Patellar dislocation


Patellar dislocation

Patellar dislocation


The patellar dislocation occurs when the patella (kneecap) slips out of its normal position. It usually happens in people with anatomical predisposition for the dislocation, either because the femoral sulcus that acts as a track for its motion is flatter than normal (trochlear dysplasia), or due to other changes in the patellar position or alignment.

Normally the first patellar dislocation episode occurs in adolescence and youth, after a knee twist. The more predisposing factors the patient has for the dislocation, the easier the patella comes out of place. In the most severe cases of trochlear dysplasia, a simple movement is enough for the dislocation to occur.

Generally the first episode is treated by an immobilization in a cast for five weeks. In most cases the patella never dislocates again.

When a second episode occurs (recurrent dislocation), or if after the first one the patient feels that the patella tends to come out of place and that their activity is limited due to the fear of dislocation (patellar instability), surgical treatment is indicated.


At Clinica Adler we adjust the surgical treatment to each patient, according to their instability grade. In the minor grades, which correspond to the most frequent cases, a reconstruction of the ligament that holds the patella to the femur, the so-called medial patellofemoral ligament, is enough. This technique is somewhat similar to the one used in the ACL reconstruction. A structure similar to the initial ligament is fashioned, the so-called graft, and it is positioned in its original direction. The graft is obtained from one of the hamstring tendons, and it is attached to the femur and patella through bone tunnels. This technique is not performed by arthroscopy, as the medial patellofemoral ligament runs outside the joint.

In a more severe instability grade, with frequent and even daily dislocation episodes, other additional surgical techniques must be performed, which are aimed to correct any anatomical defect that predisposes to the dislocation. When a severe trochlear dysplasia is present we perform a trochleoplasty, that is to say, a deepening of the femoral sulcus. When an altered patellar height or patellar alignment exist we perform an anterior tibial tubercle osteotomy, in which the place of the tibia where the patellar tendon attaches is cut and its position is changed, either in height or in direction. These are complex techniques that need a comprehensive knowledge of the correct attaching points, and the use of hardware, such as saws and screws. The surgical wounds may end up being quite large.

The postoperative rehabilitation is essential, with an intensive physiotherapy to regain mobility and strength of the knee.
The result is good; the patella becomes stable and the patient can resume their normal activity.

Patellar dislocation in operated patients

Some patients who have already undergone a patellar stabilization procedure may feel that the instability symptoms persist, or that they have even worsened. The reason for this is typically the use of the wrong technique, either because it was wrongfully indicated or because it was not performed correctly.

At Clinica Adler we make a complete study, including MRI and CT scan, in order to determine the cause of the fail and how it can be corrected. We have the necessary knowledge and technical tools to solve the difficulty of treating an already operated knee, where the existing cuttings and tunnels represent a handicap for a new surgery.