What’s in a knee?
A knee does three things:
- Load transfer. When you’re stepping on the ground, it takes the energy from your foot and transmits it into your spine. Transferring the energy involves a lot of weight moving through your bones, so the cartilage between bones provides some cushioning to help make it easier to transfer the load.
- Mobility. Mobility is motion of the knee. You have large muscles with muscle tendons inserting on the bones around your knee that allow you to straighten and bend the knee.
- Knee stability. Ligaments on the inside and outside of your knee help keep the bones aligned while you’re moving and having load transfer.
What’s knee arthritis?
Knee arthritis, also called osteoarthritis, is a progressive degenerative joint disease which affects over 20% of US adults. In arthritis, the cartilage cushioning the knee has been lost. As the bone is no longer protected, it starts to see increased forces which lead to bone spurs and eventually deformity in the knee.
Knee arthritis typically has knee pain along the joint line, off-center from the middle of the knee. You may also get swelling. As arthritis gets worse, you may get stiffness in the knee where you can’t bend or straighten it as easily or as far as you used to. Finally, some people become knock-kneed or bow-legged if they have lost enough cartilage on one side of the knee.
Is all knee pain from arthritis?
Not all knee pain in older adults is due to arthritis, but a lot of it is. Some other causes include:
- Patellofemoral syndrome, or runner’s knee. It’s a catch-all term for anterior knee pain that’s thought to come from a mismatch between the strength and ability needed to move and extend the knee and how much you have.
- Tendonitis. The tendons around the knee that connect the muscles to the bones may become inflamed.
- Rheumatologic diseases.
- Hip and spine problems.
- Meniscal tearing. Arthritis leads to degenerative meniscal tears. In these cases, the problem is not the meniscus tear itself, but the underlying arthritis that led to the tear.
Meniscal Tears
All patients with severe arthritis will have some kind of meniscal tearing or pathology. As you lose the cushioning (cartilage) that’s overlying the bones and the bones get closer together, it’s almost impossible for the other structures between the bones, like the meniscus, to not have some level of pathology.
Treating the underlying arthritis is generally better than treating just the meniscal tear, because treating the tear won’t solve the root cause. Rarely is the tear so significant that it would be treated itself. If you have that rare case, you’ll want to talk with your surgeon.
Arthritis and Other Problems
Arthritis can and does coexist with other issues. You may have knee osteoarthritis but may also have tendonitis around the knee or patellofemoral syndrome.
How do you know if your pain is arthritis?
- Symptoms. Are the symptoms in your knee along the joint line or along a tendon? Arthritis symptoms are more likely to be along the joint line.
- Exam. An exam can be very helpful to know if there’s tenderness over the joint line itself or over one of the tendons. Is there swelling? Is the swelling on the inside of the knee or the outside of the knee?
- X-rays. X-rays are one of the most important ways to diagnose arthritis. When bones on an x-ray have lost all of their cushioning and are touching on the x-ray with no space between them, it is sometimes called bone-on-bone arthritis.
- Rule out other diagnoses. More than one condition may be affecting your joint at one time, and joints can influence each other. You may need to get x-rays of the hip, for example, to make sure a hip issue isn’t contributing to the knee pain.
- Diagnostic injection. We normally think of injections as being therapeutic, or a treatment, but they can be helpful diagnostically. If the pain doesn’t go away when you receive an injection that is supposed to numb the pain, it may be a sign to look elsewhere for other causes of the pain.
Diagnosing the cause of the pain isn’t always straightforward. To help patients with knee pain, the patient symptoms, the exam, and the imaging all are put together to find the best sense of what is causing the knee pain.
Should I get an MRI?
It’s not needed for arthritis. However, you do want to get the right kind of x-rays. Some x-ray views show the relationship between the bones at the joints in more clarity than other views, so a knee that looks like more moderate arthritis in one view can be shown to have severe arthritis in another view. If you’ve had x-rays previously, your surgeon may send you for additional ones to ensure that they are the right kind of view.
What are the treatments for knee arthritis?
- Over the counter medications like Tylenol and ibuprofen.
- Physical therapy and low-impact quad strengthening won’t reverse your arthritis, but they can help give the knee more stability and reduce symptoms.
- Maintaining a healthy weight can be very helpful in reducing the amount of load that’s having to go through the diseased cartilage.
- Activity modification involves doing the activities you want to do in ways that won’t cause knee pain.
- Assist device use isn’t for everyone, but a cane or walker can be a part of helping take some of the load off of the arthritic knee and reduce symptoms.
- Bracing.
- Steroid injections.
None of the treatments will reverse arthritis, but they can help control symptoms and help you live the kind of life you want.
What treatments don’t work for knee arthritis?
- Opioids may have a short-term effect, but this is a chronic problem.
- Draining the knee reduces the fluid, but the fluid is just a symptom of the underlying arthritis. While draining the knee may provide some very, very short-term symptom relief, it’s not a great treatment.
- Vitamins and supplements have not been shown to work effectively long term.
- Stell cell injections may help in the future, but cannot regrow cartilage.
- “Clean-up” knee arthroscopy may be useful in a limited role in very select circumstances, but not as a general recommendation.
Who needs a knee replacement for arthritis?
Getting a knee replacement for knee arthritis is a quality-of-life issue. If the non-operative treatments are not working and your quality of life is limited, you can discuss the potential benefits of the knee replacement versus the risk with your doctor.
What is a knee replacement?
In a knee replacement, the ends of the bones with diseased cartilage are cut off and replaced with metal caps. A plastic piece is put between the metal caps so the joint can move smoothly.
There are one million knee replacements performed annually in the United States, and they can be performed with brief hospital stays or same-day procedures. The recovery is in stages: 80%+ of the recovery is generally during the first three months, but patients continue to improve up to one year after surgery.
Frequently asked questions
Does arthritis change the shape of your knee and your leg?
It can. The most common pattern of arthritis in the knee is the cartilage on the inside of the knee wears out first, so the knee may start to become bow legged. As the arthritis progresses, the knee can start to drift in and stretch the ligaments on the outside of your knee while the ligaments on the inside of your knee become tight and stiffened.
Is it ever too late to have replacement surgery?
No, it’s not, if you’re overall healthy enough for the surgery. Studies of patients in their eighties and nineties who have had knee replacements show that they recover well. There might be slightly higher risk of small complications like urinary tract infections and slightly longer hospital stays, such as 1-2 days instead of 0-1 days. However, it’s important to remember that there is at least a three-month recovery from this surgery.
Is there a way to prevent arthritis entirely or prevent it from getting worse?
Maintaining a healthy weight is probably the best action you can take. Other than weight, there isn’t much you can do to affect it as much arthritis is probably genetic. Studies looked at both avoiding activating and increasing activity and neither helped nor hurt.
If someone has arthritis but their knee isn’t painful, do they need to still act?
No, they don’t. All the non-operative treatments were designed around symptom control. If you don’t have any or many symptoms, there isn’t much to do. Even if someone says you have arthritis on x-ray, you don’t need to act unless it is bothering you.
Is bursitis a form of arthritis?
No, it’s not. With arthritis, the knee can get very swollen and sometimes you’ll get a Baker’s cyst, where some of the fluid from inside the knee leaks out and you’ll see a lot of swelling in the back of the knee. However, that is different from the bursa being inflamed, a little fluid sack designed to cushion tendons. However, like many conditions, someone may have both arthritis and prepatellar bursitis in the knee.
What exercises do you recommend before a knee replacement?
Low impact quad strengthening can be very helpful. Riding on a stationary bike is a helpful way to do it. A physical therapist can help with other routines.
How long does a knee replacement last?
We usually say 20 years, but there are many factors that come into play. If you’re older and less active, 20 years may be a lower estimate. If you’re younger, heavy and very active, it may not last 20 years. They do last long enough that the longevity is not typically a huge driver in the decision making as much as it used to be. One of the fastest-growing groups of people for knee replacement is patients in their fifties, and part of what has driven that is the longevity of the implants.
How soon can someone have a second knee replacement?
There’s no one answer. I tend to wait three months, because most complications will have been caught by then. However, many people wait longer. A year after a knee replacement, someone is completely recovered and they’ve forgotten the details of recovering from the first one and are ready to have the second surgery.