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As a physical therapist, having seen hundreds of total knee replacement patients a day or two after surgery, sleep disturbance is a common complaint.
Getting adequate sleep after a total knee replacement is a huge factor in the patent’s pain perception after total knee replacement
The total knee replacement patients I see in their home after total knee replacement are frequently telling me they did not sleep well the night before and I sometimes see this sleep disturbance pattern lasting for much longer than necessary.
After a couple of nights not sleeping well the patient will become increasingly irritable, desperate to get some sleep.
My experience, treating patients with sleep disturbance after total knee replacement, is that after about three nights of poor sleep, the sleep deprivation is as much of a problem for the patient than the pain that is keeping them awake.
All of my patients are using either Ice Packs or Cold Therapy Machines (Amazon affiliate links) multiple times daily to help control pain levels.
See my article: Ice After Total Knee Replacement: A PT’s Complete Guide.
Why does total knee replacement pain wake me at night?
The two most common reasons a new total knee patient’s pain wakes them in the middle of the night are:
- Their body is not producing enough endorphin and enkephalin to control the pain from about 2-3am until sunrise. It is released on a circadian rhythm.
- Poor knee sleeping posture.
Circadian Rhythm
Inside everyone’s brain, there is an internal 24-hour clock controlled by the hippocampus.
This circadian rhythm controls such things as the energy levels a person may have during different parts of the day.
The circadian rhythm can be influenced by external factors such as light and darkness.
An example would be when the eyes recognize it is dark outside and informs the hippocampus it is time to slow down a little. The hippocampus, upon receiving this information, signals the release of melatonin. The melatonin causes the person to become tired and readies the person for sleep.
That is what “jet lag” is all about. When the 24-hour cycle is interrupted by a period of significantly increased or decreased light such as a long plane trip, that person can experience difficulty with sleep and awake times sometimes taking several days to re-adjust to the current time zone.
Endorphins and Enkephalins
Endorphins and Enkephalins are two different five-amino-acid molecules produced by the human body and found distributed throughout the human body in the brain, nerve tissue, and some endocrine glands.
They are the body’s own pain killers and anti-inflammatory hormones.
Endorphins and enkephalins are produced by the human body on a circadian rhythm.
They are released at sunrise and enough is produced to last four about 20 hours on a kind of time-release schedule.
That means at about 4 hours before sunrise the body starts to burn through its supply of endorphins and enkephalins leaving the patient without their natural pain killers at about 2-3 o’clock in the morning.
And that is what my patients tell me as well as experiencing the same thing myself.
We go to bed and about 2-3am we are awakened by pain.
I have, on more than one occasion, been awakened at 2-3 in the morning with pretty severe pain. I have sat at my kitchen table wringing my hands trying not to give in to taking more pain medication, and at sunrise, I get a significant reduction in pain, enough so that I can go back to bed and sleep till about 10 am. Upon awakening, my pain levels are tolerable even without pain medication.
My experience has always been in regard to lumbar flare-ups from having considerable joint and disc degeneration, not a surgical procedure, so I had not been taking prescription pain medications before the lumbar flare-up, I really try to avoid them if I can.
But my experience translates perfectly to the physiology of endorphins and enkephalins, as well as matching the pattern of my patient’s symptoms of pain.
So I took this information and experience and came up with my own intervention philosophy to break that 2-3 am pain increase.
I suggest to my patients that are experiencing this pain increase in the middle of the night to put off that last dose of pain medications until midnight or after.
The pain medications usually have an effective time frame from 4 to 6 hours after taking the medication. Delaying the last pain medication intake until after midnight should carry the patient through that 3-4 hour window of decreased or absent endorphins and enkephalins.
All the patients that have followed this advice of taking the last medications at midnight or later have reported they were able to sleep through the night without pain waking them.
One thing to keep in mind is that the patients I am discussing here are new total knee recipients and almost 100% of the patients I have seen are taking opioids to control their knee pain. These are patients that are no more than 3-4 weeks out from their surgery date.
Night pain can be a sign of more sinister pathology and if severe or prolonged needs to be evaluated by the surgeon.
A study Circadian Rhythms, Sleep, and Substance Abuse state substance abuse can cause a disturbance in the circadian release of endorphins and enkephalins making the patient even more vulnerable to night pain.
While the new total knee recipient taking opioids after their surgery certainly are not substance abusers, they are in fact taking the drugs that are most commonly abused, therefore it makes sense to me that the pain medication is both suppressing the patient’s body to produce its own painkillers and anti-inflammatories, it also can interfere with sleep just by itself.
And sadly, many of my patients were taking opioids prior to the surgery to control pain and improve mobility. Some for months.
See my article on pain control after Total Knee Replacement surgery…..
Poor Sleep Posture
After a total knee replacement surgery all my patients sleep on their back, or on one side or the other. I have never seen a total knee replacement patient that could sleep on their stomach, at least not initially.
Each of these positions has the potential to increase the patient’s knee pain at night, but for different reasons with different intervention solutions.
Sleeping On Your Back
Most of my total knee replacement recipients are sleeping on their back, at least for the first few days after surgery.
The patients that are having trouble with that position (because of breathing or other issues) usually tell me they are sleeping in their recliner chair.
Sleeping in a recliner chair is a great solution for a few days, but after a while, even with the recliner chair tilted back all the way, the amount of weight that is put on the tail-bone (coccyx) becomes uncomfortable and most of my patients transition back into bed with a side-lying posture.
Sleeping on the back puts the operated leg into full available extension and many patients without full extension range of motion find this position generates too much pain in the knee.
This is because the knee will not come out straight allowing the back of the knee to be supported by the bed.
It’s kind of like leaning on the wall with the hand in extension, initially it feels fine but after a while the wrist begins to complain because of the stretching that is happening to the wrist in this position.
Frequently my patients are using a pillow under their knee to support the knee to get rid of that stretching pain.
I discourage the use of a pillow under the knee in bed or in the recliner chair. While this position is comfortable for the patient, it is counterproductive to gaining full extension range of motion.
Extension range of motion has a window of about 6-8 weeks for achieving full extension range of motion. After that time frame, it becomes much more difficult to get full extension.
At that stage of rehabilitation, the surgeon will be thinking about taking the patient back to the operating room and, under anesthesia,, manually manipulate the knee to break up the scar tissue that is forming.
My patients are encouraged to sleep on their back without a pillow under their knee, and if that position becomes uncomfortable, switch to a side-lying position instead of stuffing a pillow under the knee.
Sleeping Side-Lying On The Unoperated Side
This seems to be the most comfortable for my total knee patients if they are properly supporting the operated leg.
Most patients have heard that putting a pillow between their legs when sleeping side-lying is the correct way to sleep on the unoperated side, and they would be correct.
However, most of my patients are using the wrong pillow size the first time I see them.
They are sleeping on the unoperated side with a REGULAR SIZED PILLOW between their knees.
Since the pillow does not support the foot and ankle (and sometimes up to mid-calf), the pillow creates a fulcrum over the knee, and the foot/ankle weight is trying to bend the knee side-ways.
The correct way to sleep on the unoperated side is to use a body pillow (like a pregnancy pillow). The bottom of the pillow should extend past the foot and ankle as the patient rests their leg on the pillow.
This pillow support needs to extend up the leg to the groin area at the hip. Most body pillows will extend up further than the groin.
This technique of full support of the operated leg completely eliminates any lateral stress on the knee.
My patients often modify this position by placing the body pillow slightly in front of the bottom leg, then slightly flexing at the hip and resting the operated leg on the pillow fully supported.
If a body pillow is not an option, the patient can use multiple regular pillows to achieve the same positioning, but the pillows tend to separate over time.
Wrapping the pillows in a sheet and binding them into a solid unit is advisable.
Sleeping Side-Lying On The Operated Side
The biggest problems my total knee patients have sleeping on the operated knee side is usually the “contact pain” from the mattress or from the unoperated leg.
The outside of the knee can be sore and sensitive enough that even its own weight against the mattress causes increased pain. Relieving the weight on the knee can be reduced by using a body pillow to prop the unoperated leg positioned in front of the operated leg can help.
The other, more common complaint I hear from my patients, is that when they are sleeping side-lying operated leg down, the top leg knee rests on the operated knee and causes pain.
Again, using a body pillow to position the top leg forward so the knees do not touch is the best solution.
Wishing You A Restful Full Night’s Sleep
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See My Related Total Knee Articles For Additional Information:
Best Exercises To PREPARE For Total Knee Surgery
Precautions After Total Knee Surgery: (Immediate and life-long)
TENS After Total Knee Surgery: (A PT’s Settings & Pad Placement)
Showering After a Total Knee Replacement: An OT’s Recommendations
A PT’s Total Knee Pain Expectations; (Day 1 through Day 30)
Total Knee Replacement Manipulation: (When & Why To Consider)
Total Knee Replacement Outcomes After Home Physical Therapy
Pain Control After Total Knee Surgery: (A Complete Guide)
Walking: The Perfect Exercise After Knee Replacement
Walking After A Total Knee Replacement: (When and How Much?)
Knee Pain After Total Knee Surgery: A Physical Therapist’s View
Ice After Total Knee Replacement: A PT’s Complete Guide
Paying It Forward
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