Fifty years ago, diseased knees relegated individuals to limited mobility, chronic pain and a greatly reduced quality of life, but thanks to incredible advances in medicine and particularly in orthopedic surgery, diseased knees need no longer circumscribe a person’s life.
Sometimes, when the inevitable path to increased disability is apparent, an orthopedic surgeon may suggest that you have this surgery sooner than later for a variety of reasons. Don’t wait until you are knee deep in trouble to seek advice. Do it today!
Knee replacement surgery (total knee arthroplasty) has finally come into its own and is now safe, effective and widely available. Not only that, but today’s artificial knees are so much more than the crude hinges of the past. The new designer knees are replacement joints made of a variety of materials like metal alloys, high-grade plastics and polymers and are individualized according to the age, weight, activity level and overall health of the recipient. Tailored made, no less! And, as reported by MSNBC, researchers have determined that knee replacement surgery, though expensive, is “worth the cost, especially if performed by experienced orthopedic surgeons.”
How common are knee replacements, you might ask? MSNBC states: “Some $11 billion is spent on 500,000 total knee replacements each year in the United States, and the number is projected to multiply seven times by 2030 because of the aging, overweight population.”
Indications for Knee Replacement
As mentioned above, the aging population will multiply the future need for knee replacement surgery seven fold. This is because the longer people live, the more likely they are to manifest osteoarthritis or some form of degenerative joint disease in one or more joints. However, this is not to say that joints wear out because of use. The wear-and-tear theory has been refuted on a number of fronts. But age and genetics do play a large part in the deterioration of the cartilage that lines the knee joint, which in turn causes osteoarthritis, the most common reason for knee replacement.
According to Dr. Robert Shmerling in a report for Harvard Health Publications, “an estimated 21 million people in the United States alone have osteoarthritis. If you’re fortunate enough to live to age 75 or older, chances are perhaps as high as 70% to 90% that you’ll have osteoarthritis in at least some joints.”
If you become part of this statistic, you will find yourself dealing with chronic pain, limited mobility, and as a result, a decreased quality of life. Not a pretty picture. Even though the preponderance of those needing knee replacements tends to be older people, young people can be likewise side-lined by osteoarthritis if joint cartilage is damaged by unusual or extreme joint stress as in some sports injuries.
The most common risk factors (not causes) for osteoarthritis include:
- Advanced age
- Obesity
- Family history - up to 50% of osteoarthritis is thought to be related to an inherited tendency to develop joint degeneration
- Injury - especially a fracture that involves the joint
- Rheumatoid arthritis (or other diseases that cause chronic joint inflammation)
Anatomy of the Knee
To understand what occurs during knee replacement surgery, it is helpful to have some understanding of the anatomy of the knee, a rather remarkable hinge joint with a slight rotational action. The bones of the knee are the femur (the large thigh bone), the tibia (the lower leg bone) and the knee cap or the patella that rides over the front of the joint where the other two bones meet. These three bones provide the rigid structure of the joint.
The bones are attached to the knee by two muscles that move the joint, the quadriceps in the front and the hamstring muscle in the back.
Three ligament types help stabilize the knee: the anterior cruciate ligament (ACL) in the front, the posterior cruciate ligament (PCL) in the back and the collateral ligaments that run along the sides of the knee. These ligaments prevent the femur from slipping forward or backwards over the lower bone, the tibia, and also assist in limiting sideways motion and in preventing over-rotation of the joint. Damage to any of these ligaments can cause damage to the underside of the patella’s surface.
The knee joint is cushioned by articular cartilage that covers the ends of the tibia and femur and the underside of the patella. This cartilage helps to protect the joint and allows the bones of the knee to slide freely over each other. Two C-shaped pads of cartilage, the lateral meniscus and medial meniscus, further cushion the joint, functioning like shock absorbers between the bones.
Types of Knee Replacement
Your orthopaedic surgeon can offer you two types of knee replacement surgery: (1) unicompartmental (partial knee replacement) and (2) total knee replacement. The determination as to which type of replacement is right for you is determined in consultation with your orthopaedic surgeon.
Unicompartmental Knee Replacement - There are three compartments in the knee: the medial (inner) compartment, the lateral (outer) compartment and the patellofemoral (kneecap) compartment. Unicompartmental knee replacement is appropriate in cases where only the medial or lateral compartments are damaged. This type of surgery is less common than total knee replacement- only 6-8 patients out of every 100 are good candidates for unicompartmental knee replacement-and it is considered only in particular situations where a single compartment requires replacement. Additionally, the best candidates are older, slim individuals with relatively sedentary lifestyles, not those who are young or active and more likely to stress the joint.
Because a partial replacement involves only one compartment of the knee, the incision through which the surgery is performed can be relatively small (3-4 inches long), as compared to that of a total knee replacement which is about 7-8 inches long. Also, because this type of surgery does not interrupt muscle attachments, post-operative rehabilitation, hospitalization and the time required to return to normal activities is shortened.
Total Knee Replacement - Simply put, total knee replacement involves removing bone and cartilage at the end of the femur (thigh bone) and the top of the tibia (the larger of the two lower leg bones), preparing the freshly cut surfaces to accept the chosen biocompatible prosthesis made of metal on metal, ceramic or polyurethane and inserting the selected implant into the space made by the removal of the diseased bone and cartilage.
The first total knee replacements began during the early 1970’s. Since then, enhanced replacement parts coupled with refined surgical techniques have elevated the procedure to the point where 90% of recipients report improvement following surgery. The advances in prosthetic design have been such that the most recent designs purport to have a survival rate of twenty years in 85-90% of post-operative patients. In fact, although hip replacement surgery began a decade earlier than knee replacement surgery, knee replacement is reported to have a higher success rate and a lower incidence of the need for revision.
The newest frontier in total knee replacements is for orthopaedic surgeons to accomplish the entire surgical procedure described above using a minimally invasive surgical approach. Appropriately termed minimally invasive knee replacement, this technique is still in its early infancy and more challenging to perform than the standard method. This new approach uses a computer-based system to compute the optimal alignment and position of the implant parts which in turn eliminates the need for the orthopaedic surgeon to invade the cavities of the femur and tibia with metal rods to determine alignment-the standard approach to total knee replacement now. However, at this point in time, there is not a large enough sample of minimally invasive post-operative patients from which to draw meaningful conclusions as to what the advantages, disadvantages and outcomes of this surgical approach may be, but prognosticators predict that computer guided surgery is the wave of the future. It is surmised that post-operative hospitalization may be reduced by several days and that the time normally required for impatient rehabilitation may be shortened as well. This approach is unsuitable for obese patients and those evincing very restricted motion or significant deformities of the knee.
Like all surgery, knee replacement surgery should be performed only after all palliative measures have failed and as a last recourse to eliminate debilitating pain and restore function. If you think you may be a candidate for such surgery, discuss your options with your orthopedic surgeon right away. Sometimes, when the inevitable path to increased disability is apparent, an orthopedic surgeon may suggest that you have this surgery sooner than later for a variety of reasons. Don’t wait until you are knee deep in trouble to seek advice. Do it today!
The information in the article is not intended to substitute for the medical expertise and advice of your health care provider. We encourage you to discuss any decisions about treatment or care an appropriate health care provider.
