Received Aug 18; Accepted Sep Published by Elsevier B. All rights reserved. This article has been cited by other articles in PMC. Abstract Habitual dislocation of patella is a condition where the patella dislocates whenever the knee is flexed and spontaneously relocates with extension of the knee.

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Received Aug 18; Accepted Sep Published by Elsevier B. All rights reserved. This article has been cited by other articles in PMC. Abstract Habitual dislocation of patella is a condition where the patella dislocates whenever the knee is flexed and spontaneously relocates with extension of the knee. It is also termed as obligatory dislocation as the patella dislocates completely with each flexion and extension cycle of the knee and the patient has no control over the patella dislocating as he or she moves the knee1.

It usually presents after the child starts to walk, and is often well tolerated in children, if it is not painful. However it may present in childhood with dysfunction and instability. Very little literature is available on habitual dislocation of patella as most of the studies have combined cases of recurrent dislocation with habitual dislocation.

Many different surgical techniques have been described in the literature for the treatment of habitual dislocation of patella. No single procedure is fully effective in the surgical treatment of habitual dislocation of patella and a combination of procedures is recommended.

Keywords: Habitual, Dislocation, Patella 1. Introduction Habitual dislocation of patella is a condition where the patella dislocates whenever the knee is flexed and spontaneously relocates with extension of the knee.

It is also termed as obligatory dislocation as the patella dislocates completely with each flexion and extension cycle of the knee and the patient has no control over the patella dislocating as he or she moves the knee. Presentation Lateral dislocation or subluxation of the patella in children can present in three different forms.

It can be recurrent when dislocation is episodic, habitual when it occurs during each flexion movement of the knee and permanent when it persists in all positions of the knee.

Permanent dislocation is usually congenital and refers to an irreducible dislocation present since birth and associated with a lateral position of the entire quadriceps mechanism. The distinction between these groups is important as the surgical treatment for each group is quite different. It is usually asymptomatic and is often detected by the parents as an odd looking knee or is detected on routine examination in many children.

However it may present in childhood with features of dysfunction and inability to run because of instability. Further flexion is then possible only if the patella is allowed to dislocate, when a full range of motion is readily obtainable.

Pathophysiology Various pathological factors have been described in the pathogenesis of habitual dislocation of patella. The most important factor is contracture of soft tissues lateral to patella.

Jeffreys in described an abnormal attachment of the iliotibial tract to the patella, producing habitual dislocation in flexion. He also put forward the idea that quadriceps contracture may sometimes give rise to dislocation of the patella. The irritant quality of the solution varied with its components, pH and osmotic pressure. It was not seen in cases with history of trauma.

The fibrosis was evident as low signal intensity cords on T2 weighted images. Histological examination in these cases revealed inflammatory cell infiltration, fibrosis and muscle fibre degeneration. He reported that quadriceps contracture patients may present in a variety of ways. At birth they may present with a stiff extended knee or congenital recurvatum or congenital dislocation.

In later childhood they present with habitual dislocation of the patella. In adults there may be a painful knee due to habitual dislocation and arthritis. He reported that his patients with habitual dislocation had contractures of all parts of quadriceps except vastus medialis.

The contractures were mainly seen in the vastus lateralis the main contributor in over half the cases and rarely in the iliotibial band or rectus femoris. Stretching of the vastus medialis tendon was associated with the laxity of the medial capsule in these patients.

Abnormal bands and connections in the tendinous insertion of the quadriceps were found, and were thought to be of congenital origin. Other abnormalities including a shallow femoral groove, hypoplastic lateral femoral condyle, and lateral insertion of the patella tendon were also noted. A number of patients had history of intramuscular injections in the thigh in the neonatal period leading to contractures later on.

Late presentation in all these cases was caused by unequal growth of muscle and bone so that the effect on the knee was not apparent for a number of years. Most cases presented between the ages of 5 and 12 years when the femur is growing disproportionately to the quadriceps. Family history of dislocation was positive in a few patients and other abnormalities were noticed in some cases. He also noted that quadriceps fibrosis involving the rectus femoris and vastus intermedius alone would result in an elevated and hypoplastic patella.

When the vastus lateralis and the iliotibial tract are involved there is great tendency for habitual dislocation of the patella to occur on flexion of the knee. He noted that habitual dislocation was not seen in all cases in which vastus lateralis and the iliotibial tract were contracted.

Whether or not habitual dislocation occurred depended on factors extrinsic to the quadriceps such as femoral torsion, dysplasia of the lateral femoral condyle, genu valgum, a laterally placed patellar tendon insertion and ligamentous laxity. In recurrent dislocations, there were no contractures of the soft tissue lateral to the patella, but medial stabilisation was found to be weak. In habitual dislocation, where flexion of the knee was always associated with displacement of the patella, both lateral contractures and medial laxity were present.

Genu valgum, defects of the patella and femoral condyles were also present in a few cases of habitual dislocations. He noted that in recurrent dislocation, the medial stabilization of the patella was poor because of weakness of the vastus medialis, dysplasia, generalized joint laxity, or post traumatic medial capsular laxity. In habitual and permanent dislocations of patella, the supero-lateral muscle contracture was the primary pathology. Whether it was idiopathic or due to injection fibrosis; medial laxity or weakness of the medial stabilizers of the patella was secondary.

He noted that a number of bony deformities can be associated with dislocations of the patella, but may not be the actual cause. Corrective osteotomy for genu valgum associated with lateral dislocation of the patella, often failed to control the dislocation; and many patients with severe genu valgum did not suffer from dislocation of the patella.

Bone factors probably had only a small role in the dynamic stability of the patella. EMG studies of vastus lateralis, vastus medialis and pes anserinus muscles were performed in all cases. Weak activity of vastus medialis and fair activity of the vastus lateralis was seen in patients with habitual dislocations.

All patellae were small, hypoplastic and hypermobile but no patient had patella alta. He recommended cautious physical examination regarding patella tracking since radiological examinations, including skyline view do not always show the pathophysiology of patellar instability.

Treatment A number of reconstructive procedures have been described in the literature for the management of patellar instability. No single procedure has shown to be effective in the management of habitual dislocation of patella and a combination of procedures involving proximal and distal reconstruction are recommended. When patella or femoral condyles show severe degenerative changes, patellectomy is advocated Macnab, Most authors have reported habitual dislocation in association with shortening of the quadriceps muscle, and consider that lengthening of the tendon is an essential part of the procedure to allow the patella to remain reduced after the realignment.

Williams described the surgical procedure for realignment of soft tissues in habitual dislocation of patella. He advocated division of abnormal attachment of the fascia lata to the patella followed by division of dense contracted bands within the tendon of attachment of vastus lateralis. This is followed by complete dissection of vastus lateralis from its attachment to the patella and the lateral side of rectus femoris.

If full flexion of knee is possible at this stage, vastus is repaired and the wound is closed. If full flexion is still not possible, either the vastus intermedius tendon requires division or the tendon of rectus femoris needs elongation.

If patella still dislocates after full flexion is achieved, distal realignment is added. During surgery, he found that there were well defined bands, or muscular contractures within the quadriceps in each case.

This generally comprised a dense, fibrous band running along its lower border. This band had a rolled anterior border that sweeps forward to the patella rather than having its main attachment to the tibia. During surgery the tight lateral bands were released from the patella and the incision was continued proximally, lateral to the rectus femoris tendon, thus fully releasing the vastus lateralis.

Vastus intermedius was inspected and divided if tight. Depending on the pathology; medial plication, advancement of vastus medialis across the anterior surface of the patella, patellar tendon transfer or transfer of sartorius to the patella was added. Extensor lag was always present whenever rectus femoris was lengthened which resolved in due course of time with physiotherapy.

A few complications were seen that included wound haematoma, lateral popliteal nerve palsy and wound dehiscence. A flat patellar undersurface and flat femoral groove were commonly seen at review but did not prevent a successful outcome. Redislocation was seen in a few cases and was due to either rectus lengthening not being performed at initial surgery or failure to realign distally when a lateral patellar tendon insertion was detectable clinically, or reformation of contractures.

They recommended that distal procedures alone are certain to fail, and if the procedure involves distal advancement of the tibial tendon the condition will actually be made worse. In other words it is essential to lengthen the quadriceps above the patella rather than to shorten it below the patella. The corrective surgery for habitual dislocation involved release of any superolateral contracture, until the patella remained in the intercondylar groove in the fully flexed position of the knee.

This was not necessary in patients with recurrent dislocation in whom no such contractures were demonstrated. If it was not possible to fully flex the knee at this stage, rectus femoris with or without vastus intermedius was lengthened to achieve reduction in full flexion of the knee. He said that tibial tuberosity transplant might be useful in adults, but in children it could causes genu recurvatum from premature closure of the anterior part of the epiphysis and distal migration of the tibial tubercle and traction spur.

A few recurrences were seen. At re-exploration in each case, recurrent contracture was apparent in the line of the original vastus lateralis, and there had been incomplete elongation of rectus femoris or vastus lateralis. Lengthening of the rectus femoris tendon was also required in many cases in their series.

They found that vastus medialis was so deficient that muscle advancement was not possible. In contrast to other studies, they found that normal patellar tracking was maintained without lengthening of the quadriceps tendon in all cases. They recommended early surgery and showed gradual improvement in the development of the femoral trochlear groove in response to the re-centering of the patellar mechanism.

They believed that even in the presence of severe ligamentous laxity, development of the trochlear groove could be expected during the remaining growth when the patella is realigned at a young age. The surgery included lateral release, advancement of medial retinaculum, and the anteromedial tibial tubercle transfer. The average age at surgery was They performed arthroscopy in all cases and found that chondromalacia of the patella grade III to grade IV was present in all cases.

Erosion of the corresponding lateral femoral condyle was noted in all cases. The major intra-operative finding was contracture of the lateral patellar retinaculum with fibrotic bands in the superolateral aspect of patella.

Second look arthroscopy performed after 1 year of surgery showed no obvious deterioration of the patellar cartilage.

Most of their patients had satisfactory result with great improvement in function after surgery.


Patellar Instability

A direct impact that knocks the patella out of joint A twisting motion of the knee, or ankle A sudden lateral cut [2] Anatomy of the knee[ edit ] The patella is a triangular sesamoid bone which is embedded in tendon. It rests in the patellofemoral groove, an articular cartilage -lined hollow at the end of the thigh bone femur where the thigh bone meets the shin bone tibia. Several ligaments and tendons hold the patella in place and allow it to move up and down the patellofemoral groove when the leg bends. The top of the patella attaches to the quadriceps muscle via the quadriceps tendon , [2] the middle to the vastus medialis obliquus and vastus lateralis muscles, and the bottom to the head of the tibia tibial tuberosity via the patellar tendon , which is a continuation of the quadriceps femoris tendon.


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