Acetabular Protrusion

Protrusio acetabuli is understood to mean a bulging of the femoral head and acetabulum in the direction of the small pelvis. It can be congenital or caused by certain diseases.

Acetabular Protrusion

What is acetabular protrusion?

In medicine, protrusio acetabuli is when the hip socket (acetabulum) and femoral head bulge towards the small pelvis (pelvis minor), which doctors call protrusion. This leads to restricted movement of the hips in all directions. If the bulge is only visible on one side of the body, a leg shortening is possible.

Protrusio acetabuli often shows up in the context of various diseases, including Marfan syndrome. This condition is a connective tissue peculiarity that is caused by a gene mutation. The protrusion of the hip socket was first described in 1824 in Breslau. See gradinmath for What is Diabetes Mellitus Type 2.

According to studies, around one third of all Marfan syndrome patients have to reckon with protrusio acetabuli, in which both hip joints are affected. The protrusio acetabuli is also known as the Otto-Chrobak pelvis. The German anatomist Adolph Wilhelm Otto (1786-1845) and the Austrian gynecologist Rudolf Chrobak (1843-1910) served as namesakes.

Doctors distinguish between a primary and a secondary protrusio acetabuli. In the primary form there is said to be dominant inheritance. It shows up primarily in women. A protrusio acetabuli, which is caused by various hip diseases, is referred to as a secondary form. It occurs equally in both sexes.


The causes of protrusio acetabuli include osteomalacia, coxarthrosis, Marfan syndrome, fibrous dysplasia and Paget’s disease (osteodystrophia deformans). In some cases, trauma or THA implantations are also responsible for the protrusion of the acetabular cup.

In principle, protrusio acetabuli is a pre-arthrotic deformity. As a result, the femoral head sinks into the acetabulum. The transition to the pathological form is smooth. People over the age of 30 are particularly affected by protrusio acetabuli. If the protrusion shows up in childhood, there is a risk of a serious course.

Symptoms, Ailments & Signs

In the initial stage, the protrusio acetabuli proceeds without symptoms. This is also the reason why the disease is often diagnosed so late. Even in the advanced stage, not every patient experiences painful symptoms. In some sufferers, the change in shape causes secondary wear and tear, with cartilage abrasion and deformity of the femoral head occurring.

In such cases, we speak of protrusion coxarthrosis. What is meant by this is a bulging arthrosis of the hip. As the protrusio acetabuli progresses, there are increasing restrictions of movement in the hip joint. These are initially movements such as spreading, stretching and turning. Later, the affected persons also suffer from pain when resting, which occurs mainly at night.

In addition, they are no longer able to walk without pain. Even a complete stiffening of the hip is possible. In women there is also a risk of narrowing of the small pelvis, which in turn leads to mechanical disabilities. In the event of a birth, this can have a negative effect on the birth process.

Diagnosis & course of disease

Diagnosing protrusio acetabuli is not always easy. This is especially true when it is free of symptoms, so that it can usually only be discovered by chance. If, on the other hand, typical symptoms occur, they are considered an indication of the bulging.

One of the most important examination methods is the preparation of X-ray images. On the images, the doctor can see the entry of the socket base in the direction of the pelvis. The criteria of the X-ray examination include a change or a loss of the so-called Koehler teardrop figure. Crossing the inner pelvic line over the hip joint line and increasing the center-oriel angle are also considered for investigation. The course of the protrusio acetabuli depends on its extent. In some cases, it may be necessary to replace the damaged hip joint with an implant.


Protrusio acetabuli causes those affected to suffer from hip problems. However, these symptoms do not always have to be associated with pain. In most cases, the disease is therefore only diagnosed late, since the symptoms are not clear or only occur in a very mild form.

Furthermore, however, the patient’s hip is severely worn down by the protrusio acetabuli. As the disease progresses, pain can develop if left untreated. Especially at night, the pain can be very uncomfortable and thus lead to sleep disorders or depression. Restricted movement is also not uncommon due to protrusio acetabuli. The stretching and stretching of the entire body is significantly restricted due to the disease.

The treatment of protrusio acetabuli is not associated with complications. In most cases, the symptoms of the disease can be reduced with physiotherapy measures. The life expectancy of the patient is not affected or reduced. In severe cases, however, those affected are dependent on surgical interventions in order to be able to continue to move.

When should you go to the doctor?

Protrusio acetabuli disease must always be treated by a doctor. It comes with various complications elsewhere and does not heal itself, so treating the condition is essential. The sooner the doctor is consulted for Protrusio acetabuli, the higher the chances of a complete cure.

As a rule, protrusio acetabuli does not show any particular complaints or symptoms, so that the disease is unfortunately diagnosed and treated much too late. Early treatment is therefore usually not possible. The affected person suffers from restricted mobility in the hip joint. Should these restrictions occur, a doctor must be consulted immediately. In some cases, there is also pain, which can also be accompanied by pain at rest. Especially at night, this can lead to pain and thus to sleeping difficulties.

Protrusio acetabuli can be diagnosed by a general practitioner or by an orthopedist. However, the treatment depends heavily on the exact severity and type of disease, so that no general prediction can be made here.

Treatment & Therapy

Acetabular protrusion can be treated conservatively or surgically. Which therapy is ultimately most suitable depends on the stage of the protrusion and the symptoms the patient is suffering from. If there is no pain, you usually wait.

Thus, secondary coxarthrosis does not necessarily occur in every person. In principle, an X-ray examination is recommended every two years in order to check the further course of the protrusio acetabuli. If the patient suffers from pain, this is initially treated with conservative means. This can be the administration of painkillers, physiotherapeutic treatments such as physiotherapy exercises, hydrotherapy or electrotherapy.

Weight reduction and the use of orthopedic aids such as walking aids or buffer heels are also considered important. In addition, the patient should move the hip joint slightly. Despite alleviating the symptoms, conservative therapy cannot prevent the protrusio acetabuli from progressing. If the pain and restricted mobility worsen, an operation is often necessary.

In children, there is still the possibility of closing the growth plates. In adult patients, the insertion of an artificial hip joint often makes sense. The long-term results are considered excellent. Problems may arise from a thinned socket floor, which makes it difficult to anchor the artificial acetabular cup in the joint. In such cases, plastic constructive treatments take place, in which mostly the body’s own bones are used.


Preventive measures against protrusio acetabuli are not known. So the suffering is sometimes already innate.


In the case of protrusio acetabuli, those affected usually have only a few and only limited aftercare measures available. For this reason, the patient should consult a doctor as soon as the first symptoms and signs of the disease appear, so that further complications can be prevented. As a rule, no self-healing can occur, so that the person concerned is dependent on medical examination and treatment.

The sooner a doctor is consulted, the better the further course of the disease. The treatment depends heavily on the extent of the protrusio acetabulis, so that no general course can be given. In most cases, patients are dependent on taking various medications, whereby attention must be paid to the prescribed dosage and regular intake.

If there are any uncertainties or side effects, consult a doctor first. Regular check-ups by a doctor are also very important. If the disease is treated by surgery, the person concerned should take it easy after the procedure and protect the affected region in particular.

You can do that yourself

The symptoms caused by protrusio acetabuli can be alleviated with consistent physiotherapy, which noticeably reduces the pain. In everyday life, it is important to interpret the physical signs and assess the pain. The sooner the disease is diagnosed, the better the chances of recovery. However, the difficult to recognize symptoms mean that the diagnosis is often made very late.

In order to reduce the problems, it is advisable to lower the weight. Orthopedic aids are also available. The use of walking aids or special buffer heels alleviates the limitations in everyday life. Targeted physiotherapy and slight movements of the hip joint reduce the pain level. At the same time, the progressive wear process slows down. However, the progression of hip disease cannot be stopped, only delayed. Patients should talk to their doctor about the possibility of surgery. Depending on the situation, this procedure can significantly improve the quality of life.

Especially in sensitive people, the pain and discomfort often lead to psychological problems. In such cases, psychotherapeutic care should be provided in addition to physiotherapeutic measures. In some cities there are self-help groups for arthrosis patients who feel understood here. The exchange helps to deal with the situation better.