Patellar Instability Surgery
What Is Patellar Instability Surgery?
Patellar instability surgery refers to a group of procedures designed to stabilize a kneecap that repeatedly slips or fully dislocates out of its groove on the femur. The most common and central procedure is medial patellofemoral ligament (MPFL) reconstruction, which rebuilds the primary ligament that normally holds the kneecap centered in place. In patients with additional anatomic risk factors — such as a shallow groove or a misaligned tendon pull — this may be combined with a bony procedure to further correct how the kneecap tracks.
The MPFL runs along the inner side of the knee, connecting the kneecap to the femur, and is the main structure preventing the kneecap from shifting sideways. It tears in the large majority of first-time kneecap dislocations, and once torn, it doesn’t reliably heal back to a length and tension that fully protects against another dislocation — which is why recurrent instability is often treated by reconstructing this ligament altogether rather than simply waiting for it to heal.
When Is Patellar Instability Surgery Needed?
Patellar instability surgery is generally recommended for patients who have:
- Recurrent kneecap dislocations, rather than a single, isolated first-time event
- A first-time dislocation combined with a loose piece of cartilage or bone in the joint found on MRI
- Ongoing episodes of the kneecap feeling like it’s shifting or “about to give out,” even without a full dislocation
- Failed a structured course of nonsurgical treatment, including bracing and physical therapy focused on strengthening the muscles that help stabilize the kneecap
- Significant anatomic risk factors for instability, such as a shallow trochlear groove, a high-riding kneecap (patella alta), or a misaligned pull of the quadriceps tendon
A single first-time dislocation without a loose fragment and without major anatomic risk factors is often treated nonsurgically first, since many patients do well with bracing and therapy alone.
How Is Patellar Instability Surgery Performed?
The specific combination of procedures depends on what’s driving the instability, determined through a careful physical exam and imaging that assesses the shape of the groove, the height of the kneecap, and the alignment of the tendon pulling on it.
- MPFL reconstruction — the foundation of most patellar instability surgery. A tendon graft, often taken from the patient’s own hamstring or from a donor, is used to recreate the torn ligament. The graft is anchored to the kneecap and to the femur at the ligament’s natural attachment points, restoring the tension that normally keeps the kneecap centered as the knee bends and straightens.
- Tibial tubercle transfer — in patients whose tendon pulls the kneecap too far to the outside of the groove, the bony attachment point of the patellar tendon on the shinbone is surgically shifted to a more centered position and secured with screws, realigning the direction of pull on the kneecap.
Is MPFL Reconstruction Enough on Its Own?
For many patients, yes. Because the MPFL is torn in nearly every kneecap dislocation, reconstructing it addresses the most common underlying problem and is often sufficient by itself. However, if imaging reveals a significant additional anatomic risk factor — a substantially shallow groove, a notably high-riding kneecap, or a tendon pulling from a significantly off-center position — addressing the MPFL alone may not fully protect against further dislocations. This is why a thorough preoperative evaluation, rather than a one-size-fits-all approach, plays such an important role in planning patellar instability surgery.
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Recovery After Patellar Instability Surgery
- A knee brace is typically used for several weeks, often allowing progressively more bending as healing advances
- Weight-bearing is usually permitted early with the brace locked straight, advancing as strength and comfort improve
- Physical therapy begins soon after surgery, focusing first on restoring motion, then progressing to strengthening the quadriceps and hip muscles that help support proper kneecap tracking
- Return to daily activities without a brace generally occurs within 6 to 8 weeks
- Return to sports, particularly those involving pivoting and cutting, is typically not considered until around 4 to 6 months, once strength testing confirms the knee is ready
When a bony procedure like a tibial tubercle transfer is performed alongside MPFL reconstruction, recovery follows a somewhat more gradual timeline, since the bone itself needs time to heal in its new position before higher-impact activity is introduced.
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Dr. Palsis specializes in the treatment of knee, shoulder, and sports injuries.