Recurrent Dislocation of Patella

A recurrent patellar dislocation occurs when the kneecap (patella) repeatedly slips out of its normal position, usually toward the outer side of the knee. After one dislocation, the tissues that help keep the kneecap in place may become stretched or torn, making further dislocations more likely.

Recurrent dislocation can cause pain, swelling, a feeling that the knee is giving way, and difficulty with activities such as running, jumping, squatting or changing direction.

What is the kneecap and why does it dislocate?

The kneecap sits in a groove at the front of the thigh bone and moves up and down as the knee bends and straightens. Several structures work together to keep it properly aligned.

A dislocation can occur when the kneecap is forced out of the groove, particularly during a sudden change in direction, twisting injury or a fall. In some people, the shape and alignment of the knee also make the kneecap more likely to slip out.

After a dislocation, the tissues on the inner side of the knee that help hold the kneecap in place can become stretched or torn. This can contribute to repeated episodes of instability.

What are the symptoms of recurrent dislocation of patella?

People with recurrent patellar dislocation may experience:

• The kneecap suddenly slipping out of place

• A feeling that the kneecap is going to dislocate or "give way"

• Pain around the front of the knee

• Swelling after a dislocation

• Difficulty bending or straightening the knee after an episode

• Difficulty with running, jumping, squatting or changing direction

• Fear or lack of confidence during activities because the kneecap may slip again

Some patients may also develop pain or damage to the cartilage behind the kneecap after repeated episodes.

How is recurrent patellar dislocation diagnosed?

Diagnosis begins with a detailed history and examination of the knee. I will assess how the kneecap moves, whether it is unstable, and whether there are signs of abnormal alignment or movement.

X-rays are used to assess the bones and the position of the kneecap. An MRI may be recommended to look at the tissues that help stabilise the kneecap and to identify cartilage damage or a small piece of bone or cartilage that may have been injured during a dislocation.

In some patients, additional imaging may be needed to understand the shape and alignment of the knee and to help plan treatment.

Why does the kneecap keep dislocating?

Recurrent patellar dislocation is often caused by more than one factor. These may include:

• Damage or weakness of the tissues on the inner side of the knee that help hold the kneecap in place

• A shallow groove in which the kneecap normally moves

• A kneecap that sits higher than usual

• Abnormal alignment of the leg

• The attachment of the patellar tendon being positioned too far to the outer side

• Abnormal rotation of the thigh bone or shin bone

• General looseness of the joints in some patients

Identifying these factors is important because treatment should address the reasons why the kneecap is unstable, rather than simply treating the most recent dislocation.

Does every patient with recurrent patellar dislocation need surgery?

No. Treatment depends on the number of dislocations, the patient's age and activity level, the amount of instability, associated cartilage or bone damage, and the factors contributing to the problem.

Physiotherapy may be appropriate in some patients, particularly when instability is mild or surgery is not required. Treatment may focus on improving the strength and control of the muscles around the hip and knee and improving the way the kneecap moves.

However, repeated dislocations can cause further damage to the cartilage of the knee and may significantly affect sports and everyday activities. Surgery may therefore be considered when instability continues despite appropriate non-surgical treatment or when the risk of further dislocation is high.

Current expert consensus supports individualized treatment based on the patient's anatomy, risk factors, activity demands and associated injuries.

What happens if surgery is not done?

Some patients can manage their symptoms with physiotherapy, activity modification and other non-surgical measures.

However, if the kneecap continues to dislocate, each episode may cause further injury to the tissues and cartilage around the knee. Repeated instability can also lead to ongoing pain, fear of movement and difficulty returning to sports.

The decision not to have surgery should therefore be based on the severity of instability, the patient's individual risk factors and the effect of the problem on daily life and activities.

What type of surgery may be recommended?

The type of surgery depends on why the kneecap is unstable and whether there is any associated damage.

MPFL (medial patellofemoral ligament) reconstruction may be recommended when the main problem is damage or weakness of the tissues that help keep the kneecap in place. In some patients, this may be combined with a procedure to correct the position of the bone where the patellar tendon attaches to the shin bone (tibia)- tibial tuberosity transfer.

When the shape of the groove in which the kneecap moves is a major cause of instability, a procedure to reshape the groove (trochleoplasty) may be considered in selected patients.

If there is a damaged piece of bone or cartilage, this may also need to be treated.

The exact combination of procedures is therefore decided after a detailed examination and review of the scans. Recurrent patellar instability is often multifactorial, and surgery should be planned to address the specific factors contributing to instability.

When can I return to sports?

Returning to sports should be gradual and should depend on recovery of knee movement, strength, balance and control rather than simply the amount of time since surgery.

Sports involving running, jumping and sudden changes of direction place greater demands on the kneecap and may require a longer rehabilitation period.

A return to sport should be based on your individual recovery and functional assessment.

When should I see an orthopaedic surgeon?

You should consider an orthopaedic evaluation if:

• Your kneecap has dislocated more than once

• You frequently feel that the kneecap is going to slip out

• Your knee repeatedly gives way

• You have persistent pain or swelling after a dislocation

• You are unable to return to sports or activities because of instability

• You have been told that you have cartilage or bone damage associated with a patellar dislocation

Early assessment can help identify the factors causing recurrent instability and guide appropriate treatment.

If you have recurrent patellar dislocation, an individualised assessment is important because the most appropriate treatment depends on the underlying cause of instability.