Patella (Kneecap) Dislocations

Basics of anatomy

The patella engages, turns and rotates between the femoral condyles when the knee starts to flex from a full extended positition. Natural alignment, rotation of the femur and knee, combined with soft tissue and bony anatomy control determines the stability of the patella throughout the range of motion (ROM). The main static factors determining stability of patella are; patella femoral medial ligament (MPFL), the size of lateral femoral condyles, height of the patella, depth of groove (Trochlea) and lateral femoral ligament patella / lateral retinaculum. The height of the patella is measured on x-rays (lateral view) and the rotation of the tibia relative to femoral groove on CT scan (tibial tuberosity TT- TG Trochlea groove distance).

Soft tissue control varies and depends on collagen and muscle control of each individual patient. There are patients who are more prone to patella dislocations and there are stages in growth where there is an increased risk.

Patella dislocations

The patella slides laterally (outside) of the knee early in flexion from full extension. It usually reduces spontaneously in full extension position and if it does not, it can help to cautiously extending the knee. If there is no serious underlying anatomical malalignment, there is a 30% chance of recurring dislocations after to the first dislocation.

Treatment of patella dislocations

Conservative treatment should consist of the following:

Knee braces and rest for 4 weeks, rehabilitation of proprioception (sense of position).

Core stability muscle exercises.

Quadriceps (VMO) strengthening exercises.

Appropriate exercise program to prevent recurrence and facilitate return to sports.

Surgical treatment

(Limited to for recurring dislocations and high-risk patients).

MPFL reconstruction.

Tibial tuberosity medialization procedures.

MPFL reconstruction

Reconstruction of the MPFL with autograft (double-stranded gracilis or semitendinosustendon) has changed the treatment of recurrent patellar dislocation and excellent results can be achieved. Accurate placement of bony boreholes for attachments and tension of the tendon transplant is essential for a good result.

Tibial tuberosity distalisation or medialisation

If the patella is too high (patella alta) or lateral (insertion on tibial tuberosity) medialisation carried of the tibial tuberosity can be performed.

In chronic patella dislocations a lateral retinaculum release required.

Post ‐ operative rehabilitation:

Partial weight bearing mobilization for 4 weeks.

Optional brace for 4 weeks.

Quadriceps and hamstring training program.

Return to the sport 4-6 months.