Patella instability

What is it?

The recurrent subjective or objective feeling of the patella coming out of its place.
It is a combination of factors that causes your child’s knee cap to feel unstable either in certain situations or most of the time.

What causes it? Different types?

Multiple causes have been identified and the best simple way to describe them would be to classify them into trauma (accident) related, developmental (growing with the child), congenital (from birth).

Traumatic events: this usually occurs when the knee-cap is directly impacted during sporting events and it becomes unstable secondary to that. This can occur without predisposing causes for instability or can become clinically apparent in cases of predisposing mechanical factors.

In cases caused by developmental predisposing factors, it would be good to mention just a few potential issues that lead to patella-femoral joint PFJ instability.

The most common one would be genu valgum (knock knees) in which the knee cap, which is part of the extensor mechanism (the complex of muscles/tendons/bones extending the knee joint), is being pulled to the outside and if any other structural predisposing factors exist, the knee cap can become unstable.

Other causes, are lateralisation of the tibial tuberosity and patella tendon, trochlear dysplasia (shallow groove where the patella normally sits) or elevation of the knee cap height. Rotational deformities of the lower limbs such as Torsional malalignment syndrome can cause patella instability in some cases.

These normally don’t cause an issue if they present in isolation, however when combined, they increase the risk of continuous PFJ instability.

Congenital knee conditions can cause PFJ instability however these are associated with other conditions and are sometimes part of a syndromic picture (multiple symptoms and signs in relation to a condition).

Symptoms

These can range from pain during sports, dancing or during the most simple activities such as walking or pushing a shopping trolley, to situations when your child’s knee cap keeps popping out (partially or completely).

In some situations just touching the knee cap or coming close to doing so during clinical examination can cause a significant feeling of discomfort (sensation of apprehension)

Possible complications

Recurrent PFJ instability can translate into potential joint cartilage damage and subsequent loose bodies in the joint or early wear and tear – articular degeneration and chronic pain.

The most common issue related to this condition is the reluctance of the child to engage in any sporting activity or even the ability to fully straighten the knee, as this can cause pain or the uneasy feeling of an imminent knee cap popping.

Irreducible knee caps are a rare occurrence and are usually encountered in first time dislocations, particularly in traumatic events.

How can it be diagnosed?

Clinical examination is paramount and offers the most amount of information about the patella femoral tracking or how the knee cap slides on the front of the knee. Assessing the child through a range of motion and determining the rotational profile can particularly aid in the decision-making process and determining the cause/causes for PFJ instability.

A series of investigations ranging from a simple Xray can be very helpful. In more advanced cases of instability and pain, cross sectional imaging can be employed such as an MRI. Rotational profile CTs can be used to confirm and quantify rotational malalignment issues.

Treatment options?

These range from surgical to non surgical ones.

The gold standard for the initial treatment of PFJ instability is physiotherapy and balancing the driving forces around the anterior part of the knee.

This should take place for at least 6 months, however if recurrent symptoms of instability should prevent the child in maintaining a normal function and baseline level of activity, surgical options should be discussed in which one or more of the issues causing instability are addressed.

Recovery

This is essential for any PFJ realignment or stabilisation procedure and is guided by our physiotherapy colleagues. Muscle mass re-gain and strengthening is key to ensuring the outcome of the surgery is optimal.

Frequently Asked Questions

Q: Can my child still play sports with patella instability?
A: Yes, but they may need to take a break during treatment and recovery. Physical therapy and bracing can help them return safely.

Q: Is surgery always necessary?
A: No, surgery is typically considered if conservative treatments fail or if the child has repeated dislocations.

Q: Will my child outgrow patella instability?
A: Some children improve with growth and strengthening exercises, but others may require ongoing management or surgery.

Q: How can I help my child manage pain and discomfort?
A: Rest, ice, compression, elevation, and over-the-counter pain relievers (as recommended by a doctor) can help manage symptoms.