Anatomy of the Knee
Healthy knees are vital elements in the performance of most everyday activities. They are the largest joints in your body; joints being the areas where two bones, or more, meet. Your knee is an interesting mechanism, with structures working together for the ensurance of smooth and natural movement and function. Basically, your knee is a pair of long bones of the leg held together by tendons, ligaments, and muscles. A layer of cartilage covers each bone end, absorbing shock while protecting the knee.
Two groups of muscles play a part in the knee. At the front of your thigh are the quadriceps muscles; these straighten your leg. At the back of your thigh are your hamstring muscles; these bend your leg at your knee. Along with the muscles, tendons and ligaments are required for proper function of movement. Your tendons are cords of tough connective tissue joining muscles to bones. Ligaments are more elastic; they are bands of tissue connecting bone to bone. Some of your knee’s ligaments provide stability while protecting the joints. Others limit the movement of the shin bone, or tibia, in a forward and backward motion.
Components of the knee include:
- Tibia: the shin bone, which is the larger bone found in your lower leg
- Femur: the thigh bone, which is your leg’s upper bone
- Patella: Your kneecap.
- Cartilage: A variety of tissue covering the bone’s surface at a joint. It helps reduce friction when a joint moves
- Synovial membrane: This is a tissue lining the joint, sealing it within a joint capsule. It secretes synovial fluid, which is sticky and clear, around your knee, lubricating it.
- Ligament: Tough, elastic tissue that connects bones to bones, surrounding the knee to provide support and limit its movement.
- Tendon: A tough type of connective tissue connecting bones to muscles, helping ot control the knee’s movement.
- Meniscus: A curved portion of the cartilage found in knees and other joints. C-shaped, it acts like the knee’s shock absorber, increasing contact area while deepening the joint of the knee.
Common Causes of Knee Pain
Knee pain, a common complaint, can impact people of any age. It may appear as a result of an injury, something like torn cartilage or a ruptured ligament. Medical conditions may also cause pain in your knees; these include arthritis, infections, and gout. The symptoms of knee pain can vary. Signs include redness of the knee joint, warmth when you touch it, swelling of the knee or stiffness there, weakness or instability, inability to straighten your knee fully, and noises such as popping or crunching.
The injuries that can cause pain in your knees are varied. They include ACL injuries, which refer to a tearing of your anterior cruciate ligament. This is one among four ligaments connecting your shinbone and your thigh bone. ACL injuries are particularly experienced in people who play sports like soccer or basketball; these require abrupt changes in direction. Fractures are another injury of the knee.
The bones, including the patella, may be broken during falls or motor vehicle collisions. Those with bones weakened by osteoporosis can occasionally sustain a knee fracture simply by taking a step wrong. A torn meniscus can occur if you twist your knee suddenly while it is bearing your weight. Knee bursitis may be the result of an injury; it causes inflammation in the bursae, which are small fluid sacs cushioning the exterior of the knee joint. These bursae permit the smooth gliding of the ligaments and tendons over the joint. Finally, an injury likely to strike the knee is patellar tendinitis. This inflammation and irritation of the patellar tendon often strikes runners, cyclists, skiers, and anyone in a jumping sport or activity.
Sometimes mechanical problems afflict the knee joint. These causes of pain include a loose body, which involves injury or bone or cartilage degeneration causing a piece of cartilage or bone to break away, floating in the space of the joint. This only causes problems when it interferes with the movement of the knee. The knee then is rather like a door hinge with a pencil caught in it. A dislocated kneecap may also be the source of knee pain. This occurs when the patella slips from its place, generally to the knee’s outside. Sometimes, this dislocation is visible to the naked eye.
Hip or foot pain can also be a mechanical problem that affects the knee. Because of these kinds of pain, you may change the way you walk to spare them. This alteration of your gait may place further stress on the knee. In these cases, hip or foot problems can result in knee pain. Finally, iliotibial band syndrome can hurt the knee, especially in distance cyclists and runners. It occurs when the iliotibial band, which is tough tissue extending from your hip’s outside to your knee’s outside, grows so tight that the result is rubbing against the femur’s outer portion.
rthritis exists in over 100 types, but only a few are likely to impact your knee. One is osteoarthritis, also known as degenerative arthritis. The most common variety of arthritis, this condition occurs when wear and tear in your knee cause its deterioration with age and use. Gout is another; it occurs when there is a build-up of uric acid crystals in your knee. Rheumatoid arthritis is the arthritis in its most debilitating form. It is a condition that is autoimmune and can impact nearly any joint within your body, including the knees.
Pseudogout is often mistaken for gout; it is caused not by uric acid crystals but calcium-containing crystals. They develop in the fluid of the knee, which is the most common joint to be affected by pseudogout. Finally, septic arthritis is a type of arthritis striking the knee. Sometimes the knee becomes infected. This leads to pain, swelling, and redness. Septic arthritis generally occurs with your fever, causing extensive damage to your knee cartilage.
Other Knee Pain Causes and Risk Factors
A general term referring to pain that arises between the patella and its underlying femur is patellofemoral pain syndrome. It is commonly found in athletes, in young adults whose kneecap encounters maltracking, and in older adults, who develop it as a result of patellar arthritis.
Risk factors of knee pain include carrying excess weight on the body. Overweight and obese people have increased knee joint stress, even in such ordinary activities as using stairs or simply walking. Lack of muscle strength or flexibility increases the risk of injury to the knee. Strong muscles stabilize and protect the joints, while muscle flexibility aids in achieving a full range of motion. A previous injury also increases your likelihood of re-injury. Finally, some sports and occupations put more stress on the knees than others. These include, for the former, sports like alpine skiing and basketball, and for the latter, jobs like farming or construction, which place repetitive stress upon the knees.
Overview of the Procedure
Types of Knee Replacement
Four types of knee replacement are available. These options feature total knee replacement, where the entire knee is replaced; partial or unicompartmental knee replacement; where only those parts of the knee which are affected are replaced; kneecap replacement or patellofemoral arthroplasty, which replaces the kneecap; and bilateral knee replacement, where both knees receive simultaneous replacement.
In addition to the different types of surgery, there are different kinds of new knee joints for you to consider. Along with your doctor, your orthopedic surgeon will assist you in deciding the best choice for you. They will consider your knee’s condition and your overall health when making this decision with you.
If arthritis only affects a single side of your knee, you can have a unicompartmental or partial replacement. This is a half-knee replacement. It involves less interference than a total knee replacement has on your knee. This results in better function and a quicker recovery. A smaller incision is involved with this surgery, using techniques called minimally invasive or reduced invasive surgery. The smaller incision might further cause a recovery time reduction. This surgery is not for everyone. You need healthy, strong ligaments in your knee; unfortunately, sometimes this is not known before the incisions are made for the surgery.
Description of Knee Replacement
Also known as knee arthroplasty, a more accurate term for a knee replacement might be knee resurfacing. After all, the bones are not wholly replaced; only their surfaces are. This procedure has several basic steps. The first is to prepare the bone surfaces. Your surgeon removes damaged cartilage located on the surface at the femur’s and tibia’s ends, along with small amounts of underlying bone. Then the surgeon positions the metal implants. This involves replacing the removed bone and cartilage with metal components. These recreate the joint’s surface; they may be cemented into the bone or press-fit there.
Third, the patella needs to be resurfaced. The undersurface of the kneecap gets cut and resurfaced; the surgeon uses a plastic button. However, some surgeons do not perform step three, depending on the case’s condition. Finally, the surgeon inserts a medical-grade plastic spacer between the metal components. This creates a gliding surface that is smooth.
Is Knee Replacement Right for You?
Total knee replacement is a surgery considered for patients who have knee joints that have received damage from trauma, progressive arthritis, or rare destructive joint diseases. Osteoarthritis is the most prevalent reason in the United States for knee arthroplasty. What these causes have in common is that the result is progressively increasing stiffness and pain while daily function decreases. At this point, it is time for many to consider total knee replacement.
The time might be right for you to consider knee arthroplasty when medications cease to help in easing your pain. When even the strong anti-inflammatory drugs do not work, relief might need to be sought in surgery. This is also true of the circumstances when other options that are less invasive do not work. These can include cortisone injections, rest, physical therapy, and lubricating injections. If your pain is debilitating, it may be time for surgery. When you find yourself struggling to perform certain tasks only with difficulty and pain, this is often the case. Such tasks include getting dressed, bathing, rising from a chair or your bed, or climbing stairs.
Other factors indicating that the time is right for knee replacement surgery include needing a cane’s or walker’s aid to get around, your pain being severe both night and day, even when not using the knee joint, or your knee joint is deformed. This latter may be due to injury or because of arthritis. If it bows in or out severely, surgery can become more difficult. When severe deformity is present, seek help sooner. Finally, it might be time if you are between the ages of 50 and 80. Most knee replacements occur on patients in this age range, although age is not a deciding factor in many. Surgeons perform this procedure on patients who run a wide range of ages.
There are other times when you might decide that it is not yet time for knee surgery. You may still have time for more conservative treatments to have a chance, for instance. If rest, heat, ice, exercises to strengthen the muscles, and medications for pain help, keep using these tools instead. If your pain is bearable with medications that still help, you can delay. This is also true if you can get around well with little difficulty in performing your daily activities. If you are very overweight, have weak muscles in your thighs that would not support new knee joints, or if you have open sores or ulcers in the impacted region that might become infected post-surgery, you and your doctor may decide against it.
When is Surgery Recommended?
Forms of arthritis such as osteoarthritis and rheumatoid arthritis can cause the knee pain and deformity. Not everyone who suffers from knee arthritis is right for total knee replacement, however. Doctors use certain guidelines when deciding whether or not to recommend this surgery. Eligible patients experience knee pain that is interfering with their daily living without responding to non-surgical treatments such as bracing, injections of steroids or lubricants, or physical therapy. They also have severe to moderate arthritis in the knee. This is confirmable with medical imaging.
In general, typical candidates also have a combination of difficulty walking, rising from and sitting down in chairs, and using stairs; severe to moderate pain even at rest, which might impact sleep; a deformity of the knee or knees, such as knock-knees or bow-legs, resulting from or exacerbated by the degeneration of the knee; and swelling and inflammation of the knee that is chronic and uncontrolled by rest or medication.
An orthopedic surgeon will evaluate your case and condition. This consists of a number of components. The first is a medical history. The orthopedic surgeon gathers information regarding your general health, asking about the breadth of your knee pain along with your ability to function with it. Then comes a physical examination. Your surgeon assesses knee motion, strength, stability, and leg alignment overall. X-rays come next; these images help your orthopedic surgeon determine your knee’s extent of deformity and damage. Other tests follow. These may be an MRI, a magnetic resonance imaging scan, or blood tests.
After the test results have received the surgeon’s review, the orthopedic surgeon will speak to you about those results, discussing whether or not you are an eligible candidate for such surgery or if other treatment options would best suit your case. You will also hear the potential risks involved in the surgery and the time following the surgery, while you recover and beyond. It is important to have realistic expectations when it comes to total knee replacement surgery. Most of those who have received the surgery are relieved to find a dramatic reduction in their knee pain with a significant improvement surrounding the category of normal daily life activities. What this surgery does not do, however, is permit more than you could do before the arthritis developed.
Possible Complications in Surgery
In fewer than two percent of patients, serious complications occur. While the complication rate is low, surgery always carries the risk of complications. If you have concerns about this, discuss them with your surgeon before the procedure. Remember that chronic illnesses can increase the likelihood of complications, and that, although they are uncommon, when they occur, these complications can limit or prolong recovery.
Infection is one such complication. It can occur in the wound. An infection may also strike deep about the prosthesis. Such a problem can strike within days, weeks, or even years of a surgery. While generally treated by a doctor with antibiotics, deep or severe infections may call for further surgery. The prosthesis may even require removal. Infection anywhere in your body can develop and then spread to the knee joint replacement.
Blood clots are another complication. One of the most common problems that can occur in knee replacement surgery, leg blood clots can be life-threatening. This happens when they break away and then travel their way to your lungs. Your surgeon will give you a prevention program, entailing such things as regularly elevating your legs, performing lower leg exercises for the increasing of circulation, snug support stockings, and blood-thinning medications.
Implant problems may also occur, despite the fact that implant designs and the materials of which they are constructed continue to advance. Surfaces may also wear down, their components loosening. The knee may also scar, limiting motion. Further problems include bleeding, fracture, continued stiffness post-surgery, neurovascular injury, which is an injury to the blood vessels or nerves around your knee during surgery, and continued pain after surgery.
How to Prepare for Surgery
Consuming Medications and Food
After your doctor has explained the details of the total knee replacement surgery to you, you will sign a release form for the treatment. Your doctor will advise you if you should halt the use of certain medications or dietary supplements prior to your procedure. Most likely, you will be instructed to avoid food or drinks other than water after midnight on the day of your surgery.
You may need to use a walker or crutches for several weeks following the procedure. Arrange for these prior to the procedure and ensure the floor plan of your living spaces has room to move around with these. You should arrange for a ride to get back from the hospital as well as assistance for everyday tasks. You will need help with cooking, laundry, and bathing, among other tasks. If you happen to live alone, a hospital discharge planner may suggest a potential temporary caretaker
While looking at the arrangement of your home, create a living space on one floor. Climbing stairs will be challenging at first. Have safety bars installed in your bathroom and a secure handrail in your bath or shower. Double-check that stairway handrails are solidly secure. Acquire a stable chair; this should have a firm seat and back cushion. A footstool will help you keep your leg elevated. Get a bench or chair for the shower, arranging for an elevated toilet seat if your toilet is low. Finally, remove loose cords and rugs.
Get your teeth checked prior to a knee replacement surgery. While the incidence of infections post-surgery is low, infection can still strike if bacteria should enter your bloodstream. This can occur through unresolved poor dental care. If you will need extractions or periodontal work, complete it before the knee operation. Next, a urological evaluation is important if you have recently had a urinary infection or if you have a history of such infections on a frequent basis.
What Happens During Your Hospital Stay
Before the Surgery
First comes anesthesia. Your preference and input assist the team in deciding whether they should use general anesthesia on you, which renders you unconscious, or instead an option that leaves you aware but unable to register pain from the waist down, spinal anesthesia. Before, during, and post-surgery, you receive an antibiotic intravenously. This helps protect against post-surgical infection. A nerve block may also be administered to numb the knee. This numbness gradually wears off following the procedure.
During the Surgery
Because all surfaces of the joint need to be exposed for the surgery, your knee will be positioned in a bent fashion. After an incision is cut that stretches between six to ten inches in length, your orthopedic surgeon moves the kneecap aside to cut away the damaged surfaces of your knee joint. After a preparation to the surfaces, your surgeon attaches the artificial joint’s pieces. Prior to closing the incision, the surgeon rotates the knee and bends it, testing it so that proper function is ensured. The procedure requires about two hours to perform.
After the Surgery
Once you are removed from the anesthetic after you are closed up, you are taken into a recovery room. Provided all goes well, you will be there from one to two hours. You then travel to your hospital room. In most cases, you will have a stay of a couple of days. Your surgeon will prescribe medications to help control your pain. While you are in the hospital, you will be encouraged to regularly move your ankle and foot. This increases the flow of blood to the muscles of your leg, preventing swelling as well as blood clots. Compression boots, support hose, and blood thinners may be used to further prevent swelling and clotting.
Pain-killing medications may include NSAIDs, or nonsteroidal anti-inflammatory drugs, acetaminophen, opioids, and local anesthetics. Your doctor may prescribe these individually or in combination, generally preferring to minimize any need for opioids. A caveat of taking pain medications is that while opioids do help relieve post-operative pain, they are a potentially addictive narcotic. Opioid dependency, along with overdose, is a critical health issue in the United States. Use opioids only as directed and stop taking them as soon as your pain begins to ease.
The day following surgery, at most, you will meet with a physical therapist. Sometimes you meet with this type of specialist hours after your surgery. A physical therapist teaches you specific exercises that will strengthen your leg, restoring knee movement. The end result of these exercises is normal walking and daily activities. Follow these exercises at home as you continue recovering.
Post Surgery Care
For the optimal outcome following your total knee replacement, you need to continue in outpatient physical therapy and follow the wound care instructions given by your hospital team. It is important that you continue exercising the muscles that surround the replaced joint for the prevention of scarring and contracture, maintaining muscle strength so the joint receives stability. Such exercises can reduce your recovery time and lead to the best possible results. The surgical staff will monitor the wound for healing. You should also keep an eye out for signs of infection. These include abnormal redness, swelling, increasing warmth, and unusual pain. Report any such signs, as well as injuries to the joint, at once to your doctor.
How to Avoid Problems Following Knee Surgery
Move around as directed to prevent blood clots and encourage healthy muscle repair. Moving the ankle and foot is also helpful, so do not neglect exercises that include them. Wear support hose or compression devices if you are instructed to do so. Know the signs of a blood clot. The warning signs include increasing calf pain, tenderness accompanied by redness below or above your knee, and swelling that is new or increasing in your foot, ankle, and calf. A warning sign of a pulmonary embolism, when a blood clot has made its way to your lung, feature abrupt shortness of breath, localized chest pain accompanied by coughing, and abrupt onset of chest pain.
Avoid falls following your surgery. Use care when moving around, but do not neglect motion. Exercise is critical in recovery, particularly in the first few weeks following surgery. Three to six weeks after the surgery, you ought to be capable of resuming most normal functions of life. Your hospital team will instruct you in the use of assistive aids following your surgery.
Knee Surgery Outcomes
While an improvement to your knee’s range of motion is a goal of replacing your knee, restoration of full motion does not often occur. Most patients are able to straighten their new knees almost fully, bending them sufficiently to enter and exit a car or to climb stairs. Kneeling can be uncomfortable but does not harm the joint.
Numbness in the skin around the incision is not uncommon; neither is stiffness when excessive bending is practiced. Most people also hear or feel clicking in the plastic and metal while walking or bending the knees. This is normal and often diminishes with time. The new knee may set off security-placed metal detectors in airports and other secure buildings. Inform the security agent that you have had a knee replacement surgery if this takes place.
Extending the Life of a Knee Replacement
At present, greater than 90% of modern knee replacements still function well a full 15 years post-surgery. Follow your orthopedic surgeon’s instructions upon completion of your operation. Take care to protect the knee replacement and your health in general. When well-cared for, a new knee replacement should last at least 20 years, if not longer. A partial knee recovery may require further surgery after about ten years. These are important ways to contribute to the continuing success of your procedure.