Ice After Total Knee Replacement: A PT’s Complete Guide.

An almost universal problem my total knee replacement patients have, when I see them in their homes a day or two after surgery, is the incorrect instructions they have received on the use of ice packs and the incorrect size of the ice pack they have been provided after surgery for their use at home.

The ice packs the patients are receiving are totally inadequate. They do not have the size and bulk that an ice pack needs to be effective at reducing pain and swelling after a total knee replacement surgery.

Along the way, the patient has invariably been instructed to ice the knee for 15 to 20 minutes, remove the ice pack for 20–30 minutes, then re-apply the ice pack to the knee again for another 15-20 minutes.


So let’s talk about the RIGHT way to use cold therapy after a total knee replacement surgery.

What is the best way to apply cold therapy after total knee surgery?

  • The best way to apply cold therapy after total knee surgery is by using a Cold Therapy Machine.
  • The 2nd best way to apply cold therapy is by using commercial cold packs.
  • A 3rd alternative is by making your own cold packs from frozen vegetables

Cold Therapy Machine

Electing to use a cold therapy machine eliminates the possibility of causing frostbite and decreases the attention required to change cold packs every hour or to replenish the ice every 4-6 hours in the cold therapy machine.

A cold therapy machine is basically a six-pack insulated cooler with a submersible pump that pumps cold water through attached exterior outflow/inflow lines to continually circulate cold water.

One of several differently designed pads is attached to these lines.
Cold water circulates through a network of small water lines embedded in the pad to control the knee swelling and pain.

The pad is placed on the new total knee replacement surgical site with a thin layer of insulation between the pad and the knee. That insulation could be as thin as a pillowcase or as thick as a hand towel.

The instructions with the cold therapy machine state to fill the unit with ice and then add water up to the line that is marked “water line” inside the cold therapy machine.

There is not any refrigerator whose ice maker can keep up with the demand to keep the cold therapy machine operational, so patients need to make a daily run to the store to buy big bags of ice.

Replenishing the ice is a sloppy, floor-wetting task that is aggravating to the caregiver and a slipping danger for the patient.

The solution is to use bottled water (a size that will fit into the cold therapy machine) that has been frozen in the freezer. No more fuss or muss, simply wipe the water bottles dry when removing them and replace them with new frozen bottles of water (and put the removed bottles back into the freezer for re-use).

There will be a need for two sets of bottles to rotate into the cold therapy machine. A set of frozen bottles in the cold therapy machine will last for about 6 hours. That is plenty of time for the previously used bottles to re-freeze.

All cold therapy machines are not created equal.

Before buying my own cold therapy machine I spoke to a durable medical equipment vendor that rents cold therapy machines to patients after surgery. They chose a machine for their rentals that has the best life expectancy and the least amount of problems.

That is the machine I purchased for my family’s own personal use.
The trademark is Cold Rush by Ossur, (Amazon link).

The Cold Rush by Ossur system can be purchased without a pad but is unusable without a pad.
I prefer the “Universal Pad” for my total knee patients, and that is the pad I also purchased.

The Cold Rush Ossur unit can accommodate 5 water bottles of the 16.9oz standard size I purchase from Costco.

Ossur Cold Therapy Unit with water bottles
Kirkland water bottle

Commercial Cold Packs

Commercial cold packs are another, less expensive way of controlling the pain and swelling after a total knee replacement surgery, but these cold therapy packs carry the possibility of frostbiting the patient.

Size makes a difference!

My patients are never sent home from the hospital with any type of cold pack that has the size or flexibility needed to adequately control pain and swelling.

One would think that after a very expensive surgery, the insurance carriers would not cheap-out on a $12 cold pack, but they do!

The correct size cold pack to adequately service a total knee surgery is a gel pack measuring 10” x 13”.

This size will cover the entire front and sides of the knee from above the surgical site to below the surgical site.
It MUST be a moldable gel pack so the top and both sides of the knee are in contact with the cold pack.

The cold packs I personally use and suggest to my patients are cold packs made by Core Products, an affiliate link.
I suggest buying two, which will allow you to rotate them and always have a cold pack ready to use.
They are very durable; I have cold packs that have lasted years.

Cold gel packs can’t be placed on bare skin, they will frostbite the flesh!

Here is a picture of a friend of mine who placed the cold pack directly on the skin of his lower back, and when he took the cold pack off, the skin came off with the cold pack.

This picture is 10 weeks after the frostbite. Notice the brown coloration around the primary spot, which indicates tissue damage as well.

2019 Steves Frostbite 10 weeks post 3 cropped and enhansed

Please remember, when these cold gel packs come out of the freezer, they are about 0 degrees Fahrenheit!

A simple layer of a clean, dry, thin hand towel can offer protection from frostbite, especially while the knee is bandaged and the knee cap has extra layers of protection from the bandage.

If the total knee replacement surgery has been closed with metal staples, I would recommend using extra layers of insulation between the cold pack and the knee.

Staples TKR cropped
Metal stapes will require more insulation from a cold pack coming out of a freezer

Homemade Frozen Vegetable Cold Packs

Some of my patients have been successful in making their own cold packs out of frozen vegetables.

Most often, I see my patients use this technique because they were discharged to home with inadequate cold therapy packs, and they resort to using frozen vegetables while they wait for their cold therapy machine or cold packs to arrive.

Things could have been so much easier for them had they only known they would need a cold therapy machine or cold gel packs BEFORE they had the surgery.
Pain and swelling just doesn’t wait for them to get ready after the fact.

So as they wait for a more permanent solution, they resort to frozen vegetables to get them through the interim.

Believe it or not, there is a “correct” frozen vegetable to choose to get the job done.

20230426 143358 scaled

Two-pound bags of frozen baby lima beans are the perfect vegetable cold pack.
They are just the right size to completely contact the knee.

Regular lima beans are too large and the gaps between the beans leave the knee with “hot spots”

Smaller vegetables thaw too quickly and become ineffective, requiring multiple packs to make it through the amount of time the knee needs to be cooled at one session.

My instructions to my patients using vegetable cold packs:

  • Buy eight 2-pound bags of baby lima beans.
  • Place two of the 2-pound bags in a pillowcase and drape them over a knee that is insulated with a thin hand towel.
  • Start by placing one edge of the pack on the bed at the inside of the knee, and wrap the beans over the knee to include the outside of the knee also.
  • Secure the entire pack by tucking the tail of the pillowcase under the knee.
  • Change the pack out after 30 minutes with a new lima bean cold pack to get an hour’s worth of cold therapy.
  • The remaining 4 bags of baby lima beans are held in the freezer to be used at the next icing session, allowing the previously used beans to freeze solid again.

How much can a total knee surgery patient use cold therapy?

A patient cannot use cold therapy too much after total knee surgery if the knee is adequately protected from frostbite.
Patients can, however, use cold therapy for too short a period of time in one session.
Removing the cold pack too soon can cause additional swelling.

After a total knee replacement surgery, cold therapy is the patient’s best friend.

Unfortunately, most total knee patients have been instructed to put cold packs on the knee for 15-20 minutes, remove the cold pack for 20-30 minutes, and reapply in this manner repeatedly.

This cold therapy on-off-type application technique is great if one is trying to do a blood-flush on a sore and achy muscle, but following this technique with a new total knee replacement can cause additional swelling, resulting in increased pain.

Let me explain:

If I place a cold pack on the back of my hand, the first thing my body will do is stop sending as much blood down to that hand as normal. The body shuts down the blood flow to the hand to protect the body’s core temperature.

If I take that cold pack off my hand in say about 20 minutes, the brain says “We like that hand, so let’s send a bunch of blood down to that hand to warm it back up”.

I don’t want a “bunch of blood” being sent to my patient’s knee.
That “bunch of blood” carries a lot of fluid with it and increases the swelling in the knee.

If I leave that cold pack on the back of my hand for 40 minutes or longer, when I remove the cold pack, the brain says “We like that hand, but we don’t trust that hand, so let’s warm it up SLOWLY”.

That is what I want for my patients.
The ability to control pain and swelling with cold therapy without adding any swelling.

I advise my patients to use cold therapy as much and as often as they want, but once the cold therapy is applied, do not remove it for at least 40 minutes.

Still a doubter?
Consider this:

Have you ever been watching a football game and in the first half a player injures his knee?

Then that same player comes out of the locker room for the second half, sits on the bench with his leg propped up with this HUGE ice pack on his knee.

He sits there for the entire second half of the game without ever even once removing that ice pack.

That’s because those highly qualified trainers (many are physical therapists) understand this “blood-rush” concept and they most certainly do not want that very valuable player’s knee to swell.

Unfortunately, many healthcare providers treating the regular public, understand the “blood-flush” technique but don’t understand cold therapy’s potential to cause swelling in a newly surgerized knee if the cold therapy is removed too quickly, hence the misinformation is given to the patient by doctors, nurses, and even hospital-based physical therapist.

Read my other articles about Total Knee Replacement

Wishing You A Pain-Controlled Recovery

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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