Told to Lose Weight Before a Joint Replacement? Here's Why.

According to The American Academy of Orthopaedic Surgeons (AAOS) “Obesity is one of the most common diseases that adversely affect bone and joint health.” It’s also one of the most common reasons that patients are denied a joint replacement or surgery is postponed. And let’s face it, being denied hip or knee replacement surgery until you lose enough weight is discouraging. Being given a number on the scale to hit before scheduling a surgery feels like another massive roadblock. After all, losing weight isn’t easy--especially when you’re in chronic pain with limited mobility.

With this being said, there are actionable things that everyone can do to drop the required 5 lbs or 50+ lbs before surgery. Before we detail what everyone with “a little something extra” can do to prepare for a joint replacement, it’s important to understand why it’s so important to reduce your BMI before surgery.

According to AAOS, “Individuals with obesity are 20 times more likely to need a knee replacement than those who are not overweight.”

First Thing’s First: What is BMI?

BMI stands for “body mass index”. BMI is calculated by dividing weight over height. The metric calculation is kg/m2 (kg is a your weight in kilograms and m2 is your height in metres). For example if someone weighs 203 lbs (92 kg) and is 5’9” (1.75m) their BMI would be 30. A BMI of 30 or greater is considered obese.

More than two-thirds of adults in the United States are overweight and one in three adults have obesity.

There are numerous calculators online that convert weight (in lbs or kgs) and height (in standard or metric). Here is a helpful, easy-to-use calculator to check your BMI.

BMI Categories:

Having a BMI of 30 or greater may prevent a surgeon from scheduling surgery. However, there is no hard and fast rule. If you fall into the “overweight” category, losing extra weight is always recommended, but may not be required by your healthcare provider.

Once you’ve calculated your BMI, here’s what the medical community would classify your size as. Although BMI is a strong indicator of body fatness, women and older adults tend to have more body fat than men or younger adults with the same weight and height.

  • Underweight— under 18.5
  • Normal weight— between 18.5–24.9
  • Overweight— between 25–29.9
  • Obese— between 30-34.9
  • Severely Obese— between 35-39.9
  • Morbidly Obese— between 40-49.9
  • Super Obese— over 50

People with a BMI of 30 or greater are twice as likely to suffer from hip arthritis than someone who has a BMI under 30. It’s a double-edged sword: people who are overweight are more likely to need a replacement but, due to pain and mobility issues, have a more difficult time losing weight and alleviating pressure from troubled joints.

Why Won’t My Surgeon Perform Surgery if I’m Overweight?

alt news Your surgeon will use your BMI when determining your risk-level for surgery--many of the surgeons we’ve spoken to want to keep a patient’s BMI under 35. If you’re obese, but otherwise perfectly healthy, your surgeon may still move forward. However, if you’re obese with other risk-factors or comorbidities (for example, having diabetes or depression) your care team may determine that a replacement is too risky. Ultimately, since a knee or hip replacement is an elective surgery, your surgeon can afford to hold-off and perform the procedure when your risk of complication is lower.

Patients with obesity are more likely to have certain diseases and conditions that increase the risk of surgery. As outlined by the American Joint Replacement Registry, here are the comorbidities (second diseases or health issues) risk factors that your surgeon will use alongside BMI to assess your overall risk:

  • Alcohol Abuse
  • Anemia (Pre-operative)
  • Cardiac Arrhythmia
  • Cerebrovascular Disease
  • Chronic Liver Disease
  • Chronic Pulmonary Disease
  • Coagulopathy
  • Congestive Heart Failure
  • Dementia
  • Depression
  • Diabetes
  • Drug Abuse
  • Electrolyte Disorder
  • Hemiplegia/Paraplegia
  • HIV Disease
  • Hypercholesterolemia
  • Hypertension
  • Hypothyroidism
  • Ischemic Heart Disease
  • Lymphoma
  • Malignancy
  • Metastatic Tumor
  • Peptic Ulcer Disease
  • Peripheral Vascular Disease
  • Psychoses
  • Pulmonary Circulation Disease
  • Renal Disease

The more secondary conditions you have, the more likely your surgeon is to postpone surgery. Since losing weight, like smoking, is a controllable risk factor, these are the best ways you can proactively reduce risk and improve your odds at a great joint replacement outcome.

Elective is truly the keyword. If you’re not medically fit to have an elective surgery, why would they perform it?

3 BIG Reasons You Should Lose Weight Before Joint Surgery

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1. Fewer Complications After Surgery

According to The American Academy of Orthopaedic Surgeons (AAOS), patients who are obese have “significantly higher rates of complication and hardware failure after total joint arthroplasty (TJA)”. AAOS cites that obesity “affects individual patient care, the healthcare system and nearly every organ in the body.”

Here are some of the specific complications associated with obesity after joint replacement surgery:

Losing extra weight, even just 5-10% of your body weight can significantly improve your recovery time and outcome, and seriously cut complications.

2. Easier Surgery

Obese patients have more difficult surgeries for numerous reasons. First and foremost, the surgery is more challenging for a surgeon to perform due to lower visibility. Veins are harder to find making it harder to administer necessary medications; anesthesia is harder to administer; breathing is more greatly affected; there tends to be more blood loss; and surgery times are longer. With a longer surgery, patients are under riskier anesthetic for a longer time period and there is more opportunity for complication.

A study by the Mayo Clinic, that looked at spine surgery (not joint surgery) found that obese patients had “increased vasoactive drug requirements during surgery, longer anesthetic and operative times, higher ICU [Intensive Care Unit] admission rates, and increased hospital lengths of stay.”

Shedding extra weight means an easier surgery which directly relates to a more seamless recovery and at-home rehabilitation.

3. Less Pressure on New Joint

This is a crazy statistic: each pound of weight loss offloads 5 to 10 pounds from the knee joint depending on what activity you’re doing. High-impact activities like running can put an excess of 10x your weight on your knees. In other words, if you lose 10 lbs this is like relieving your knee joints of 50-100 lbs of excess pressure on your knee joint. As such, weight loss can alleviate pain from your hip or knee. Although a weight loss probably won’t rule out your need for a replacement, it may make you feel a little more comfortable while you waiting your recovery and ReHab.

How to Lose Weight with Joint Pain

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Without a doubt, needing to lose weight while having reduced mobility and chronic joint pain isn’t easy. You’re in a bit of a pickle. However, there are nutritional plans you can follow, daily exercises you can complete from home, and even fairly intense cardio workouts you can do comfortably. With some persistence, a combination of lifestyle changes, and a dash of good ol’ time, you can shed unwanted extra weight.

Here are some things you can do today to start losing weight:

1. Eat More Good, Less Bad.

Did you know that when it comes to losing weight, diet is the number one factor? Although exercise plays an important role, your caloric intake and the types of foods you’re eating matter most.

With the right recipes and by incorporating “superfood” combinations, you can start treating food like medicine that helps your health. Your diet can not only encourage weight-loss, but can naturally reduce swelling and inflammation on your joint.

Here are the superfoods and food groups you should try and eat from. Ditching processed foods, bleached grains (like white rice or bread), sugary foods (like desserts or sauces like Ketchup), and focusing on eating more vegetables and low-fat proteins (like chicken breast or fish) is a good place to start.

Note: Always consult your doctor before drastically changing your diet or starting a new supplement regime.

2. Daily Exercises From Home

Going to the gym or a workout class may be off the table. The good news is with a solid understanding of exercises designed to prepare one’s hip or knee for joint surgery, you can do a safe, effective routine from home. By performing a targeted list of exercises once or twice a day you will strengthen the muscles that will support your new joint, improve flexibility, reduce swelling and blood clot risks, and burn calories! Pair this by setting a walking goal for yourself (like hitting 5000 steps, walking around the block, or even walking around your house), or using a recumbent bike (which is easy on your joints) and you will reap many benefits.

Here’s a list of 10 PreHab exercises designed to get patients who are awaiting a hip or knee replacement ready for surgery.

3. Water Therapy (Pool Therapy)

Water is magic for those needing a replacement. For those with severe osteoarthritis and joint pain who must lose a larger amount of weight, water therapy may be the answer you’ve been searching for. In the pool, depending on the depth of the water, you can unload 50-90% of your body weight. This takes off enormous pressure from your joints, which allows you to perform cardiovascular exercises at an intensity level that wouldn’t be possible on land. Cardio exercises performed at 70-75% of heart rate reserve is great for caloric burn and weight loss.

There are water therapy classes designed for those preparing for joint surgery, as well as those in recovery, in just about every major city. Here is a post on why PreHab Pool Therapy is so fabulous. The post includes listings of recognized water therapy centres by US state.

4. Start a PreHab Program!

A well-rounded, good PreHab program will guide you through numerous ways to get ready for joint replacement surgery. PreHab will center around getting you in the best mental and physical health possible before surgery. By using a PreHab program, like PeerWell’s smartphone PreHab app, you are supported through a laundry-list of healthy changes that’ll prepare you for surgery. As a result of making these healthy changes and completing the outlined daily tasks (exercises, eating tips etc.) can lead to weight loss, among many other benefits.

PreHab is designed to give you daily, small tasks to complete, so the big picture of losing ‘x’ amount weight, or dealing with the stress of surgery, doesn’t become too overwhelming or daunting.


Sign-up for PeerWell today and join the PeerWell blog for early access to content that matters.The more you do before your hip replacement, the more control you have over your outcome and recovery.

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Hi, I'm Grace. I write all things surgery for the PeerWell blog. You may remember me from such titles as: "Diabetes & Joint Replacement 101" & "Sex After a Joint Replacement".

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