Kneecap (patella) stabilisation - what is it?
Kneecap stabilisation or patellofemoral reconstruction is a combination of surgical procedures dependent on a patients particular symptoms and the underlying cause for the unstable kneecap. Surgery is usually only offered when non-operative measures including physiotherapy have not been successful. In situations where recurrent kneecap dislocations are significantly affecting a patient’s quality of life, surgical stabilisation may be required to reduce pain, prevent further dislocation, and improve the trust a patient has in their knee to allow them to return to activities that they wish to. The type of kneecap stabilisation surgery is dependent on the underlying cause for the kneecap instability and often entails a combination of different surgical approaches.
1) Medial patellofemoral ligament (MPFL) reconstruction:
This involves keyhole and minimally invasive open surgery to reconstruct the ligament that naturally runs from the medial border of the patella to the medial epicondyle of the femur. This ligament acts as a check rein and tightens as the kneecap tries to fall out of the groove laterally. If this ligament is deficient either due to previous trauma or due to a soft tissue disorder, a new graft can be placed in to small tunnels in the kneecap and into a socket within the medial aspect of the thigh bone. This graft is normally a single hamstring tendon harvested from the same leg but is occasionally from cadaveric donors or an artificial ligament can be used.
2) Bony realignment surgery:
If the instability of your kneecap is caused by abnormal bony anatomy, meaning your kneecap is either in a higher than normal position (patella Alta) or too lateral of a position, a bony realignment procedure may be the appropriate treatment. This involves moving the distal attachment of your patella tendon at the tibial tubercle (bony lump on the front of you shin bone) into either a more distal (lower) or medial position. This then changes the forces exerted on your kneecap as you move the joint to prevent it being pulled out to the side and dislocated. The precise change in position of the insertion is calculated from pre-operative imaging, specifically an MRI or CT scan to look at your natural relationship between the insertion of the patella tendon and the groove in which your kneecap runs (TT-TG) distance. This procedure is often offered in combination with a medial patellofemoral ligament reconstruction. The tendon is detached with a small block of bone from its insertion on the tibia, moved in to the appropriate new position and fixed with screws under x-ray guidance.
A significant number of severe cases of patellofemoral instability are caused by abnormalities in the groove that the kneecap runs in. In certain severe cases this groove can be flat or indeed domed. This leads to a very significantly unstable kneecap with often multiple and frequent dislocations. If you imagine trying to roll a ping pong ball down an upturned drain pipe instead of a normal piece of guttering, you could see the difficulty that the kneecap would have staying on a domed trochlear groove. In these severe cases, an operation known as trochleoplasty may be offered. This involves an open approach to the knee, elevation of the articular surface of the trochlear and careful use of osteotomes and burrs to create a new groove in the bone underneath the cartilage. The cartilage is then laid back down into position and fixed with special dissolvable tapes and anchors. As the cartilage bed heals to the new knee bony groove underneath, the patella is able to track more comfortably and securely.
Why would I need a kneecap stabilisation procedure?
Kneecap stabilisation surgery is normally offered when non-operative measures have failed and recurrent patella dislocations are significantly impacting on a patient’s quality of life. This may be due to previous trauma leading to insufficiency of the ligaments stabilising the kneecap or due to an anatomical abnormality that has been present since birth leading to poor kneecap tracking.
What happens after surgery?
The recovery following surgery is normally dependent on the combination of operations you have had. For isolated medial patellofemoral ligament reconstructions or bony realignment procedures, you are often able to leave hospital the same day or the next day dependent on your recovery from the anaesthetic. Following a trochleoplasty which is a larger operation, you will normally require a day or two in hospital having analgesia potentially through an epidural or intravenously and intensive physiotherapy. Some surgery requires the use of a brace post-operatively to restrict the range of movement and support the knee and occasionally crutches are required to allow you to walk comfortably.
Following discharge from hospital we recommend you to take adequate analgesia and use ice regularly on the knee to reduce the pain and swelling and allow you to do exercises to regain range of movement and strength within your leg. Over this period of time if you have had an MPFL reconstruction, your surgeon may recommend a brace to restrict the bend in your knee to allow the graft to incorporate without being put under undue stress. Similarly if you have had a bony realignment procedure to allow the bone to heal, you may be in a brace to restrict your range of movement at approximately 90º. If you have had a trochleoplasty, it is normally recommended that full range of movement is encouraged as the pressure of the kneecap within the groove helps the cartilage bed to sit down and heal more efficiently.
Over this period your physiotherapist will encourage you to work on muscle activation and strengthening as well as improve your active range of movement. At approximately six weeks you will have your second check up with your surgeon to ensure things are progressing as we would like.
One could normally discard the brace and crutches over this period of time and get back to fairly normal activities with walking becoming more comfortable and your gait pattern becoming more normal.
As the strength in your leg return and the proprioceptive coordination of your muscles improves, you will be able to return to running and sports as appropriate.
N.B the timescales above are based on the average recovery following surgery. Your surgeon will discuss exactly what the likely recovery milestones will be for your particular combination of surgeries.
Frequently asked questions:
1) Do I need kneecap stabilisation surgery?
We normally would not recommend kneecap stabilisation surgery after one or two dislocations but in the setting of recurring instability despite physiotherapy, we will often recommend surgery.
2) Which procedure would I need?
Your surgeon will take a full history and examination and appropriate imaging will be performed in order to ascertain the underlying cause of your kneecap instability and this will then inform the decision making progress as to which combination of operations will suit your knee.
3) How long until I can drive?
This is dependent on which leg is operated on, the type of car you drive and the precise surgery you have. As a ballpark figure most patients will require six weeks off driving.
4) When can I get back to sports?
One can normally return to sport following kneecap stabilisation surgery between 12 weeks and six months post-surgery.
5) Will my kneecap ever dislocate again?
The aim of the surgery is to reduce the chance of your kneecap dislocating and successful surgery will normally reduce pain and significantly improve the trust that you have in your knee. There are certain occasions where following a significant injury, it is still possible to dislocate your kneecap but normally this would be a type of injury that would cause a normal persons kneecap to dislocate as well.