Patella (Kneecap) Instability and Stabilisation Surgery
Assessment, treatment, and recovery
About Patella (Kneecap) Instability
Patella (kneecap) instability occurs when the kneecap moves out of its normal position within the groove at the front of the knee. This may range from a feeling of slipping or apprehension to recurrent dislocation.
Repeated episodes can cause pain, swelling, cartilage damage, and reduced confidence in the knee, limiting daily activities and sport. Appropriate assessment is important to guide treatment and reduce the risk of long-term joint problems.
Structures involved in patella stability
Patella stability depends on a combination of bone shape, soft tissues, muscle control, and limb alignment. Key structures include:
Medial patellofemoral ligament (MPFL)
The primary soft-tissue restraint that helps prevent the patella from dislocating outward.Trochlea
The groove in the femur that the patella sits within. A shallow or flat groove (trochlear dysplasia) increases the risk of instability.Tibial tuberosity
The bony attachment of the patellar tendon, which influences the direction and tracking of the patella during movement.
In addition to these structures, patella stability is influenced by other anatomical and functional factors, including:
Limb alignment (such as knock-knees or genu valgum)
The Q-angle
Generalised ligament laxity
Muscle strength and tone, particularly around the hip and thigh
Rotational alignment, including external tibial torsion and increased femoral anteversion
Abnormalities in one or more of these factors may contribute to patella instability and are considered when planning treatment.
How does patella instability occur?
Patella instability may result from:
A traumatic twisting injury or fall
A direct blow to the knee
Generalised ligament laxity
Anatomical factors present from adolescence
A first dislocation may occur with minimal force if underlying risk factors are present.
Symptoms
Symptoms may include:
A sensation that the kneecap is slipping or about to dislocate
Recurrent dislocation episodes
Pain at the front of the knee
Swelling following activity
Reduced confidence with running, stairs, or sport
Diagnosis
Diagnosis is based on:
A detailed clinical examination
Assessment of alignment, movement patterns, and patella tracking
Imaging to define anatomy and associated injury
Investigations may include:
X-rays to assess alignment and bony anatomy
MRI to evaluate ligament injury, cartilage damage, and soft tissues
CT scans in selected cases to assess bone position and rotational alignment
Treatment options
Non-operative management
Many patients improve without surgery, particularly after a first dislocation.
Non-operative treatment may include:
Physiotherapy focusing on strength and movement control
Bracing during higher-risk activities
Activity modification
Surgery is generally reserved for recurrent instability or when significant anatomical risk factors are present.
Surgical management (select cases)
Surgical stabilisation may be recommended when:
Instability is recurrent
Symptoms persist despite appropriate rehabilitation
There is significant anatomical abnormality
There is associated cartilage damage
The goal of surgery is to improve patella tracking, restore stability, and protect the joint from further damage.
Procedures may include:
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Reconstruction of the main soft-tissue restraint to prevent outward dislocation.
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Realignment of the patellar tendon attachment when bone position contributes to instability.
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Reserved for severe trochlear dysplasia, where the femoral groove is reshaped to better accommodate the patella.
Not all procedures are required in every patient. The surgical plan is individualised based on anatomy, symptoms, age, and activity goals.
Considerations in younger patients
In patients who have not yet completed growth:
MPFL reconstruction may be considered with techniques designed to minimise risk to growth plates
Tibial tuberosity osteotomy and trochleoplasty are usually delayed until growth is complete
Recovery and rehabilitation
Rehabilitation is essential following both non-operative and surgical treatment.
Recovery typically includes:
Early swelling control and protected movement
Gradual strengthening and movement retraining
Progressive return to daily activities
Later sport-specific rehabilitation
Return-to-sport timelines vary but commonly range from 4–6 months, depending on the procedure performed and rehabilitation progress.
Key points to remember
Patella instability can range from mild symptoms to recurrent dislocation
Anatomical factors often contribute to instability
Many first-time dislocations are managed without surgery
Surgery is considered for recurrence or significant anatomical risk
Rehabilitation plays a central role in recovery
Recurrent instability increases the risk of patellofemoral arthritis
Frequently Asked Questions
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Often no. Physiotherapy is usually recommended first. Surgery is considered for recurrent instability or high-risk anatomy.
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Most patients return between 4–6 months, depending on strength, control, and rehabilitation progress.
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Driving may resume once you:
Are off strong pain medication
Are walking without crutches
Can safely control the pedals and perform an emergency stop
This is commonly around 6 weeks, but varies. Always confirm with your insurer.
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Recurrent instability increases the risk of patellofemoral arthritis over time. It is not yet clear whether stabilisation surgery fully prevents this risk.
