The patellar retinaculum is an important stabiliser of the patellofemoral joint, mainly its medial and lateral components.

The medial patellofemoral ligament is one of the ligaments on the medial aspect of the knee. It spans between the superomedial aspect of the patella and the space between the adductor tubercle and the medial femoral epicondyle. Its main role is to prevent the patella from dislocating laterally.

The MPFL is the primary stabiliser to lateral displacement of the patella providing approximately 50-60% of restraining force.

Knee ligament diagram

Causes of MPFL injury

Injury to the MPFL is most common during a non-contact twisting action in valgus (knee going inwards) most likely during the first 20-30 degrees of flexion as the quadriceps tighten simultaneously and pull the patella laterally. Beyond 30 degrees, the quadriceps tendon and patellar ligament pull the patella posterior into the groove of the knee joint making lateral dislocation of the patella unlikely.

Such dislocation can also occur during contact sports such as rugby and football or netball especially when players are involved in tackles or landing from jumping.

Local factors such as bony deformities, most likely valgus with shallow trochlea or dysplastic patella or hyperlaxity can lead to dislocations especially at teens years.

Symptoms of MPFL injury

Main symptom is pain over the medial aspect of the knee and swelling of the knee joint. A few days later a bruise may become apparent and the knee might feel stiff.

Treating MPFL injury

The Management for the first time dislocation can be Conservative to start with in non-professional sports players and in vast majority of cases with RICE protocol, splinting for the acute period and a full course of physiotherapy symptoms resolve within 4 to 6 weeks. For elite sport players the management would be decided on assessment of each individual case.

For multiple or recurrent dislocations, a knee splint is recommended and most likely a series of imaging is required including long leg alignment X-ray’s, MRI Scan and potentially rotational profile in order to identify the cause of dislocation.

The surgical management will involve reconstructing the MPFL with or without adjuvant procedures and in selected cases deformity correction surgery.

MPFL Reconstruction Surgery

The procedure will be under general anaesthetic and consists of first stage an arthroscopic exploration and assessment of the intra-articular structures including dealing with any potential cartilage pathology and the second stage consisting mini open procedure which involves harvesting the hamstring tendon graft and reconstruction of the damaged ligament.

Once the new ligament/augment is in place, full range of movement will be tested to assure the right tension of the ligament. Protected weight bearing will be allowed with crutches. Outpatient physiotherapy will be arranged, and full recovery is expected within 3 to 4 months.

Risks & Benefits of MPFL Reconstruction Surgery

  • MPFL surgery should help with symptoms such as patellar instability and anterior knee pain.
  • Dealing with the either torn or elongated MPFL should help further dislocation and prevent development of early osteoarthritis.
  • As with any surgical procedures of the lower limb, this type of surgical procedure caries small risks of complications such as blood clots, infection and potential adverse reactions to the anaesthetic.
  • More specific risks will be discussed during your consultation with Mr Nita

Download MPFL Reconstruction Rehabilitation Protocol (154 kb)