When Can You Cross Your Legs, Bend Past 90 Degrees or Sleep on the Operated Side After a Hip Replacement?

After a total hip replacement, the three questions families ask most often are about three everyday movements. When can the legs be crossed? Can the patient bend to pick things up, or sit on a low stool so the joint bends past 90 degrees? Can the patient sleep on the side that was operated on? These three ordinary postures are exactly the directions of movement that a posterolateral approach hip replacement most needs to avoid.

Traditionally, the rules of no leg crossing, no bending past 90 degrees and no sleeping on the operated side are relaxed about 6 to 12 weeks after a hip replacement, because this is when the soft tissue after a posterolateral approach is at its most fragile in healing. In recent years, however, several randomised controlled trials have confirmed that relaxing restrictions does not raise the dislocation rate. When to relax them should be assessed for the individual by the surgeon according to the surgical approach and the stability of the joint during the operation (Tetreault 2020; Korfitsen 2023). The sections below go through the timeline for lifting restrictions on each of these three movements and the reasons behind it.

Why leg crossing, bending and sleeping on the operated side are avoided

The posterolateral approach (posterior approach) enters through the back of the buttock, and during the operation the capsule and external rotator muscles at the back of the hip joint are cut and repaired. With this approach, the posture most likely to cause dislocation is the moment when flexion, adduction and internal rotation all occur at once. A single angle may not be a problem, and it is the combined movement that is the real danger. Crossing the legs makes adduction and internal rotation together. Bending past 90 degrees is a large flexion. Lying on the operated side makes the upper thigh adduct across the midline. Each of the three movements touches one part of this high-risk posture.

How these three movements form the high-risk combination

Crossing the legs: the thigh on the operated side crosses the midline of the body (adduction) and turns inwards (internal rotation) at the same time
Bending over or sitting on a low stool: the hip is flexed beyond 90 degrees
Lying on the operated side: the upper thigh, or the thigh on the operated side, adducts inwards across the midline of the body

Movement angles advised by the Hong Kong College of Orthopaedic Surgeons

In the first 8 weeks after surgery, forward flexion should not exceed 60 degrees
After that, forward flexion should not exceed 90 degrees
Avoid turning the thigh inwards and crossing the feet, and when lying on the side a pillow must be kept between the legs

The patient information of the Department of Orthopaedics and Traumatology at the University of Hong Kong gives the same advice: the recovery period after surgery is generally 6 weeks to 3 months, during which combined movements of flexion, adduction and internal rotation should be avoided, and flexion should usually not exceed 90 degrees, although the exact limit still depends on the stability of the joint at surgery. To understand more about the biomechanics behind these three angles, see the overview of hip precautions and the risk of dislocation.

The 6 to 12 weeks of soft tissue healing after surgery

Most restrictions after surgery are concentrated in the first 6 to 12 weeks. This is not an arbitrary time limit. It depends on how far the capsule and external rotator muscles at the back have healed. During this period the repaired soft tissue is not yet fully strong, so the risk of dislocation is also concentrated in it.

0 to 6 weeks after surgery: the most conservativeIn the early period, the repaired soft tissue at the back is still fragile, and crossing the legs, bending too far and lying on the operated side should all be avoided. When lying flat, a pillow is also kept between the legs to keep the legs apart.

About 6 to 12 weeks: relaxing step by stepAs the soft tissue heals more and more firmly, most doctors, once the joint is confirmed stable at follow-up, relax the restrictions one by one according to the individual patient. They are not lifted automatically after a set number of days.

The doctor decides when to relaxWhen exactly restrictions can be relaxed depends on the surgical approach, the stability during the operation and the imaging results, and the patient should not judge it alone or try early.

This healing period has clinical data to support it. A study of 841 cases followed for over 10 years found that the technique of repairing the posterior capsule directly affects the early dislocation rate: the group in which the capsule was sutured to the greater trochanter recorded 22 dislocations, whereas the group that used side-to-side suturing recorded 0. Dislocation risk also rises with the patient’s age (OR 1.04 for each year; Hernandez 2020). In other words, joint stability early after surgery is closely tied to how complete the soft tissue repair is, which explains why careful protection is needed in the first weeks after surgery.

Clinical evidence on relaxing restrictions and the dislocation rate

Over the past ten years, several high-quality clinical trials have looked directly at whether relaxing restrictions after surgery raises the risk of dislocation, and their conclusions are quite consistent: provided the surgical repair is good, relaxing restrictions does not raise the dislocation rate.

Traditional strict restriction group

Tetreault 2020 prospective trial: dislocation 1.03%
Dietz 2019 multicentre trial: dislocation 1.3% (2 cases)
Crompton 2020 systematic review: dislocation 2.2%
Peters 2019 with sleeping position restricted: dislocation 1.48% (3 cases)

Relaxed or unrestricted group

Tetreault 2020: dislocation 0.68%, with earlier return to driving
Dietz 2019: dislocation 0.7% (1 case), P=.62, no difference
Crompton 2020: dislocation 2.0%, with no difference in confidence in function
Peters 2019 with sleeping position relaxed: dislocation 1.46% (3 cases)

Putting the data together makes the picture clearer. van der Weegen 2016 combined 6 studies with 1,122 operations: the restricted group recorded 8 dislocations (1.5%) and the unrestricted group 6 (1.0%). Korfitsen 2023 combined 9 studies with 8,835 people and concluded that the early dislocation rate of the two groups “may show no difference or only a very small one”, and that the current evidence is not enough to support routine hip precautions after surgery. A systematic review on the anterolateral approach likewise reached the same conclusion: neither of the two eligible studies showed that movement restrictions help to prevent dislocation, and instead pointed out that restrictions were linked to slower recovery and lower patient satisfaction (Barnsley 2015). It must be noted that all these conclusions assume that the repair at surgery was good, and they do not mean that protective measures can be ignored altogether in any circumstance.

Points to note on crossing the legs, bending and sleeping on the side

The following is the general direction of the timeline, and the actual time to relax depends on the surgeon’s instructions at follow-up.

Crossing the legs—Traditionally, it is advised to avoid crossing the legs for at least the first 6 weeks (extended to 8 to 12 weeks in some cases), because this movement makes the hip adduct and rotate inwards at the same time. After the healing period, once the joint is confirmed stable at follow-up, most patients can relax step by step (HKCOS; Tetreault 2020).
Bending or sitting on a low stool past 90 degrees—In the first 8 weeks after surgery, forward flexion should not exceed 60 degrees and afterwards should not exceed 90 degrees. Take particular care never to twist the body while bending to pick something up from the floor. In daily life, a long-handled reacher and a high stool are advised (HKCOS).
Sleeping on the operated side—In the early period after surgery it is best to lie flat, with a pillow between the legs to keep them apart. When lying on the side, a pillow must also be placed between the legs to stop the upper thigh going inwards across the midline of the body. A non-inferiority trial shows that the dislocation rate after relaxing the sleeping position restrictions was no different from the traditional restrictions (Peters 2019).

The order and pace of relaxing the three restrictions of leg crossing, bending and side sleeping often differ from person to person. Some patients can return to sleeping on the side earlier, while crossing the legs has to wait longer.

Factors that affect when restrictions are relaxed

The clinical trend in recent years argues for individualised assessment and not a one size fits all rule. Patients with a low risk of dislocation and good joint stability during surgery can have restrictions relaxed earlier, while higher-risk people need a more conservative approach. When to relax should not be decided by a single factor or a fixed number of days, and the points below must be weighed together.

The main factors that affect the pace of relaxing restrictions: the surgical approach (the posterolateral approach puts more weight on restricting movements to the back), stability during the operation (the surgeon’s actual testing feel of the stability of the joint at the end of surgery), the technique of capsule repair, the patient’s age (Hernandez 2020 pointed out that the older the patient, the higher the early dislocation risk, OR 1.04 for each year of age), and the position of the prosthesis shown on medical imaging. All of these must be judged as a whole by the surgeon in charge, and the answer cannot be found by looking up a standard number of days.

The soft tissue healing period is only a general guide, and restrictions are not lifted automatically on completing 6 weeks. Whether to relax them in the end must be decided by the doctor for the individual case. Korfitsen 2023 also stressed that the current medical evidence does not support applying the same set of strict restrictions to every patient, and that adjusting the approach to the individual case is reasonable.

Dealing with it in Hong Kong homes: low stools, the toilet and the bed

The rules after surgery sound rather tedious, but once the generally small living space in Hong Kong is taken into account, there are quite concrete ways to carry them out. What is really high-risk is often not a single movement angle but a combined movement that the home environment forces on the patient without noticing.

Adjusting the home in the first 6 to 8 weeks after surgery

A toilet that is too low forces the hip to bend past 90 degrees, so a raised toilet seat should be fitted, or a high commode chair with armrests used instead
When picking something up from the floor, a long-handled reacher should be used, to avoid the high-risk combination that comes from bending and twisting the body at the same time
A low bed, common in tenement buildings and small flats, easily makes the joint over-flex and rotate inwards on getting up. The patient should sit on a higher bed edge with the feet apart and not crossed, and when getting out of bed at night should first sit upright and then stand up slowly
When lying on the side, put a pillow between the legs to stop the upper thigh going inwards across the midline of the body, and when lying flat also put a pillow between the legs to keep them apart
Do not try crossing the legs, squatting to use the toilet or lying on the operated side on your own just because 6 weeks have passed. Wait until follow-up confirms that restrictions can be relaxed

This home modification and guidance on everyday movements is where home physiotherapy is most useful. When Nova Health’s registered physiotherapists visit a hip replacement patient for a home environment assessment, they help to raise the toilet seat or stool, teach how to use a long-handled reacher, and demonstrate how to pick things up by bending the knees and not the hips, so that the patient does not make the high-risk combination of flexion, adduction and internal rotation by mistake. The therapist also assesses the patient’s strength, gait and abductor control objectively, as a functional reference for the doctor when later considering relaxing the restrictions, and never suggests that the patient cross the legs or lie on the operated side early. When to relax restrictions is in the end for the surgeon to decide at follow-up. The doctor assesses the surgical approach, stability during the operation and the imaging results, and combines this with the physiotherapist’s assessment of function, and together the two settle the timing.

Key points

Traditionally, movements such as crossing the legs, bending past 90 degrees and sleeping on the operated side are relaxed after about 6 to 12 weeks following surgery, because this is when the soft tissue after a posterolateral approach is at its most fragile in healing.
These three movements each involve one part of the high-risk combination of flexion, adduction and internal rotation. It is the combined movement, with several movements put together, that is the real risk, and a single angle will not necessarily cause an immediate dislocation.
Several clinical trials in recent years agree that, as long as the surgical repair is good, relaxing movement restrictions does not raise the dislocation rate (Tetreault 2020; Crompton 2020; Korfitsen 2023 with 8,835 people).
The Hong Kong College of Orthopaedic Surgeons advises that in the first 8 weeks after surgery, forward flexion should not exceed 60 degrees and afterwards not 90 degrees, and that a pillow should be kept between the legs when lying on the side. The University of Hong Kong guidance says that during the 6 weeks to 3 months of recovery, high-risk movements should not be combined.
When restrictions can be relaxed differs from person to person. It is decided individually by the surgeon according to the surgical approach, stability during the operation and age (Hernandez 2020), and the patient should not try early on his or her own.

Frequently asked questions

After a hip replacement, when exactly can the legs be crossed?

The traditional advice is not to cross the legs for the first 6 weeks after surgery (some clinics extend this to 8 to 12 weeks). The reason is that crossing the legs is the same as adduction and internal rotation of the hip at the same time, which is exactly the high-risk combination of movements most likely to cause dislocation after a posterolateral approach. Once the soft tissues have passed the healing period and the joint is confirmed to be stable at follow-up, most doctors relax the restrictions step by step. The exact time, however, must be decided by the surgeon according to the surgical approach and the stability of the joint during the operation, and the patient should not judge it alone. Several randomised controlled trials show that, as long as the surgical repair is good, relaxing the movement restrictions does not raise the dislocation rate (Tetreault 2020).

Is it really so dangerous to bend over to pick things up or sit on a low stool, past 90 degrees?

Hip flexion past 90 degrees alone will not necessarily cause an immediate dislocation. The real risk is the three movements of flexion, adduction and internal rotation happening together, for example when the body also twists to the opposite side while bending to pick up something from the floor. The Hong Kong College of Orthopaedic Surgeons advises that in the first 8 weeks after surgery, forward flexion should not be more than 60 degrees and afterwards not more than 90 degrees, and that bending forward to lift things, squatting and sitting on low seats should be avoided. In daily life, using a long-handled reacher to pick things up, sitting on a high stool, or bending the knees instead of bending forward at the hip avoids the high-risk combination.

Can the patient sleep on the operated side?

In the early period after surgery, lying flat is generally advised, with a pillow between the legs to keep them apart. When lying on the side, a pillow must also be placed between the legs so that the upper thigh does not cross the midline of the body. A recent non-inferiority trial of the posterolateral approach (Peters 2019, 408 people) found that after relaxing the sleeping position restrictions, the dislocation rate was no different from the traditional strict restrictions (1.46% against 1.48%). When the patient can safely lie on the operated side still depends on the soft tissues healing well and being confirmed by the doctor or physiotherapist.

Why do some people say that so many restrictions are no longer needed?

Several high-quality randomised controlled trials and systematic reviews of the past ten years (van der Weegen 2016, Dietz 2019, Crompton 2020 with 6,900 people, Korfitsen 2023 with 8,835 people) agree: after hip replacement by the posterior approach, relaxing the traditional movement restrictions does not raise the dislocation rate, and patients can return to daily life sooner and are more satisfied. The current clinical trend is therefore individualised and not one size fits all. Patients with a low risk of dislocation and a stable joint at surgery can have restrictions relaxed earlier, while high-risk patients are given a more conservative arrangement.