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What is the medial patellofemoral ligament (MPFL)?

The medial patellofemoral ligament (MPFL) is a thin band of tissue that helps keep your kneecap (patella) in the correct position.  As you bend and straighten your knee, the patella normally slides within a groove in the thigh bone (the trochlear groove).

If the kneecap slips out of place (partially or fully), it can cause:

  • Feelings of instability
  • Pain
  • Repeated dislocations
  • Wear and tear under the kneecap over time

The MPFL acts as an anchor to stop the kneecap drifting sideways.

If your knee still feels unstable or keeps dislocating, MPFL reconstruction can help improve stability.
 

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What is MPFL reconstruction?

The operation is usually done under general anaesthetic. During surgery:

  • Small cuts are made around the knee.
  • A camera (arthroscope) is used to check the joint.
  • A small hamstring tendon is taken to create a new MPFL (you won’t notice the tendon loss).
  • The new ligament is fixed to the kneecap and thigh bone using X ray guidance.
  • Sometimes the outer side of the knee is loosened (a lateral release) to help the kneecap stay centred.
  • The knee is cleaned, stitched and bandaged before you wake up.

What are the benefits and outcomes of the surgery?

The aim is to stop the kneecap from dislocating or feeling unstable.  Around 90–95% of patients are happy with the results.

What are the risks of surgery?

All surgery carries small risks. Your surgeon will discuss these fully.

Common risks (still rare):

  • Slow wound healing or oozing (<2%)
  • Infection needing antibiotics (<2%)
  • Stiffness requiring extra physiotherapy (<5%)
  • Blood clots (<1%)
  • Small risks from general anaesthetic

Specific risks for this surgery:

  • Temporary (sometimes permanent) numbness near the scars
  • Swelling and stiffness
  • Ongoing front of knee pain in a small number of people
  • Very small risk of kneecap fracture during drilling
  • Metalwork sometimes needs removing later
  • Less than 1% have repeat instability
  • The surgery cannot reverse existing arthritis

What are the alternatives to an MPFL reconstruction?

  • Physiotherapy 

- Strengthening muscles around the knee

  • Managing symptoms without surgery
  • Other surgical options (used in selected cases): 

- Lateral release: loosens tissues on the outer knee (rarely successful alone)
- Tibial tubercle osteotomy: repositions where the tendon attaches to the shin (bigger operation)
- Trochleoplasty: reshapes the groove in the thigh bone (major surgery, only for severe cases)

MPFL reconstruction is usually preferred because it has fewer complications and quicker recovery.

What happens before surgery? 

You will be asked to attend a pre-assessment clinic. This is to ensure you are medically fit for surgery.  It is important that you keep yourself as fit and healthy as possible prior to your operation. 

What happens after surgery?

After the operation, you will wake up in the recovery room.  You will be moved back to the ward once you are awake.

You will be allowed to fully weight bear (FWB) on the operated leg straight away. You will use crutches for the first few weeks after surgery. 

Physiotherapy will begin immediately to help you regain movement and strength. Your rehab programme may be slightly different depending on your needs, but the main aim is to slowly build up your activity with guidance from your physiotherapist

Typical time frames:

•    2–4 weeks off work
•    Driving at 4–6 weeks, when walking safely without crutches
•    Return to sport at 3–4 months

Will I have to stay in hospital?

Most patients go home the same day.  A small number may stay overnight.

Follow-up care?

As well as regular physiotherapy you will also have follow-up appointments with your surgeon.  Your first follow up appointment with your surgeon’s team is usually six weeks after surgery.

If you are concerned about post-operative complications please contact the ward you were discharged from

Useful Contacts

Heatherwood Hospital:

Frimley Park Hospital:

Wexham Park Hospital:

Contact us

If you have any queries relating to this information, please contact the Orthopaedics service.

About this information

Service:
Orthopaedics

Reference:
N/084

Approval date:
13 March 2026

Review date:
1 March 2029

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Important note 

This page provides general information only. It is developed by clinical staff and is reviewed regularly every 3 years for accuracy. For personal advice about your health, or if you have any concerns, please speak to your doctor.