First thing: don't automatically assume your surgeon will impose this rule because a lot don't! Very few do this in the UK, for instance though within the limits of this forum, I have observed it to be more common in the US. But the dislocation factor associated with this is a RISK, not an inevitability so do not get too anxious, obsessive or scared about it. Also don't be scared if you are told this restriction is for life! For one thing, there are lots of surgeons who don't impose this 90 degree restriction rule at all and of those who do, by far the majority only require them for a few weeks, 6 being the most popular. When a hip is replaced, for some time the muscles will be weak and have very little tone. This can cause the stability of the joint to be somewhat compromised and risk dislocations. In order of risk from day one, precautions includes the following: 1. sleeping with a pillow between your legs - in abduction In hospital they will use a special triangular wedge sometimes called an abduction pillow or a Charnley wedge. This makes you keep your legs wide apart so lessening the risk of dislocation while your muscles are at their weakest. When you get home, you will be asked to substitute this with one or two pillows. 2. The 90 degree restrictions This simply means not bringing your knee close to your body in order to reduce the risk of dislocation. Especially important if the approach used was posterior or lateral THR approaches or incisions. You can bend UP to that point but just not beyond it. This is 90 degrees of flexion at the hip If you're still confused, here's some comparisons to explain further And here is a chart explain some of the do's and don'ts! There is also this tip to pick things up from the floor - it's called the 'golfer's reach'! Make sure you have one hand on something stable like a kitchen counter Put your operated leg back as far as you can so it is in line with the straight of your back Bend your good leg and reach down with your free hand As you can see, the operated leg is in a straight line with the body so not violating the rules. It's a very easy manoeuvre but do be careful the first few days and always hold on to something firm like the kitchen counter or an armchair until you are confident with it. 3. no twisting This is also to avoid the risk of dislocation. When you want to turn round, don't spin on the ball of your foot but take many small steps to minimise risk. When you want to turn over in bed, try to keep your feet apart and avoid crossing one leg over the other 4. no crossing legs This is always a good idea after any surgery, even a nose job! Having an anaesthetic temporarily increases your risk of blood clots. Laying with one foot on the other ankle can restrict blood flow in the both legs so it's best avoided! However, in a hip replacement, this can also put the new hip at risk of dislocation 5 Reaching to a bedside table This involves half turning the body so what kind of approach you had is inmportant posterior approach if the table is the same side as your operated leg, then when you reach, you will roll onto that hip (something you will probably NOT want to do anyway!) and cause it to internally rotate thereby risking dislocation Anterior or lateral approaches here the risk is when the table is on the opposite side to the operated hip and half turning will cause you to externally rotate 6. Sliding scale of dislocation risk The biggest worry THR patients have is that of dislocation. But the risk is simply that - a risk. And that risk, while worst in the first few days, reduces as the weeks of healing go by. Why is a hip at more risk of dislocating after a replacement than before? The surgery requires part of the joint capsule to be excised. The capsule is a fibrous bag which encompasses the joint and keeps all the joint fluid in place. It also contributes to the stability of the joint and, with the many small but strong muscles that surround it, keeps the joint from dislocating. When a new metal joint is put in place, eventually other fibrous material grows around the joint and takes the place of the excised capsule. This is known as 'psuedo' (or false) capsule. After about a couple of months, the muscles will have regained much of their strength and tone and the new 'pseudo' capsule has formed, the joint will be as secure as a normal one and you should be able to do pretty much do anything you want to.