MPFL Reconstruction Information

In a healthy knee the patella (knee cap) sits in a groove (trochlear groove) on the end of the femur (thigh bone). The medial patellofemoral ligament (MPFL) attaches to the inner side of the patella and the inner side of the end of the femur. It is the primary medial stabilise of the patella. The role of this rope like ligament is to prevent the knee from lateral dislocation (dislocating to the outer side of the knee) and subluxation, which is a partial dislocation of the joint. With any lateral movement of the patella the MPFL can be injured or torn. After a patella has dislocated once, the MPFL is often ruptured or stretched and is less reliable in preventing the patella dislocating in the future.

If a patella continues to dislocate or feels unstable, the MPFL can be repaired with a surgical reconstruction to stabilise the patella and return it to its normal state and position within the knee.

A MPFL Reconstruction is a very reliable procedure for stabilising the patella. However in terms of pain, the results are a bit more unpredictable. 


Signs and Symptoms of Patella Dislocation

  • Patella dislocation to the outer side of the knee, causing an obvious deformity. The patella often relocates on its own once the knee is straightened, reversing the deformity. However, damage to the ligament is still sustained
  • Tenderness, swelling and bruising of the knee
  • Severe pain when attempting to move the knee
  • The feeling the knee is unstable and might give way


Common Causes of Patella Dislocation

  • Direct blow to the knee
  • Twisting or pivoting injury to the lower leg, such as with rapidly changing direction
  • Powerful muscle contraction and increased quadriceps angle. The quadriceps angle is the angle between the line of pull of the quadriceps and the line of the pull of the patella ligament. The wider this angle, the harder the quadriceps muscle will try to dislocate the patella when it contracts
  • Congenital abnormality, such as shallow or malformed joint surfaces
  • Patella Alta, where the patella sits too high in relation to the femoral trochlea



It is common that there is intra-articular damage resulting from patella dislocation. A physical examination can reveal instability of the knee but the best current method of identifying a torn or damaged MPFL is by using both plain radiograph and MRI scans in order to reach the appropriate diagnosis. 


Who is MPFL Reconstruction Suitable For?

A MPFL Reconstruction is recommended for those who have had one or more patella dislocations and have ongoing instability of the knee. It is suitable for those with a normal, shallow or flat trochlear groove. If the groove is severely deformed and is domed, a MPFL reconstruction is usually not an appropriate option and a trochleoplasty (reshaping of the trochlea) may be performed instead.