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This post was co-authored by Grace McClure and Dr. Nicholas Frisch, M.D., OS, MBA.

After knee replacement surgery, you and your care team will likely zero-in on one crucial measurement during ReHab: range of motion. The increase in your range of motion not only indicates that you’re progressing throughout your recovery, but tells your physical therapist and surgeon a number of things. Hitting range of motion (ROM) milestones indicates that your stiffness has gotten better, swelling has gone down, you are able to manage pain, inflammation is under control, and you are without infection.

If you are hitting the 2 week, 6 week, and 12+ week marks without notable improvements to your knee flexion (a key range of motion measure), this will be taken quite seriously by your care team. Improving range of motion right off the bat is necessary if you want your artificial knee to move naturally, without stiffness and endure everyday activity without pain.

Dr. Frisch adds to the conversation on pain, “One problem I often encounter in patients who are struggle to achieve their range of motion is that their pain is not well controlled. This does not mean you need more opioid pain medication! It means that you may need to spend more time with your surgeon designing a pain protocol that works well for you to maximize your results. This could be adding additional medications, changing certain medications, or simply adjusting the timing and dosage of those medications to more adequately address your pain and allow you to maximize your therapy.”

Haven’t had surgery yet? Get matched (for free) to a top surgeon who has the tools to improve your ROM before surgery. The better your movement before surgery, the easier it will be to gain ROM in recovery.

Here is a quick cheat sheet of the degrees of knee flexion required to do everyday movements:

knee flexion

  • 65° to walk
  • 70° to lift an object from the floor
  • 85° to climb stairs
  • 95° to sit and stand comfortably
  • 105° to tie shoelaces
  • 115° (or greater) to squat or sit cross-legged

A knee flexion of 125° and over is typically the end goal set for total and partial knee replacement patients. A study that measured the knee flexion in 100 knees a year after a total replacement saw a mean flexion of 125°. At this range of motion, most people can carry out almost all normal activities. However, difficulty with squatting or sitting on one’s heels can remain a challenge for knee replacement recipients.

Range of Motion Basics You Should Know

Impress your physical therapist and care team by knowing some of the basic terms and important measures surrounding your range of motion.

Range of Motion— The normal movement of your joint, measured in degrees from the center of your knee. Range of motion (ROM) includes flexion (bending), extension (straightening), adduction (movement towards center of the body), abduction (movement away from center of the body), rotations (inward and outward). ROM is measured using an instrument called a “goniometer”. For instance, a completely straight knee joint measure 0° while a fully bent knee clocks in at about 135° degrees of flexion.

  • Knee Flexion— The measurable degree in which your leg (and knee joint) is bent. Think about laying on your stomach and bending your leg toward your buttocks. This requires knee flexion.
  • Knee Extension— The measurable degree in which your knee is extended. Think of standing on one leg and raising your surgical leg behind you like you’re stepping backwards or karate kicking someone behind you…hiya! This requires knee extension.
  • Active Range of Motion— Moving your knee joint to its maximum potential without any assistance.
  • Passive Range of Motion— When your therapist or a piece of equipment moves your knee through a range of motion without any effort from you.
  • Active Assistance Range of Motion— Moving your knee through a range of motion exercise with some assistance from your therapist of a piece of equipment.
  • Extension Lag— When you cannot extend to a completely straight position (angle of 0°).
  • Flexion Contracture–When you cannot extend your leg, with or without assistance.

Range of Motion Milestones

Range of Motion Milestones

Although there are some things that can predict who will have an easier recovery (such as doing PreHab before surgery), a lot of it boils down to the individual. Some people will hit certain milestones sooner than others. Always remember, that everyone’s recovery is different.

Use the below range of motion milestones as a general guide but stay focused on your own personal goal-setting and ReHab. Regaining full motion and getting back to your new and improved normal typically takes a full calendar year.

Day 1 to 2 Weeks

Data suggests that patients return to the ROM they had before surgery within this timeframe. In saying this, chances are that your range of motion was poor before your replacement. With your new artificial joint you have the ability to gain far more movement. You and your physical therapist will be meeting 2 or more times a week to work on your motion. In addition, you should be working through an at-home, low-impact ReHab routine. It’s important to keep active during this period to avoid stiffness, decrease swelling, and reduce inflammation.

GOAL: 65-90 degree flexion or greater. This means you will be able to stand, walk and go up and down stairs (with your walker or crutches).

2 to 6 Weeks

During this period, it’s likely that your prescribed pain medication dose will be lowered or stopped entirely. It’s also around this time that your physical therapist will increase the intensity and frequency of your exercises and movements. You will have to work through the physical pain as this is a critical time for regaining range of motion.

GOAL: 90 degree flexion or greater. This means that you should be able to go up and down stairs with just one (or no) crutch, walk normally without an assisted device, and should be able to sit and stand more comfortably.

6 to 12 Weeks

Within the 2 to 3 month mark, your range of motion should certainly be better than it was prior to surgery, but is hopefully better than it’s been in a long time. You shouldn’t be experiencing any extensor lag and should have noticeably improved range of motion. Wahoo!

GOAL: 115 degree flexion or greater. You should be able to move around normally, bend down to pick things up, sit comfortably, stand for longer periods of time and be able to tie your shoelaces.

12+ Weeks

The first 90 days are definitive in your recovery. This is when you will be under the watchful eye of your care team, physical therapist, and will require the most support of your family friends. Passing into the 3 month mark and beyond, you’ve hopefully made leaps and bounds, have little pain, and are able to do everyday activities with ease.
You should still be keeping up with range of motion exercises, walking longer distance, and most importantly, challenging yourself to do more and more.

GOAL: 115 degrees to 135 degrees. For those fully recovered, ideal flexion is around 125-135 (give or take a little on either end).

How to Improve Your ROM

According to the data, 5% to 7% of knee replacement patients develop stiffness after surgery. Stiffness can require additional surgery or mean that a recipient won’t ever get the full benefit of their artificial knee.

The best thing you can do to avoid stiffness is to improve your range of motion by keeping up the good work. In other words, there is no quick fix. Building range of motion takes continued effort and continuing to set bigger and badder goals for yourself.

Here are some of the top things you should be doing to improve your ROM after surgery:

ReHab at Home

The couple of hours of physical therapy you will do each week with your physical therapist isn’t going to cut it. You need to be supplementing your in-class time by putting in hours at home–there’s no way around it. Think of yourself as a pilot, needing to clock a certain amount of airtime in order to become qualified. In order to reap the rewards of your knee replacement and be a “qualified knee recipient” you’ve got to put in the hours to improve your motion.

A well-rounded ReHab program includes daily exercises like heel slides and single leg stances, gets you up and moving, and encourages lifestyle changes that promote better healing.

Track Progress Regularly

Having your flexion measured weekly by your physical therapist doesn’t keep you in check enough. Like hopping on the scale frequently during a weight loss program, measuring your flexion regularly helps to keep your eye on the prize. There’s something to be said about being able to check-in on your goal more regularly, on your own time. This give you the opportunity to celebrate small wins or catch yourself slipping, and feel encouraged to up your game.

With this, the PeerWell app has an exciting announcement!

Measure ROM at Home

ROM basics

For the first time ever, you can measure your range of motion at home! Use the PeerWell on your smartphone or handheld device to measure your ROM without waiting for your physical therapist. PeerWell is proud to bring this innovative technology to our app users, to better track their progress and ReHab success.

Are you thinking about a hip or knee replacement? Get matched with a top orthopaedic surgeon near you who offers PeerWell PreHab and ReHab for free. PreHab gets you mentally, physically and environmentally prepared for surgery, putting YOU to greater control your outcome and recovery.

Dr. Nicholas Frisch, M.D., OS, MBA is an award-winning orthopedic surgeon based out of Rochester, Michigan. He focuses on minimally invasive joint replacement surgery and complex revisions. Dr. Frisch completed his residency at Henry Ford Hospital in Detroit and his Adult Reconstruction Fellowship at Rush University Medical Center in Chicago. Dr. Frisch is has won Orthopedics Best Clinical Article Award, the AAHKS Healthcare Policy Fellowship, Outstanding Resident Award Henry Ford Hospital, the Ford Motor Co. Connected Health Challenge, and more.

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