Patella Instability
Patella (Kneecap) Instability
Patella instability — where the kneecap slips out of place or dislocates — can be addressed with targeted soft-tissue and bony procedures to restore stable, confident movement.
Key points
- Recurrent kneecap dislocation or subluxation
- Rotational profile assessment
- MPFL (medial patellofemoral ligament) reconstruction
- Tibial Tubercle Osteotomy (TTO) for malalignment
- Combined procedures where indicated
- Tailored to your anatomy, activity level and goals
Why Tibial Tuberosity Transfer helps — especially in patella alta
Patella alta — a high-riding kneecap — is one of the most important risk factors for recurrent patellar dislocation. When the patella sits too high, it does not engage properly in the trochlear groove at the front of the femur, leaving it vulnerable to slipping sideways, particularly in early knee flexion.
A tibial tuberosity transfer (TTO) addresses this by moving the attachment point of the patellar tendon on the tibia. In patella alta, the key manoeuvre is distalisation — moving the tibial tuberosity downwards (distally). This effectively lowers the patella into a better position within the trochlear groove, improving both stability and patellar tracking throughout the range of movement.
Distalisation works by lengthening the lever arm of the extensor mechanism and increasing the contact area between the patella and the femur. By normalising patellar height, the kneecap engages the bony walls of the trochlea earlier as the knee bends, which provides far greater resistance to lateral displacement. This is especially valuable in patients who have failed previous soft-tissue surgery or who have severe patella alta on imaging.
The procedure can also be combined with medialisation (moving the tuberosity inward) when there is increased TT-TG distance or rotational malalignment, allowing a truly individualised correction based on each patient's anatomy.
Surgery and rehab for MPFL reconstruction
0 – 6 weeks
- Full weight bearing on crutches
- Physiotherapy
6 weeks – 3 months
- Quadriceps strengthening
MPFL Reconstruction and Tibial Tuberosity Transfer
0 – 2 months
- Crutches
- Physiotherapy
- Brace keeping leg straight when weight bearing
- Bending allowed when not weight bearing
2 months – 4 months
- If TTT united, remove brace and full rehab
Valgus alignment of the leg
Valgus describes a knock-kneed posture where the lower leg angles outward relative to the thigh, so that the knees come together or even touch when the ankles are kept apart. This alters the line of pull of the quadriceps and patellar tendon, increasing the lateralising forces on the kneecap and making dislocation more likely.
Significant valgus malalignment is an important but sometimes overlooked contributor to patellar instability. When the mechanical axis of the leg falls medial to the knee centre, the patella is effectively pulled laterally with every step and squat. In these cases, a distal femoral osteotomy (DFO) may be discussed to correct the coronal plane alignment, realign the extensor mechanism and protect the patellofemoral joint.
Surgery
- Usually one night stay in hospital to help control pain
- Lots of local anaesthetic will be given at the time of surgery
Rehab
- Usually full weight bearing from day one as pain allows
- If combined with a TTO (above) then will be bespoke and individual to each patient
0 – 6 weeks
- On crutches
- Physiotherapy
- Partially or fully weight bearing (with or without a brace)
- Full range of movement of your knee
6 weeks – 12 weeks
- Definitely fully weight bearing
- Repeat X-ray to ensure osteotomy healing
12 weeks – 6 months
- Improve with strength and activities
18 months
- Remove plate