1. Medial PatellO-femoral Ligament (MPFL) reconstruction.
What is the MPFL and what is its role in the knee?
The kneecap (patella) plays an important role in knee function. The kneecap sits in a groove (trochlea) and moves up and down with knee flexion (bending) and extension (straightening). It acts like a pulley connecting the quadriceps muscles above and the patellar tendon below.
The Medial Patello-femoral Ligament (MPFL) is a ligament which helps to prevent the kneecap from dislocating (coming out of joint). When you have a kneecap dislocation, the MPFL ruptures, leaving you prone to having the kneecap dislocate again. After your first kneecap dislocation, there is a 20‐ 40% chance that it will happen again. If you have had multiple kneecap dislocations, this risk is even higher.
Many anatomical factors may contribute towards the kneecap dislocating. These include the laxity of your ligaments, the shape and of you kneecap groove, and the position of your kneecap within its groove.
Fig. 1. MPFL reconstruction. A superficial strip of your quadriceps tendon is taken and moved to the inner part of your knee to recreate the MPFL and fixed to the femur either with an anchor or with a screw through a bone tunnel.
What symptoms do people with kneecap instability get?
Some people may not have any symptoms despite having dislocated their kneecap. Others may have persistent pain at the front of the knee or apprehension (the feeling of your knee cap wanting to ‘pop out’) with certain activities. This can be debilitating for some, preventing them from partaking in sport or work. Repeated kneecap dislocations can damage the cartilage surface of the kneecap which may lead to arthritis in the long term.
What are the treatment options?
In general, after a single kneecap dislocation where the kneecap has been reduced (put back in place) without complication, non‐operative treatment can be trialled. This involves ice and swelling management and a knee brace in the acute phase, followed by a tailored physiotherapy program aimed at strengthening the quadriceps muscles. Taping the kneecap or wearing a kneecap brace, may be useful when attempting to return to work or sport.
If you continue to have symptoms of kneecap instability despite these, or if you have any further dislocations of the kneecap, surgical management may be recommended. This usually involves an MPFL reconstruction, sometimes combined with a tibial tuberosity osteotomy (TTO).
What does MPFL reconstruction surgery involve?
An MPFL reconstruction involves taking a superficial strip of your quadriceps tendon as in Fig.1 and using this to reconstruct the damaged MPFL. It is performed in conjunction with an arthroscopy (keyhole surgery) of the knee to assess and address any other damage to the kneecap. You will have at least 5 small incisions over your knee.
It is performed under a general anaesthetic and usually involves an overnight stay in hospital. After surgery your knee will be in a brace for 6 weeks. You will require crutches for 2 weeks. You will be discharged from hospital with pain‐relief medications and occasionally a blood‐thinner to help prevent blood clots (DVT).
What does rehabilitation/recovery involve?
Rehabilitation should be supervised by a physiotherapist. You should be able to walk unaided by ~2 weeks after surgery. Return to work will depend on the demands of your work (approximately 2 weeks for office‐based, 12 weeks for manual work). Most people can return to full sporting activities by ~6 months after surgery.
What are the major risks and complications from MPFL reconstruction?
General risks of surgery include: anaesthetic risks, infection (~1%), blood clots (~1%).
Specific risks for MPFL reconstruction include: pain, knee stiffness, hardware prominence, numbness, and re‐ dislocation of the kneecap.
The patellar tendon attaches to the tibia (shin bone) at the tibial tuberosity. 
