Let’s get one thing straight right away—knee replacements are often a smart choice. A lot of people have less pain and more mobility after their surgery and rehab. 

“Most people are really happy with it. After they recover they ask, ‘Why didn’t I do this earlier?’ It really is a good surgery,” says Dan Paull, an orthopedic surgeon and founder and CEO of Easy Orthopedics. “But, there are things to be aware of,” he cautions.

A study published in 2018 found that up to 20% of people are unhappy with their knee replacements. Here’s what can play into that dissatisfaction.

1. They rushed into surgery

“There are times when getting stronger and exercising can help get rid of knee pain, but sometimes people jump into surgery when more conservative measures may have worked better for them,” says Jasmine Marcus, a physical therapist with McCune and Murphy Physical Therapy.

What you can do: Marcus recommends exercising and building strength, enlisting the help of a physical therapist if necessary.

Even if you still end up needing surgery, getting stronger can help. “Performing prehab exercises and getting the body—not just the leg in question—as strong as possible tends to improve outcomes after surgery,” says Tom Biggart, a physical therapist, athletic trainer, and strength and conditioning coach with EBM Fitness Solutions.

2. Their expectations were not realistic

Scott M. Schreiber, a chiropractor and nutritionist with MN Spine and Sport, says, “Some patients think the knee replacements are going to ‘fix’ everything and are dissatisfied when they come out of surgery and their knee is more sore than before.” 

What you can do: Understand what your recovery will be like. “I cannot stress this enough—it will take six months to a year of therapy following a knee replacement. The patient will have to do exercises at home and will have to endure some pain while performing exercises,” Schreiber says.

3. They struggled with mental health issues

An analysis of multiple studies found that suffering anxiety or depression before a knee replacements was common among people dissatisfied with their results.

What you can do: The study doesn’t offer recommendations, but it might make sense to discuss your mental health issues with your surgeon or take steps toward treatment before your surgery.

4. They were overweight

According to Paull, 79% of people who have knee replacements are obese or morbidly obese. That extra weight may be wearing out their knees. Plus, inflammation linked to fat tissue could be another source of pain. 

What you can do: Consider trying to lose weight before surgery. “For every pound you gain, that’s four pounds of pressure on your knee,” says Allen Conrad, a certified strength and conditioning specialist with Montgomery County Chiropractic Center. “Keeping your weight in control can have a lasting effect on your knee pain and help prevent future problems.”

The force on your knees can be up to six times your body weight, so even a 10-pound weight loss could ease some strain on your knees. A lot of people think they need knee replacement surgery before they can lose weight—they expect they will be more active afterwards. But studies have found that most people don’t lose a significant amount of weight after the surgery.

5. They weren’t accurately diagnosed

Arthritis can look bad on x-rays, but not be responsible for your pain. Sometimes back or hip pain gets referred to the knee, or your knee pain stems from something other than arthritis.

What you can do: Before undergoing a knee replacement get a second opinion. 

6. They contracted an infection

Infections in knee replacements are rare—just 0.39%, according to one study—but devastating.

What you can do: Research the infection rate for the location you plan to have your surgery. (Search online for the name of your facility and “knee replacement infection rate.”) Paull says that in general, surgical centers have lower infection rates than hospitals. 

7. They had surgical complications

Sometimes the knee replacement isn’t technically done correctly. “The components can rotate a little bit internally. It’s hard to figure that out,” Paull says.

What you can do: Choose a surgeon with a solid track record and a lot of experience.

8. They don’t like the feel of their replacement knee

Knee replacements don’t feel like a normal knee.

Knee replacements don’t feel like a normal knee, Paull says.

What you can do: Talk to your surgeon, and other people who have had their knees replaced, to get an idea of what your replaced knee might feel like. That way, you can be prepared for what to expect if you go forward with the operation.

9. They didn’t stick with rehab

If you don’t get your range of motion to at least 90 degrees after surgery, you’re not likely to be happy with the outcome. “Knee replacements aren’t just something where you get the surgery done. It’s a lot of work,” Paull says.

What you can do: Understand what rehab will involve, and talk to your surgeon about the rehabilitation program offered at your center. “Proper rehab can really determine how well the patient recovers and how well they return to their prior level of function,” Biggart says.