Total Knee Replacement Manipulation: (When & Why To Consider)

In the past 10 years of seeing patients in their homes and starting their home physical therapy recovery process, I can say that I have seen fewer than 5 patients that require manipulation under anesthesia to regain range of motion after a total knee replacement.

One thing I can say, of the patients I have seen after total knee replacement surgery, people over 65 years of age do better than people under 65 years of age. The two studies I will cite later in this article seems to validate my observation.

That “older people do better than younger people” observation applies to both range of motion and pain levels. I really don’t have an answer for that observation, it seems backwards to me, but that is certainly my observation after seeing hundreds, if not thousands, of total knee patients.

Tip 1: Apply Cold Therapy Before Going To Bed.

All of my total knee surgery patients are using either Ice Packs or Cold Therapy Machines (Amazon affiliate links) multiple times daily to help control pain levels. Applying cold therapy for 40 minutes just before going to bed will reduce your pain while sleeping
See my article: Ice After Total Knee Replacement: A PT’s Complete Guide.

What is Manipulation After a Total Knee Replacement?

  • “Manipulation” of a total knee refers to a medical procedure called MUA or manipulation under anesthesia.
  • The patient is placed under a general anesthetic, and once “out”, the surgeon applies a progressive loading manual force in extension and/or flexion to break scar tissue.

Is Total Knee manipulation an Outpatient Procedure?

A total knee replacement manipulation to gain extension and/or flexion does not require being admitted to a hospital, however, the manipulation will be done under general anesthesia either in a hospital or outpatient surgical center.

If the total knee surgeon is located in a fair-sized city and is doing a lot of total knee replacements, there is a high likelihood that the surgeon will be using an outpatient surgical center instead of the hospital’s operating room.

When Will an MD Consider Extension Manipulation of a Total Knee?

  • A surgeon will start thinking about manipulating a total knee at about 3 weeks after surgery if the extension is 10 degrees or more short of full extension.
  • The actual manipulation would usually take place between 6 and 12 weeks post-surgery

Extension (getting the knee out straight) is “special” after a total knee replacement surgery!

There is a window of opportunity to gain full extension of the knee but that window of opportunity starts to quickly close at about 6 weeks.

After about 8 weeks post-surgery, if the knee is still more than 10 degrees short of extension, the therapist has a near-impossible task of getting that knee out straight without the surgeon’s help of manipulating the knee under anesthesia to break that scar tissue.

Why is Getting the Knee Out Straight Important After Replacement Surgery?

  • Walking on a “bent” total knee, 10 degrees or more, causes body weight transfer to the ground in a straight line to be altered.
  • This altered line of weight transfer to the ground produces a “shear” force at the knee causing excess stress and wearing them out faster.

The normal life expectancy of the total knee recipients I see is being told the new total knee should last them for 30 years or longer, even with an active lifestyle.

When Will an MD Consider Flexion Manipulation of a Total Knee?

The Surgeon will start considering total knee manipulation for flexion if:

  • It is about 8 weeks or more post-surgery.
  • The knee has less than 90 degrees of flexion.
  • Outpatient physical therapy series of treatments have failed to gain the desired flexion.

Flexion range of motion is much more “time-forgiving” than extension, and my personal experience has been that I can gain more flexion in a patient’s total knee, even at 3 months post-surgery, although FULL flexion may require manipulation under anesthesia.

Full range of flexion motion is not required to have a full functional range of motion.

Full range of motion of the knee is not usually limited by the knee joint itself, the limitation is the calf muscles hitting the hamstring muscle.

What is Full Functional Flexion After a Total Knee Replacement?

A total knee replacement patient needs 110 degrees of flexion to be able to:

  • Drive or ride in a car for longer than an hour.
  • Sit at a dinner table for longer than an hour.
  • Come DOWN stairs step-over-step instead of one step at a time.

What are the Range of Motion Expectations After Manipulating a Total Knee?

A study in US National Library of Medicine reported these results after total knee manipulation:

  • ROM prior to manipulation was 10.04 degrees of extension to 71.2 degrees of flexion.
  • ROM after manipulation improved to 2.1 degrees of extension to 91.9 degrees of flexion, an improvement of 79.8% of knee extension and a 29.07% improvement of flexion.

Three months post manipulation, the ROM the average patient was able to maintain was about 98% of the range of motion that was gained with the manipulation under anesthetic.
Read this study from US National Library of Medicine here…..

What Percentage of Total Knees Undergo Manipulation?

According to a study in The Journal of Arthroplasty, on average only 3.59% of 1,729 patients studied required a total knee manipulation.
Read this study from The Journal of Arthroplasty here…..

What Increases the Risk of Requiring Total Knee Manipulation?

According to a study in The Journal of Arthroplasty, increased risk of a total knee needing a manipulation include:

  • Patient is younger than 65 years old.
  • Patient is a smoker.
  • Patient has had a prior surgical procedure before the total knee replacement.

The study looked at 1,729 total knee replacement patients who had undergone knee manipulation after the surgery.

Of those 62 patients who had their total knee manipulated after surgery, the average age of the patient was 55.2 years old.

The average age of all 1,729 patients was 65.3 years old.
Read this study from The Journal of Arthroplasty here…..

How is Manipulation After Total Knee Replacement Performed?

After placing the patient under general anesthesia or a spinal block, the surgeon applies a steady, progressive manual pressure until the surgeon hears and feels an audible “pop” produced by the breaking of the restrictive scar tissue.

No further force is applied after the initial breaking of the scar tissue.

What is the Total Knee Replacement Post-Manipulation Protocol?

  • Prescription or continuation of pain medication.
  • Home cold application with cold packs, or preferably, a cold therapy machine to control swelling.
  • Home Continuous Passive Motion machine (CPM).
  • Re-initiate outpatient physical therapy.


Pain medications come with their own problems, such as addiction after a period of time and a decrease in gut motility that frequently causes constipation.

Cold application

Cold will be the manipulated patient’s friend. It holds swelling down, and swelling is the primary pain generator.

Cold can not be used too much, but it can be used for too short a period of time.
Cold removal before 40 minutes of use can increase the swelling because of the blood rush the knee receives when removing the cold sooner than 40 minutes.
Read my article: Pain Control After Total Knee Surgery: A Complete Guide…..

Continuous Passive Motion machine (CPM)

Continuous passive motion machines are intended to maintain the range of motion gained with the manipulation, not stretch the knee for a further range of motion.

Using a CPM is time-consuming. Most surgeons ordering CPM after a knee manipulation are asking their patients to be in the CPM for two hours at a session and repeat that two-hour treatment two or three times a day

Re-initiate outpatient physical therapy

Outpatient physical therapy will also be focused on decreasing pain and swelling after the manipulation as well as maintaining and gaining more range of motion.

Final Thoughts

Although during the first 2-3 weeks of home physical therapy, the therapist will not be manually pushing the knee or assisting the patient manually to achieve greater ROM, they will be encouraging the patient to do as much self-stretching as the patient can tolerate, respecting the rule of no increased prolonged pain after self-stretching.

The more ROM that can be gained in the first 2-3 weeks, the less likely the patient’s surgeon will even consider manipulation.

Read my other articles about Total Knee Replacement

Paying It Forward

Perhaps you are approaching or already retired and wondering how you could earn extra money in retirement.
One option would be to do as I am doing.
Read my article How To Generate Retirement Income: Cash In On Your Knowledge.

Dr. Robert Donaldson

Dr. Donaldson is dually licensed; physical therapy in 1975 and doctor of chiropractic in 1995. He held credentials of Orthopedic Clinical Specialist in physical therapy for 20 years, QME in California, and taught at USC. He owns and operates an orthopedic physical therapy practice. See "About Me" page.

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