Patella Instability and Dislocations

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Dr Kau Chung Yuan (许医生)


MRCS (Ireland)

MMed (Ortho)

FRCSEd (Ortho)


Introduction to Patella Instability and Dislocations

Patella (commonly known as the kneecap) instability and dislocations occur when the patella moves out of its normal position in the trochlear groove, leading to discomfort and impaired knee function. This condition can be acute, resulting from a specific injury, or chronic, due to an underlying weakness in the knee structure.

Patella instability is a significant concern as it can affect an individual’s ability to perform daily activities and participate in sports.

Causes of Patella Dislocations

The causes of patella dislocations are multifaceted and are attributed to several factors such as:

Anatomical Factors
  • Shallow Trochlear Groove: A less defined groove in the femur can lead to inadequate support for the patella, increasing dislocation risk.
  • High-riding Patella (Patella Alta): An abnormally high position of the patella concerning the femur can predispose individuals to dislocations.
  • Ligamentous Laxity: Individuals with more elastic ligaments may have a higher predisposition to knee injuries, including patella dislocations.
Traumatic Incidents
  • Direct Impact: A forceful blow to the knee can dislodge the patella from its groove.
  • Twisting Movements: Sudden twisting actions, especially with the foot planted and the knee flexed, can lead to dislocation.
Physical Imbalances
  • Muscle Weakness: Weakness in the muscles around the knee, particularly the quadriceps, can lead to instability.
  • Malalignment: Issues such as flat feet or knock knees (genu valgum) can create abnormal forces on the patella, pushing it out of alignment.

Immediate Symptoms Following Dislocation

Common symptoms that follow after a knee dislocation include:

  • Pain
    Sudden, severe pain at the time of injury, particularly on the front side of the knee.
  • Visible Deformity
    The kneecap may visibly shift to the outside of the knee.
  • Swelling
    Rapid swelling of the knee joint following the injury.
  • Difficulty Bearing Weight
    Challenges in standing or walking on the affected leg.

Symptoms of Chronic Instability

Chronic instability symptoms emerge gradually and typically involve:

  • Recurrent Pain
    Persistent or recurrent pain around the kneecap, especially during physical activity.
  • Feeling of Instability
    The sensation that the knee may give out or is not securely in place during movement.
  • Grinding or Popping Sensations
    Experiencing a grinding or popping feeling in the knee, particularly when bending or straightening the leg.
  • Stiffness and Swelling
    Chronic stiffness and swelling in the knee may worsen after periods of inactivity or intense use.

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Diagnosis of Patella Instability and Dislocation includes a detailed evaluation to accurately identify the cause and extent of the injury.

Clinical Examination
  • Medical History: A detailed account of any previous knee injuries, episodes of instability, or dislocations.
  • Physical Examination: Assessment of knee alignment, muscle strength, ligament stability, and range of motion. The examiner may also perform specific manoeuvres to evaluate patellar tracking.
Imaging Studies
  • X-rays: Standard imaging to assess the alignment of the patella and detect any bone abnormalities or fractures.
  • MRI (Magnetic Resonance Imaging): Provides detailed images of soft tissues, including the cartilage, ligaments, and tendons around the knee. MRI is particularly useful in assessing the extent of damage following a dislocation and in identifying chronic conditions contributing to instability.
  • CT Scan: Occasionally used to evaluate the alignment of the knee joint and the geometry of the femoral trochlear groove.


Non-Surgical Treatment Options

Non-surgical treatment options aim to manage symptoms and support natural healing processes.

  • Strengthening Exercises: Focus on strengthening the quadriceps, hamstrings, and hip muscles to improve knee stability.
  • Flexibility Exercises: Enhancing flexibility, particularly in the hamstrings and quadriceps, can reduce stress on the knee.
  • Proprioceptive Training: Improves the knee’s sensory feedback system, aiding in better control and stability.
Orthotic Devices
  • Knee Braces: Can provide additional support and prevent lateral movement of the patella.
  • Foot Orthoses: Corrects foot abnormalities that may contribute to patella misalignment and instability.
  • Pain Relievers: Nonsteroidal anti-inflammatory drugs (NSAIDs) can help manage pain and reduce inflammation.
Lifestyle and Activity Modifications
  • Activity Adjustment: Avoid activities that exacerbate symptoms, at least temporarily, while the knee heals.
  • Weight Management: Reducing body weight to decrease stress on the knee.

Surgical Interventions

Surgical interventions focus on addressing the structural causes of instability to improve knee function.

Lateral Release

Involves cutting tight ligaments on the outer side of the knee to allow the patella to realign properly within its groove.

Medial Patellofemoral Ligament (MPFL) Reconstruction

The MPFL is often torn during a dislocation. Reconstruction involves using a graft to replace the damaged ligament and securing the patella in its proper track.

Tibial Tubercle Transfer

This procedure realigns the patella by moving the attachment point of the patellar tendon on the tibia. It is particularly useful for patients with high-riding patella (patella alta) or those with significant alignment issues.


In cases where the trochlear groove is too shallow or deformed, this procedure deepens the groove to provide a more stable path for the patella.


Dr. Kau Chung Yuan

MBBS (S’pore)

MRCS (Ireland)

MMed (Ortho)

FRCSEd (Ortho)

Dr Kau (许医生) is a Fellowship trained Orthopaedic Surgeon with a subspecialty interest in Hip and Knee surgery and has been in practice for more than 15 years.

He is experienced in trauma and fracture management, sports injuries, and joint replacement surgery.

  • Fellow of the Royal College of Surgeons Edinburgh, Orthopaedics (FRCS, Edin) 2014
  • Master of Medicine (Orthopaedics), Singapore (MMed) 2013
  • Member of the Royal College of Surgeons Ireland (MRCS, Ire) 2009
  • Bachelor of Medicine and Surgery (MBBS, Singapore) 2004

Prevention Strategies

Prevention strategies are designed to strengthen the knee and reduce the risk of future dislocations.

  • Strengthening and flexibility exercises
    These exercises aim to provide better support and reduce the risk of dislocation by ensuring the knee is well-supported by strong and flexible muscles.
  • Proper technique and training
    It’s important to emphasize correct form and gradually increase activity levels to avoid sudden stress on the knee.
  • Lifestyle modifications
    Maintaining a healthy weight and using supportive footwear or orthotic devices can also significantly reduce the risk.

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Patient Feedback

Ethan Chan
Dr. Kau is an exemplary doctor who is experienced in his field and is very patient with his patients. He walked me through the details of my knee condition and addressed all my concerns. Thanks to Dr. Kau, I had a better understanding of my ACL and MCL injury and the various treatment options available. His advice and treatment have been very valuable to me.
Ming Lee Chua
Dr Kau was very careful and explained clearly the surgery procedures. After surgery, the care while I was in hospital was closely monitored and he even came during weekends! The hip so far has recovered and healed. His ‘predictions’ of when what can happen are so accurate. Trust him.
Teo Pek Suan Diana
I had a very successful total hip replacement done by Dr Kau 4 years ago. 4 months after the operation I was back walking, cycling and swimming. The beautiful job gave me much confidence Dr Kau is most professional and has such great doctor patient communication.

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    Frequently Asked Questions (FAQs)

    What are the first steps to take after a patella dislocation?

    After a patella dislocation, it’s important to apply the RICE method – Rest, Ice, Compression, and Elevation – to reduce swelling and pain. Seeking medical evaluation as soon as possible can help to assess the extent of the injury and plan an appropriate treatment strategy.

    Can patella dislocations become a recurring problem?

    Yes, once the patella has dislocated, there’s an increased risk of recurrent dislocations. The risk is higher for individuals with certain anatomical factors or those who do not follow through with the recommended rehabilitation program.

    How long does recovery from a patella dislocation take?

    Recovery time varies depending on the severity of the dislocation, the treatment method chosen, and the individual’s commitment to rehabilitation. Non-surgical treatment may require several weeks to months, while surgical recovery can take longer.

    Can I return to sports after a patella dislocation?

    Most individuals can return to sports after a patella dislocation, but it depends on the recovery process, the strength and stability of the knee, and the type of sports. A gradual return is recommended to prevent re-injury.