Also called patellar dislocationthe dislocation of the patella corresponds to dislocation of the patellofemoral joint, namely the one that connects the femur and the patella. It usually follows a direct or indirect trauma : shock, torsion by internal rotation or sudden change of direction. It’s a trauma common in adolescents, young adults and athletes. “There is a total or partial loss of the normal anatomical relationships of the joint, which means that the joint areas are no longer nested as they should be” specifies Dr. Miniot.
In the vast majority of casesthe East displacement of the patella is external lateral. “The very rare cases of internal dislocations are consecutive to surgical procedures or very large traumas” indicates the specialist.

The dislocation of the patella is very different from that of the knee: the first concerns the joint between the patella and the femur, while the dislocation of the knee concerns the one located between the femur and the tibia.

When it has not spontaneously returned to its place, the Patella luxation is easily visible because the patella is displaced to the side of the knee and palpable. The patient also has difficulty walking or even standing, and the patellar region is usually swollen and painful.
In cases where the dislocation has spontaneously reduced, i.e. put back in place on its own, there may be the presence of a hemarthrosis, namely blood in the joint, due to rupture of the medial patellofemoral ligament (MPFL). “Internal midline palpation of the patella and MPFL is usually painful, and we feel that the patella is abnormally mobile “adds the specialist.
In rare cases, a small bruise can be observed in the inner part of the patella.

When the patella dislocation recurrence more than twicewe are talking regardingpatellar instability. This pathology mainly affects young and active patients and can have two main causes:
– The Medial patellofemoral ligament injuryl, which allows good maintenance of the patella in the joint,
– A patella abnormality or a hyperlaxité.

Any dislocation of the patella should therefore be investigated for potential causes of patellar instability.

“There is four main risk factors known to patellar instability” explains the specialist:
– The dysplastic femoral trochlea : characterized by a loss of the depth of the trochlea, which causes a loss of bone stability of the patella,
– A anterior tibial tuberosity too lateralized,
– A patella too high,
– The rupture of the MPFL : This ligament helps keep the patella in a centered position when the knee is flexed. Its rupture, during a patellar dislocation, predisposes patients to a recurrence of the dislocation. The medial patellofemoral ligament is the functionally most important component of the medial patellar retinaculum.

There are also other secondary risk factors, including: genu valgum – i.e. an inward deviation of the knees – and insufficiently muscular quadriceps.

“When patellar instability is suspected, the patient can be offered a apprehension testcalled smilies test“explains Dr. Miniot.
The patient is lying on his back, the therapist flexes his knee to 90°, and passively brings the lower limb into extension, while pushing the patella outwards. “If the patient is scared or if he contracts his quadriceps out of apprehension, the test is positive,” concluded the sports doctor.

When a patient comes in with an unreduced patellar dislocation, the first thing to do is to put it back in place.

Reduction of patellar dislocation is not very painful and usually does not require sedation, unless the patient is particularly anxious.
The patient must be lying down and relaxed: his dislocated knee is gently extended, this simple movement may be enough. If not, the therapist will apply gentle pressure to the lateral edge of the patella, and push her back medially to get her back in her place.

The reduction of the dislocation generates a immediate pain reliefand restores the knee to its normal appearance.

The first-line treatment consists of immobilize the knee with a removable splint, in order to heal any associated lesions created by the dislocation of the patella. It also allows time for the MPFL to heal when it has been ruptured.
This orthopedic treatment is relatively short, with a soft splint so that the patient can continue to walk and do their activities to avoid amyotrophy. “The patient keeps the splint between 4 and 6 weeks during which we begin physiotherapy and drainage” indicates the specialist.

A dislocation in an unsportsmanlike subject, which has not caused peripheral lesions, will not necessarily be immobilized.

Surgery is indicated in two cases of patellar dislocation:

• In the event of associated lesions: ligaments, cartilage, osteochondrial lesions or even fractures.
• In the event of recurrence of dislocation, associated with one of the 4 risk factors mentioned above (dysplastic trochlea, anterior tibial tuberosity too lateralized, patella too high, rupture of the MPFL).

The purpose of the operation is to stabilize the patella, thanks to the reconstruction of the medial patello-femoral ligament. It is in fact what keeps the patella centered in front of the femur, and which tears and distends as and when episodes of dislocation occur.
The operation is always followed by a immobilization by splint for a period of 4 to 6 weeksand of several months of rehabilitation.

Rehabilitation is essential following an episode of dislocation, and even more so following surgery. If the patient only needs orthopedic treatment, the physiotherapy sessions can begin as soon as the immobilization by splint begins.

“The goal of rehabilitation is to restore muscle quality, to soften the myotendinous chain, to fight once morest the stiffness of the posterior chain and the internal rotators of the hip. Calf and quadriceps muscle work is essential,” insists the sports doctor.

In postoperative, physiotherapy work is important and can be started from the 5th day following the operation. There is then a transition phase and a muscular rehabilitation phase for athletes.
Rehabilitation usually lasts between 4 and 6 months, twice a week. “Athletes have a daily rehabilitation session” specifies the specialist.

After a dislocation of the patella, the resumption of sport must be done cautiously, following complete rehabilitation.
“It can be done generally between 2 to 3 months following orthopedic treatmentand on average following 4 to 6 months if there was surgery“says Dr. Miniot.