T. M. DeBerardino, et al. 30 Jan. 2004. Medscape. 18 Feb. 2009 <http://www.emedicine.com/orthoped/topic347.htm>.>. Ranawat, C. S., A. S. Ranawat, and A. Mehta. "Total Knee Arthroplasty Rehabilitation Protocol: What Makes the Difference?" Journal of Arthroplasty 18 3 Suppl 1 (2003): 27-30. National Center for Biotechnology Information. National Library of Medicine. 4 Oct. 2008 <PMID: 12730924>. Roos, E. M. "Effectiveness and Practice Variation of Rehabilitation after Joint Replacement." Current Opinion in Rheumatology 15 2 (2003): 160-162. National Center for Biotechnology Information. National Library of Medicine. 4 Oct. 2008 <PMID: 12598806>. |
Source: Medical Disability Advisor
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