While age is a major risk factor for osteoarthritis of the knee, young people can get it, too. For some people, it may be hereditary. For others, osteoarthritis of the knee can result from injury or infection or even from being overweight. Here are answers to your questions about knee osteoarthritis, including how it's treated and what you can do at home to ease the pain.
What Is Osteoarthritis?
Osteoarthritis, commonly known as wear-and-tear arthritis, is a condition in which the natural cushioning between joints – cartilage – wears away. When this happens, the bones of the joints rub more closely against one another with less of the shock-absorbing benefits of cartilage. The rubbing results in pain, swelling, stiffness, less ability to move, and, sometimes, the formation of bone spurs.
Who Gets Osteoarthritis of the Knee?
Osteoarthritis is the most common type of arthritis. While it can occur even in young people, the chance of getting osteoarthritis rises after age 45. More than 32 million people in the U.S. have osteoarthritis, with the knee being one of the most commonly affected areas. Women are more likely to have osteoarthritis than men.
What Causes Knee Osteoarthritis?
The most common cause of osteoarthritis of the knee is age. Almost everyone will eventually have some degree of osteoarthritis. But several things increase the risk of having significant arthritis at an earlier age.
- Age. The ability of cartilage to heal decreases as a person gets older.
- Weight. Weight increases pressure on all the joints, especially the knees. Every pound of weight you gain adds 3 to 4 pounds of extra weight on your knees.
- Heredity. This includes genetic mutations that might make a person more likely to have osteoarthritis of the knee. It may also be due to inherited abnormalities in the shape of the bones that surround the knee joint.
- Gender. Women ages 55 and older are more likely than men to get osteoarthritis of the knee.
- Repetitive stress injuries. These are usually a result of the type of job a person has. People with certain occupations that include a lot of activity that can stress the joint, such as kneeling, squatting, or lifting heavy weights (55 pounds or more), are more likely to get osteoarthritis of the knee because of the constant pressure on the joint.
- Athletics. Athletes involved in soccer, tennis, or long-distance running may be at higher risk for osteoarthritis of the knee. That means athletes should take care to avoid injury. But it's important to note that regular moderate exercise strengthens joints and can decrease the risk of osteoarthritis. In fact, weak muscles around the knee can lead to osteoarthritis.
- Other illnesses. People with rheumatoid arthritis, the second most common type of arthritis, are also more likely to get osteoarthritis. People with certain metabolic disorders, such as iron overload or excess growth hormone, also run a higher risk of osteoarthritis.
What Are the Symptoms of Knee Osteoarthritis?
Symptoms of osteoarthritis of the knee may include:
- Pain that increases when you are active, but gets a little better with rest
- Stiffness in the knee, especially in the morning or when you have been sitting for a while
- Less mobility of the knee, making it hard to get in and out of chairs or cars, use the stairs, or walk
- A creaking, crackly sound that is heard when the knee moves
How Is Osteoarthritis of the Knee Diagnosed?
The diagnosis of knee osteoarthritis will begin with a physical exam by your doctor. Your doctor will also take your medical history and note any symptoms. Make sure to note what makes the pain worse or better to help your doctor determine if osteoarthritis, or something else, may be causing your pain. Also find out if anyone else in your family has arthritis. Your doctor may order more tests, including:
- X-rays, which can show bone and cartilage damage as well as the presence of bone spurs
- Magnetic resonance imaging (MRI) scans
MRI scans may be ordered when X-rays do not give a clear reason for joint pain or when the X-rays suggest that other types of joint tissue could be damaged. Doctors may use blood tests to rule out other conditions that could be causing the pain, such as rheumatoid arthritis, a different type of arthritis caused by a disorder in the immune system.
How Is Osteoarthritis of the Knee Treated?
The primary goals of treating osteoarthritis of the knee are to relieve the pain and make you more mobile. The treatment plan will typically include a combination of the following:
- Weight loss. Losing even a small amount of weight, if needed, can significantly decrease knee pain from osteoarthritis.
- Exercise. Strengthening the muscles around the knee makes the joint more stable and decreases pain. Stretching exercises help keep the knee joint mobile and flexible.
- Pain relievers and anti-inflammatory drugs. This includes over-the-counter choices such as acetaminophen, ibuprofen, or naproxen sodium. Don't take over-the-counter medications for more than 10 days without checking with your doctor. Taking them for longer increases the chance of side effects. If over-the-counter medications don't provide relief, your doctor may give you a prescription anti-inflammatory drug or other medication to help ease the pain.
- Injections of corticosteroids or hyaluronic acid into the knee. Steroids are powerful anti-inflammatory drugs. Hyaluronic acid is normally present in joints as a type of lubricating fluid.
- Alternative therapies. Some alternative therapies that may be effective include topical creams with capsaicin; acupuncture; or supplements, including glucosamine and chondroitin or SAMe.
- Using devices such as braces. There are two types of braces: "unloader" braces, which take the weight away from the side of the knee affected by arthritis; and "support" braces, which provide support for the entire knee.
- Physical and occupational therapy. If you are having trouble with daily activities, physical or occupational therapy can help. Physical therapists teach you ways to strengthen muscles and make your joints more flexible. Occupational therapists teach you ways to do regular, daily activities, such as housework, with less pain.
- Surgery. When other treatments don't work, surgery is a good option.
When Is Surgery Used to Treat Knee Osteoarthritis?
If your doctor wants to treat the osteoarthritis in the knee with surgery, the options are arthroscopy, osteotomy, and arthroplasty.
- Arthroscopy uses a small telescope (arthroscope) and other small instruments. The surgery is done through small cuts. The surgeon uses the arthroscope to see into the joint space. Once there, the surgeon can remove damaged cartilage or loose particles, clean the bone surface, and repair other types of tissue if damage is found. The procedure is often used on younger patients (ages 55 and younger) in order to delay more serious surgery.
- An osteotomy is a procedure that aims to make the knee alignment better by changing the shape of the bones. This type of surgery may be recommended if you have damage mostly in one area of the knee. It might also be recommended if you have broken your knee and it has not healed well. An osteotomy is not permanent, and further surgery may be necessary later on.
- Joint replacement surgery, or arthroplasty, is a surgical procedure in which joints are replaced with artificial parts made from metals or plastic. The replacement could involve one side of the knee or the entire knee. Joint replacement surgery is usually reserved for people over age 50 with severe osteoarthritis. The surgery may need to be repeated later if the prosthetic joint wears out after several years. But with today's modern advancements, most new joints will last over 20 years. The surgery has risks, but the results are generally very good.
Platelet-rich plasma (PRP) injections. In this treatment, your doctor takes a sample of your blood and spins it in a machine called a centrifuge to pull out your blood's platelets and plasma. When injected back into the joint, this super-concentrated mixture contains substances that could promote healing.
Even though they're popular with some high-profile athletes, PRP injections still aren’t proven, and the treatment formulations can vary a lot.
It is a treatment that is not recommended because of the lack of standard dosages and preparation.
Mesenchymal stem cells, or MSCs. Your bone marrow makes these types of cells. They can grow into new tissues, including cartilage. By gathering these cells and injecting them into the knee joint, the hope is that they will give rise to new cartilage and reduce inflammation.
It’s a hot area, with clinical trials going on. But most studies are still early.
A review published in 2016 in BMC Musculoskeletal Disorders concluded that MSC-based therapies offer an “exciting possibility” for treatment, but further studies need to work out how they can best be used and how well they work.
Also, they're expensive.
Bone marrow aspirate concentrate. This draws on the same concept as MSCs. Experts take cells from your body and use them to stimulate the healing process inside your knee.
The advantage is that bone marrow may be easier to obtain than MSCs, and it also contains other substances involved in promoting cartilage regrowth and calming inflammation.
While still a new approach, a review in the Orthopaedic Journal of Sports Medicine found “good to excellent overall outcomes” from 11 studies. The researchers noted that that some trials were tougher than others. So they recommended that the treatment be used cautiously since a lot is still unknown.
Autologous cultured chondrocytes. This is a procedure to repair injuries that can lead to osteoarthritis. It involves collecting the cells that form cartilage from your own joints, growing the cells in a laboratory, and then injecting these cells into the knee.
Invented in Sweden in the 1980s, the method has become common in orthopedic practices. The FDA approved the latest generation in December 2016. Called Maci, it puts the cells inside a dissolvable scaffold – placed inside the knee – that’s designed to grow new cartilage.
In a study of Maci involving 144 people, more than 87% of those who got Maci had improvement in symptoms over 2 years, compared with 68% who got a different cartilage-stimulating procedure called microfracture.
Botox injections. Botulinum is a toxin made by the bacterium Clostridium botulinum. Because it can shut down nerve cells, doctors can use it to ease muscle spasms.
Some doctors are trying botulinum to help treat joint pain. The theory is that it might permanently deaden nerves and offer relief. But it wouldn’t affect the knee’s structure.
Does it work? A review of 16 studies published in 2016 in the journal Joint Bone Spine found that the results were conflicting and the studies were too small to draw conclusions.
Water-cooled radiofrequency ablation. This is another experimental procedure to treat pain. It aims to disable the nerves that are causing pain by heating them. “Water cooling” is a way to control the speed of warming. While it’s gotten a lot of publicity, studies so far are limited to small groups of people.