The knee is the largest and strongest joint in the body. It is made up of the lower end of the femur (thighbone), the upper end of the tibia (shinbone), and the patella (kneecap). The ends of the three bones where they touch are covered with a smooth, slippery substance called articular cartilage that protects the bones and allows you to bend and straighten your knee. Two wedge-shaped pieces of cartilage called meniscus act as "shock absorbers" between your thighbone and shinbone. They are tough and rubbery, which helps cushion the joint and keep it stable. The knee joint is surrounded by a thin lining called the synovial membrane, which produces fluid that lubricates the cartilage and reduces friction.
Total knee replacement surgery may become necessary when severe degeneration of the joint occurs due to conditions such as arthritis, avascular necrosis (poor blood flow), trauma, and infection.
Also called "wear-and-tear" arthritis, osteoarthritis is a very common condition. Usually, people develop it in middle age or older. It causes pain, swelling, and stiffness that gradually worsens over time. It can occur in any joint in the body, but it is very common in the knee, causing the cartilage in the joint to slowly degenerate (wear away). If left untreated, the cartilage can wear away completely, causing bone-on-bone rubbing. Pain and joint stiffness make it hard to do everyday things like climbing stairs and walking, and it can also affect productivity at work. There is no cure for osteoarthritis, but early treatment is the best way to maintain an active, healthy lifestyle.
The other major types of arthritis that affect the knee are rheumatoid arthritis and posttraumatic arthritis. Rheumatoid arthritis is a chronic autoimmune disease that attacks multiple joints throughout the body, including the knee joint. It is symmetrical, which means it usually affects the same joint on both sides of the body. In rheumatoid arthritis the synovial membrane that covers the knee joint begins to swell, resulting in knee pain and stiffness. Posttraumatic arthritis develops as a result of an injury such as a broken bone.
The most common symptoms of knee arthritis are pain (which usually develops gradually) and inflammation. Other symptoms may include:
- A stiff and swollen joint, making bending and straightening the knee difficult
- Pain and swelling may be worse in the morning, or after sitting or resting.
- Pain that flares up after vigorous activity, such as exercise
- "Locking" or "sticking" of the knee during movement, caused by loose cartilage fragments. The knee might creak, click, snap or make a grinding noise.
- A feeling of weakness or buckling in the knee due to pain
- Increased joint pain with rainy weather
Diagnosing knee arthritis begins with:
Your physician will ask you a series of questions and is likely to do a physical exam. The physical exam will including examining any specific areas of concern, especially as they relate to the reason for your visit to the office.
Personal and Family Medical History: Your doctor will likely ask you a series of questions relating to your personal medical history and your family's medical history.
Your doctor will perform tests to assess:
- Joint swelling, warmth, or redness
- Tenderness around the knee
- Range of motion
- Instability of the joint
- If there is a grating sensation when you move the joint
- Pain when pressure is placed on the knee
- Gait (walking) issues
- Any signs of injury to the muscles, tendons, and ligaments surrounding the hip
- Involvement of other joints (an indication of rheumatoid arthritis)
A form of electromagnetic radiation with very high frequency and energy. X-rays are used to examine and make images of things such as the bones and organs inside the body.
X-rays of an arthritic knee may show a narrowing of the joint space, changes in the bone, and the formation of bone spurs (osteophytes).
Other imaging tests may be performed to better determine the condition of the bone and soft tissues of your knee. These include:
Magnetic resonance imaging (MRI)
This test uses a magnetic field, radiofrequency pulses, and a computer to produce detailed images of body structures in multiple places. You may be asked to drink a contrast solution for better imaging, and you will most likely lie on a moving table as pictures are taken. MRI is a more detailed tool than x-ray and ultrasound and for certain organs or areas of the body, it provides better images than CT. MRI may not be recommended if you have a pacemaker or other metal implant.
Computed tomography (CT) scan
CT scans use x-ray equipment and computer processing to produce 2-dimensional images of the body. The patient lies on a table and passes through a machine that looks like a large, squared-off donut. Doctors order CT scans when they want to see a two-dimensional image of the body to look for tumors and examine lymph nodes and bone abnormalities. If contrast dye is used to improve the computer image, the patient may need to avoid eating or drinking for 4 to 6 hours before the test. Patients should tell their provider before the test if they have any allergies or kidney problems.
Bone scans involve a low dose of radioactive material that is injected into a vein. Bone attracts this material. Concentrated areas show up on the scan and are referred to as "hot spots." Hot spots may be indicative of cancer arthritis.
A common tool for disease screening, blood tests provide information about many substances in the body, such as blood cells, hormones, minerals, and proteins.
There is no cure for knee arthritis but there are a number of treatments that may help relieve the pain and disability it can cause.
As with other arthritic conditions, initial treatment of knee arthritis is nonsurgical. Your doctor may recommend a range of treatment options.
Activity modification: Physicians may prescribe general lifestyle changes to a patient, in order to help relieve the symptoms of their condition and improve their overall physical function and well-being. Depending on the medical condition being treated, activity modification may include: decreasing or increasing one's level of physical activity; added rest; beginning a new activity or exercise program; changing sleep habits; or modifying one's physical environment at home, in their vehicle, or at work.
Some changes in your daily life can protect your knee and slow the progress of arthritis:
- Minimize activities that aggravate the condition, such as climbing stairs.
- Switching from high impact activities (like jogging or tennis) to lower impact activities (like swimming or cycling) will put less stress on your knee.
- Losing weight can reduce stress on the knee joint, resulting in less pain and increased function.
Sometimes referred to simply as "PT," this is a type of rehabilitative treatment that uses specially designed exercises and equipment to help patients preserve, regain, or improve their physical abilities following injury, disability, disease, or surgery. Physical therapy can include therapeutic exercise, massage, walking aids, and patient education and training.
Using devices such as a cane, wearing shock-absorbing shoes or inserts, or wearing a brace or knee sleeve can be helpful. A brace assists with stability and function, and may be especially helpful if the arthritis is centered on one side of the knee. There are two types of braces that are often used for knee arthritis: An "unloader" brace shifts weight away from the affected portion of the knee, while a "support" brace helps support the entire knee load.
Other nonsurgical approaches may include:
- Applying heat or ice
- Pain-relieving ointments or creams
- Wearing elastic bandages to provide support to the knee
- Medications such as:
- Over the counter medication such as acetaminophen
- Nonsteroidal anti-inflammatory drugs (NSAIDs): A class of medications, including but not limited to aspirin, naproxen, and ibuprofen, that are used for reducing pain and redness, swelling, and heat (inflammation) in arthritis and other painful inflammatory disorders.
- Corticosteroids: Cortisol is a naturally-occurring hormone in the body that can affect immune cells. Corticosteroids can be given orally (as a pill) or topically (as a cream, gel, or ointment). Because topical corticosteroids are applied directly to the skin and not circulated throughout the body, patients being treated with them may experience fewer side effects.
- Viscosupplementation involves injecting substances into the joint to improve the quality of the joint fluid.
- Glucosamine and chondroitin sulfate: Glucosamine is found naturally in the body. It stimulates the formation and repair of articular cartilage. Over-the-counter supplements come from animal sources. Chondroitin sulfate is another natural substance found in the body. It prevents other body enzymes from degrading the building blocks of joint cartilage.
- Alternative therapies including acupuncture and magnetic pulse therapy
Types of Knee Replacement
Your doctor may recommend surgery if your knee pain causes disability and is not relieved with nonsurgical treatment. There are many different types of knee surgery available. There are also many different materials that may make up a total joint replacement - including metal and plastic - and the best solution varies from person to person. Your doctor will discuss all of your options with you.
X-ray image showing an artificial knee joint replacement in a patient who suffered from osteoarthritis.
This surgery consists of removing the damaged parts of the knee and replacing it with a smooth artificial surface that is designed to mimic the rolling, gliding motion of a healthy knee. The new prosthesis is customized to the individual, taking into consideration their age, weight, general health, and activity level. The goal of surgery is to alleviate pain and restore function in the damaged knee joint.
Partial Knee Replacement
Also called "knee resurfacing," this is an alternative to total knee replacement. It allows the patient to retain part of their original knee joint while also receiving some new, artificial parts. Partial knee replacement can be a good option for patients with active lifestyles, allowing them to return to their normal activity levels prior to the onset of their knee pain.
After any type of knee surgery, there is a period of recovery. Your recovery time and rehabilitation will depend on the type of surgery you had. Your doctor may recommend physical therapy as well as use of walking aids such as a walker, crutches, or a cane. After a period of time, you should be able to perform simple, daily tasks again with less pain.
If you would like additional information about joint replacement surgery at BMC or wish to make an appointment, please call 617.830.3973.