Patellar Dislocation

What Is Patellar Dislocation?

The patella normally sits within a shallow groove at the end of the femur, allowing it to glide smoothly when you bend and straighten your knee.

• Subluxation means the kneecap partly slips but returns on its own.
• Dislocation means the kneecap fully moves out of the groove and may need assistance to relocate.

Both types can cause pain, swelling, and a lingering feeling of weakness or instability.

How Patellar Dislocation Happens

Patellar dislocation often occurs when force pushes the kneecap outward.

Common causes include:

• Twisting the knee while it is bent
• Changing direction during sport
• Direct impact on the knee’s inner side
• Sudden slips, missteps, or uneven ground

Most people describe a loud “pop”, followed by immediate pain, swelling, and difficulty bearing weight. Some may see the kneecap displaced to the outer side of the leg before it shifts back on its own or is relocated in the Emergency Department.

Symptoms

A patellar dislocation or subluxation may cause:

• Sharp pain at the time of injury
• Rapid swelling
• A visible shift of the kneecap (in full dislocation)
• Difficulty bending or straightening the knee
• A sense of instability or “giving way”
• Clicking, catching, or knee apprehension
• Difficulty trusting the knee when pivoting or twisting

Because symptoms can overlap with cartilage or ligament injuries, an assessment helps confirm the diagnosis and rule out other causes of knee pain.

Risk Factors for Patellar Instability

Some people have structural or functional factors that increase the chance of recurrence:

• Shallow or flat trochlear groove
• High-riding kneecap (patella alta)
• Lax or hypermobile joints
• Knock-knee alignment
• Abnormal femoral or tibial rotation
• Weaker quadriceps or hip muscles
• Previous dislocation episode

A knee orthopaedic specialist in Sydney can assess these features during physical examination and imaging review.

Initial Care After a Dislocation

Early management aims to support healing, reduce discomfort, and limit swelling.

This may include:

• Rest
• Ice at short intervals
• Compression if recommended
• Elevation
• Simple pain relief if suitable

A brace or crutches are sometimes used briefly, particularly if swelling or pain makes walking difficult.

Once the initial discomfort settles, gentle movement is usually encouraged to maintain mobility and reduce stiffness. If X-rays show no fractures, weight-bearing as tolerated is generally appropriate for many people.

When Imaging Is Helpful

Your clinician may recommend imaging to understand the extent of the injury:

• X-rays to check alignment and rule out fractures
• MRI to assess cartilage, bone bruising, MPFL injury, or structural factors

Identifying these factors helps determine whether rehabilitation alone is likely to be effective or whether other treatments may be appropriate.

When to See a Knee Specialist

You may benefit from seeing a knee specialist, such as Dr Jonathan Negus, if you have:

• A confirmed patellar dislocation
• Recurrent episodes of instability or “near dislocations”
• Persistent swelling, pain, or stiffness
• Difficulty returning to sport or daily activities
• Concerns about long-term knee function
• Uncertainty about whether surgery is needed

A detailed assessment helps create a personalised treatment plan and clarify your options.

Non-Surgical Management

Many first-time patellar dislocations improve without surgery.

Non-surgical care may include:

• Physiotherapy to improve strength and control
• Exercises for quadriceps, hip muscles, and core
• Stretching for tight structures
• Activity modification
• Taping or bracing when suitable

Rehabilitation often focuses on improving the strength of the vastus medialis obliquus (VMO) and hip stabilisers, as these muscles help guide the patella within the groove and reduce the risk of recurrence.

Some people may also benefit from a structured exercise program or hydrotherapy, depending on symptoms and mobility.

When Surgery May Be Considered

Surgery may be discussed if:

• Instability becomes recurrent
• Symptoms persist despite rehabilitation
• A cartilage fragment is displaced
• Underlying anatomical factors significantly increase recurrence risk

Procedures may include:

• Medial patellofemoral ligament (MPFL) reconstruction
• Tibial tubercle realignment
• Alignment correction procedures
• Combined procedures, depending on your anatomy

A knee orthopaedic surgeon in Sydney will discuss which option, if any, may be appropriate for your situation.

Recovery and Rehabilitation

Rehabilitation plays an important role in restoring confidence and stability in the knee. It may include:

• Swelling control
• Restoring knee movement
• Strengthening quadriceps and hip muscles
• Gradual return to activity
• Sport-specific training if required

Recovery timelines vary and depend on factors such as injury severity, any associated cartilage damage, and whether surgery is required.

Next Steps

If you have experienced a patellar dislocation or ongoing knee instability, an assessment can help clarify the cause and guide your treatment pathway.

Book a consultation with Dr Jonathan Negus, a knee specialist and orthopaedic knee surgeon in Sydney.

This information is intended as a general guide and may not apply to every situation. Assessment and treatment recommendations vary depending on individual circumstances. Please speak with a qualified health professional for advice specific to your condition.