Sleeping Position After Hip Replacement: Lying on the Back, Side Sleeping With a Pillow and the First Six Weeks

After a total hip replacement and returning home, how should you sleep on the first night? Is sleeping on the side allowed, or must you lie flat on your back all night? In home assessments almost every patient asks this question. When awake in the daytime you can keep reminding yourself not to cross your legs, but once asleep you can no longer control it.

In short: in the early period lie on your back, or lie on the non-operated side with a pillow between the legs to keep the hip abducted. After a posterolateral approach, do not turn toward the operated side in the first six weeks or so, and also avoid hip flexion beyond 90 degrees, adduction across the midline and internal rotation. Many studies indicate that relaxing the restrictions does not raise the dislocation rate, but the advice mostly comes from clinical practice and not from high-quality clinical trials (the Cochrane review by Smith 2016 rated the certainty of the evidence as very low). How strictly the restrictions are applied therefore still depends on the patient’s surgical approach and the instructions of the treating team. The sections below explain the reasons, the specific methods and the timing of relaxing the restrictions, one at a time.

Sleeping position in the early period after surgery: points for lying on the back and the side

The safest default sleeping position is on the back (lying flat). In this position the operated hip rests naturally in a neutral position and is not pulled into adduction or internal rotation by its own weight. The StatPearls guidance on hip precautions (Deak & Varacallo) advises lying mainly on the back for about the first six weeks after surgery, and not lying on the non-operated side. The reason is that when lying on the operated side, or on the side without a pillow, the upper leg easily drops across the midline of the body. If the patient is used to sleeping on the side and cannot sleep lying flat, the patient should turn toward the non-operated side and put a sufficiently thick pillow between the thighs to support the upper operated leg and keep the legs apart.

What a pillow between the legs does

A pillow between the legs has a clear mechanical basis. The direction in which an artificial hip (especially after a posterolateral approach) most easily dislocates is when adduction, internal rotation and excessive flexion happen together. When the operated leg crosses the midline of the body while turning inward, the head of the femur is pushed backward against the weakened posterior capsule. The pillow fills the gap between the legs with a solid object, so that even when the patient turns over in deep sleep, the legs cannot come together or fall across the midline. No one can control their sleeping position by willpower all night, but a physical barrier can be set up in advance that cannot be crossed in deep sleep.

The principle of “maintaining abduction” has a biomechanical basis. A computer simulation study (Eslam Pour 2023) found that, with a large femoral head and proper positioning of the acetabular cup, maintaining about 20 degrees of hip abduction alone is enough to prevent joint impingement during flexion, and the reduction in impingement risk when bending forward can reach 0 to 16.3%. In other words, the abduction angle held open by a pillow has a reasonable mechanism of its own for reducing impingement and so lowering the risk of dislocation. Why “flexion beyond 90 degrees” and “internal rotation” are also high-risk movements, and how the different surgical approaches differ, is covered in the page on hip precautions and dislocation risk after hip replacement.

Steps and points for getting into bed, turning over and getting out of bed

A safe sleeping position is more than the position once lying down. The three transitions of getting into bed, turning over and getting out of bed are often more critical. Clinically, dislocation usually does not happen during deep sleep, but when twisting toward the edge of the bed to reach for something while half asleep, or in the moment of getting out of bed in a hurry. The practical points for each movement are below.

Safe ways to handle the three transitions at night:

• Turn the whole body together—When turning over, the shoulders, pelvis and legs should turn together like a log (log-roll). Never twist only at the waist or turn the pelvis to reach for something at the bedside, or the operated hip may be pulled toward the midline of the body.
• The pillow turns with the body—If you want to turn to the other side when sleeping on your side, first sit up, set the pillow in its new position and then lie down again. Never lie there and drag the legs over to the other side.
• Get out of bed on the non-operated side—When getting out of bed, you should generally turn first toward the non-operated side, move both legs to the edge of the bed together, and then push up with both hands on the bed to sit up. This reduces twisting force on the operated hip alone. Which side to get out on depends on the position of the surgical incision, and it is best to ask the therapist to demonstrate it in person before discharge.
• Sit still for a moment before standing—When getting out of bed, sit steadily at the edge of the bed for a moment before standing up. This lowers the risk of dizziness and falling from postural low blood pressure, which matters especially in the early period after surgery.

Some research has looked specifically at whether patients can actually keep to these sleeping position restrictions. A randomised controlled trial (Peters 2022) found that among patients after a posterolateral approach who were told to sleep on their backs, 81% complied with lying on the back in the first two weeks after surgery. Removing this sleeping position restriction, however, markedly reduced the psychological and physical burden on patients, and did not affect their compliance with other protective measures. This shows that sleeping position restrictions are a source of stress for many people, and patients may wish to discuss in detail with the therapist which rules must be followed strictly and which can be relaxed to a reasonable degree. To extend these safety principles to high-risk daily movements on wet floors such as bathing and getting in and out of the bath, see the page on safe bathing and showering after hip replacement.

When the sleeping position restrictions can be relaxed

These sleeping position restrictions are not lifelong rules. Traditionally about six weeks is used as the dividing line, giving the soft tissue around the hip time to heal at first. In recent years a growing body of research has shown that relaxing or even removing these protective measures does not raise the dislocation rate. It must be noted, however, that “evidence shows relaxing is no worse than strict compliance” does not mean that the patient can ignore the precautions altogether from the first day.

This point needs to be made clear: what the studies above compare is that the effect of relaxing the restrictions is no worse than strict compliance, and they do not prove that “the restrictions do nothing and can be ignored altogether”. In addition, the overall quality of the evidence in these studies is low. The Cochrane review (Smith 2016) included only 3 small trials, covering 492 participants and 530 total hip replacements, with its GRADE certainty rated very low, and its conclusion was only that “the existing evidence is not enough to support or oppose” such protective programmes. Whether to relax the restrictions is therefore a matter of clinical professional judgement more than of following a fixed deadline, and the safest approach is always to follow the timetable set by the treating medical team.

Differences in the high-risk directions for the posterolateral and anterior approaches

One key point is often overlooked: for different surgical approaches, the sleeping directions to avoid are in fact opposite. What the posterolateral approach most needs to avoid is flexion, adduction and internal rotation (which easily cause backward dislocation), so a pillow while sleeping on the side and avoiding turning toward the operated side are especially important. With the anterior approach, on the other hand, the high-risk direction is broadly extension together with external rotation, and side sleeping is sometimes less restricted. For this reason, claims passed on by word of mouth among friends and family, such as “after a hip replacement you must never sleep like this”, do not necessarily apply to every patient. Patients must follow strictly the instructions given by the treating surgeon and physiotherapist for the individual surgical approach, and must not copy one general rule blindly.

How the Hong Kong home environment affects sleeping position

In the cases seen at home assessments, the most common trap is often not that the patient forgets to “turn toward the non-operated side”, but that the way the bed is placed forces the patient to turn toward the operated side without anyone noticing. Beds in Hong Kong homes are generally low, and most have one or three sides against the wall. When turning in deep sleep, the patient easily brings the legs together toward the wall side without realising it, and the wall side may well be the operated side. In practice, the therapist will suggest arranging the bed so that the operated side faces the centre of the room (the outer side), and putting a firm long pillow or body pillow between the legs, never a soft pillow that flattens easily, which loses its support. In subdivided flats and old tenement buildings the bedrooms are also narrow, and getting out of bed often means pushing up sideways, which can easily cause hip adduction and twisting in an instant. A safer way is to put the non-operated foot down first when getting out of bed, keep the whole body turning together and avoid twisting at the waist, and to place a stable low stool beside the bed for support.

Why do these two points need the therapist to come to the home in person? The reason is that deep sleep at night is the time the patient has least conscious control, and also a time when the risk of dislocation is relatively high. A pillow between the legs turns the principle of “maintaining abduction” into a physical barrier that makes it hard for the legs to come in and cross the midline even when turning over in sleep. The point is not to ask the patient to lie stiffly all night (which is simply impossible in reality), but to set a line of protection beforehand that cannot be gone around in deep sleep. When the home-visiting therapist comes, the therapist measures the height of the bed, how it is placed and which side is against the wall, and from this decides which direction the operated side should face when sleeping, and does not rely only on telling the patient “remember to turn toward the non-operated side”. The actual layout of the home often forces the patient to turn toward the operated side without anyone noticing, and such traps in the environment are hard to spot when explained in a hospital or clinic. To plan sitting, using the toilet and dressing beyond sleeping position as well, see the overview of daily movements and aids after hip replacement, where the five daily scenes are covered in one place.

When to ask a physiotherapist for help

After returning home, if the bed placed against the wall forces you to turn toward the operated side, if you cannot keep the pillow in place when sleeping on your side, or if getting out of bed hurts so much that you are afraid to move, do not just put up with it, and there is no need to lie awake worrying all night. These are exactly the signals that call for a home assessment. The home physiotherapy provided by Nova Health’s registered physiotherapists visits the patient’s home to measure the height and placement of the bed, plan which way the operated side faces when sleeping, and demonstrate the log-roll technique and the steps for getting out of bed on the spot, putting the abstract sleeping position protection principles into the real living environment. If the patient has persistent severe pain, the affected leg suddenly looks clearly shorter or turned outward, fever, or a red, swollen or oozing wound, however, the treating orthopaedic team should be contacted as soon as possible for follow-up.

Frequently asked questions