What is the trochleoplasty procedure?

Usually, the patella (knee cap) sits in a groove on the end of the femur (thigh bone). As the knee bends and straightens, the patella glides up and down in the groove, which is known as the trochlear groove. In some people, the patella can be unstable and even dislocate (come out of the groove), usually with twisting movements of the knee. There are multiple reasons why a patella may be unstable but sometimes it is because the groove is curved the wrong way, creating a dome, rather than a groove. In this situation, the patella balances precariously on the domed trochlear groove and is very unstable.

Trochleoplasty is a procedure that reshapes a new groove for the patella to sit in and is a powerful way of stabilising the patella.

Who is suitable for a trochleoplasty?

Trochleoplasty is only performed on people who have a very unstable patella and who have a domed trochlear groove. It is generally not suitable for shallow or flat trochlea grooves (usually, an MPFL reconstruction or patella distalisation would be more appropriate in these situations). 

How is a trochleoplasty performed?

Trochleoplasties are performed under a general anaesthetic (the patient is fully asleep). A 10cm incision is made in the front of the knee and the knee joint is exposed. Chisels are used to lift up a very thin flap of the bone and cartilage in the front of the knee. The bone underneath is then reshaped with chisels and burrs to create a new groove. The flap of bone and cartilage is then laid back down. It is usually flexible enough that it conforms to the shape of the new groove. The flap is then fixed in place with some dissolvable suture tape.

Through the same incision, the tendon of the vastus medialis obliquus (VMO) muscle is detached, shifted forward and downward and then reattached. This improves the action of the VMO, which helps to hold the patella in place and also tightens up the tissue on the inner side of the patella to stabilise it further.

The wound is then stitched up.

How long will I be in hospital?

Normally, patients stay in hospital for two nights after a trochleoplasty. This is because the procedure can be very painful and it is easier to manage the pain while in hospital.

How long is the recovery after a trochleoplasty?

You are able to fully walk on the operated leg straight away but often crutches are required for support. Bending and straightening of the knee is encouraged from the start to minimise stiffness and weakness. Persistent pain and swelling is common up to six months after the operation.

You will need to take 3-4 weeks off work.

Physiotherapy commences immediately after the operation, working on regaining range of movement and muscle strength. There is a rehabilitation program that your surgeon will give you that gradually increases your level of activity under the guidance of your physiotherapist. It takes about nine months before it is safe to return to sport.

What is the expected outcome of a trochleoplasty?

The vast majority (over 90%) of people who undergo trochleoplasty for patella instability are happy with the result. It is a very reliable procedure for stabilising the patella. In terms of pain though, the results can be a bit unpredictable. Often, the knee is more comfortable than it was before the operation but the pain may persist and sometimes a non-painful knee can be made painful.

What risks are there for trochleoplasty?

As with any operation, there is a small risk associated with a general anaesthetic, a risk of infection, numbness or sensitivity around the scar and a risk of deep vein thrombosis.

There is chance that despite this operation the patella is still a bit unstable. If this is the case, further procedures, such as an MPFL reconstruction or patella distalisation may be required at a later stage.

We don't know yet whether the chance of developing arthritis in the knee is higher or lower after a trochleoplasty. Hopefully, by improving the shape of the groove and the way the patella travels in it, the chance of developing arthritis is less.