- SPECIALIST ORTHOPAEDIC SURGEON | MELBOURNE, VIC | ALBURY, NSW | MORNINGTON, VIC |
- 03 9421 6133
- Melbourne & Mornington VIC |
- Albury, NSW
Patellofemoral instability
A condition where the kneecap (patella) moves out of its normal alignment, often causing pain, dislocation, and difficulty with movement.
Patellofemoral instability occurs when the patella does not sit securely within the groove at the end of the femur (thighbone), known as the trochlear groove. Instead, it may shift, slide, or dislocate, particularly during activities that involve bending, twisting, or sudden changes in direction. This instability can be painful and may limit your ability to walk, kneel, squat, or return to sport.
Instability can be due to a traumatic dislocation, anatomical variations, soft tissue imbalance, or generalised ligament laxity. It most commonly affects adolescents and young adults but can occur at any age, particularly following injury.
In one Australian survey of knee surgeons, the mean reported incidence of primary lateral patellar dislocation in the population was 42 per 100,000 per year.
Common symptoms of patellofemoral instability
Symptoms may vary in severity and frequency but often include:
- A sensation of the kneecap ‘giving way’ or slipping out
- Knee pain, especially at the front of the knee
- Swelling or bruising after a dislocation
- Difficulty with stairs, squatting, or kneeling
- A feeling of instability during sport or pivoting movements
- Audible popping or clicking
- Recurrent dislocations or partial dislocations (subluxations)
What causes patellofemoral instability?
Several factors may contribute to patellar instability:
- Previous patella dislocation: Damage to the stabilising structures around the kneecap can make future dislocations more likely.
- Anatomical differences: A shallow trochlear groove, high-riding patella (patella alta), or abnormal alignment of the leg can increase risk.
- Ligament laxity or muscle imbalance: Weakness or tightness in the muscles that control the kneecap may contribute.
- Generalised hypermobility: Some individuals are naturally more flexible, which can affect joint stability.
- Trauma or injury: A fall, sporting injury, or direct blow to the knee can trigger initial dislocation.
How is patellofemoral instability diagnosed
Diagnosis involves a detailed clinical assessment and imaging to understand the underlying cause and extent of instability. This may include:
- Clinical examination: To assess patellar movement, alignment, joint laxity, and signs of tenderness or apprehension.
- X-rays: To check the position of the kneecap and any bony abnormalities.
- MRI scan: To evaluate soft tissue structures, cartilage damage, and ligament integrity.
- CT scan (in select cases): To assess rotational alignment and anatomical relationships.
Understanding the underlying cause of your hip symptoms is an important part of planning appropriate treatment.
Non-surgical treatment options
In cases of mild or first-time instability without major structural damage, non-surgical care may help. These options may include:
- Physiotherapy: Focused on strengthening the quadriceps (especially the vastus medialis oblique or VMO), improving flexibility, and correcting muscle imbalances.
- Bracing or taping: To support the patella and reduce further instability during movement.
- Activity modification: Avoiding high-risk activities while strengthening the knee.
- Pain management: Anti-inflammatories or ice for symptom relief.Activity modification: Avoiding high-risk activities while strengthening the knee.
Dr Hockings will assess whether non-surgical management is appropriate based on your symptoms, anatomy, and response to treatment.
When might surgery be considered?
Surgery may be recommended if:
- You have recurrent dislocations or subluxations
- Non-operative management fails to relieve symptoms
- There is significant damage to the cartilage or ligament structuresnti-inflammatory medications (as appropriate)
- You have anatomical factors that increase the risk of ongoing instability
Dr Jason Hockings performs a range of procedures to address patellofemoral instability, which may include:
- Medial Patellofemoral Ligament (MPFL) Reconstruction: Rebuilds the main ligament that holds the kneecap in place, often using a tendon graft.
- Tibial Tubercle Osteotomy (TTO): Realigns the patella by repositioning the attachment point of the patellar tendon on the shinbone.
- Lateral Release: Releases tight tissues on the outside of the kneecap to allow improved alignment.
- Trochleoplasty: A specialised procedure used in cases of a shallow or flat trochlear groove to create a deeper channel for the patella.
The most appropriate procedure depends on your individual anatomy and the contributing causes of instability. In some cases, multiple techniques may be combined for optimal stability and long-term function.
Recovery after patellofemoral instability surgery
Recovery will vary depending on the procedure performed, but generally includes:
- A short hospital stay (often same-day or overnight)
- Use of a knee brace and crutches for support in the early stages
- Gradual return to weight-bearing and range-of-motion exercises
- A tailored physiotherapy program to rebuild strength and stability
- Return to sport typically within 4–6 months, depending on healing and rehabilitation progress
Dr Hockings and your physiotherapy team will guide you through each stage of recovery with a personalised plan.
If you’re experiencing ongoing pain, stiffness, or reduced movement that is affecting your daily activities or quality of life, a thorough orthopaedic assessment can help determine the cause and guide the most appropriate treatment options for your situation.