Kneecap stabilisation surgery

Under normal circumstances, the kneecap sits in a shallow groove at the front of the knee. The kneecap slides freely up and down this groove when the knees are flexed and extended performing tasks such as stairs and squatting.

Instead of a deep socket to maintain the stability of the joint, the kneecap joint (patellofemoral joint) relies on the thigh muscles (quadricep muscles) and surrounding soft tissue for this role.

Due to the huge forces that this joint experiences with every day and sports-related movements, this stability can sometimes be compromised with a traumatic kneecap dislocation.

In other circumstances, the kneecap may be unstable due to inherent, developmental factors. For example, the groove for the kneecap to sit in may not be deep enough or very flexible soft tissue structures in individuals with hypermobility syndrome. When this happens it is sometimes called a patellar subluxation.

Patellar subluxation results in an instability in the knee, which can pull the kneecap out of the groove and towards the outer side of the knee. This is less severe than a knee dislocation, which occurs when the kneecap completely pops out of the groove and sits on the outside of the knee joint.

Kneecap stabilisation surgery is a treatment option that aims to return the kneecap to its correct position in front of the knee.

The symptoms of an unstable kneecap range from the feeling of a minor looseness in the joint, where the kneecap moves slightly out of the groove, to a complete dislocation.

Look out for the following symptoms if you believe that you may have an unstable patella:

• Weakness or buckling in the knee
• Difficulty in straightening the knee
• Pain in the knee, usually at the front, when doing an activity
• Pain in the knee while sitting
• A sensation that the knee can’t support your weight
• The knee feels stiff
• A noticeable creaking or cracking sound when moving the joint
• The knee may be swollen
• A distinctive clunking sensation, this is called patellar maltracking.

If the kneecap repeatedly dislocated, it can cause the supporting ligaments to become stretched. This, in turn, increases the risk of repeated dislocations.

A kneecap stabilisation operation is usually carried out in hospital under general anaesthetic.

You would normally be admitted the evening before the operation if it is in the morning, or early on the day if your operation is scheduled for the afternoon or the evening. This allows you time to settle in and prepare for the procedure.

During the procedure, your surgeon will make a small incision down the front of your knee. The consultant will then assess the problem and then determine which procedure is best to stabilise the kneecap, such as an arthroscopic patella realignment.

Depending on the underlying cause of the kneecap instability, patellar stabilisation surgery can be performed in a number of ways.

One part of the surgery will often involve tightening up the stabilising soft tissue structures on the inside of the kneecap. This can help to prevent the kneecap from dislocating sideways in the opposite direction (laterally).

Another part of the surgery can be simultaneously releasing some of the structures towards the outside (lateral) aspect of the kneecap. This will be considered if these structures are considered too tight and the release can prevent excessive pulling of the kneecap laterally, which can lead to dislocation.

In many cases surgeons will also move the insertion point of the patellar tendon further towards the inside of the knee. This part of the procedure is termed a tibial tuberosity transfer. This positions the patellar further towards the inside of the patellofemoral joint groove leading to less chance of dislocation.

Depending on the exact type of kneecap surgery undertaken, it is normal for patients to be placed in a knee brace for the initial four to six weeks after surgery to allow only limited amount of movement in the knee.

Patients may also be non-weight bearing or partial weight bearing for a period of time. This is to allow the bone to heal if a tibial tuberosity transfer has been performed and to allow the soft tissue tightening to heal.

Once these restrictions have been lifted, physiotherapists will create a comprehensive rehabilitation package to help you return to activities of daily living and sports as appropriate. These exercises will help you to strengthen the muscles in the leg, which will help the healing of the knee following surgery.

The benefits of a kneecap stabilisation procedure are to manage knee pain and return a full range of motion to the leg.

If the kneecap has been repeatedly dislocated, a kneecap stabilisation can help reduce the chance that the kneecap will dislocate in the future. This will reduce any further damage to the knee, which may delay the need for further, more significant, surgery, such as a kneecap replacement or knee replacement surgery.

Most people who have knee stabilisation surgery make a full recovery and don’t experience complications. However, there are some potential side effects. Your consultant surgeon will discuss the potential risks with you prior to surgery.

Complications can include:

• Pain
• Bleeding
• Damage to nerves
•  Damage to blood vessels
•   Infection of the surgical wound
• Infection in the knee