MPFL Reconstruction (Patellar Instability)

Why this approach — at MOS

MPFL reconstruction is a technically precise procedure where the isometric femoral tunnel placement is the most critical factor in success. A tunnel placed even a few millimeters away from the anatomic attachment point causes the graft to be either too tight in flexion (creating articular cartilage overload) or too loose in extension (failing to prevent instability). We use fluoroscopic confirmation of tunnel position during every case.

We also perform a complete pre-operative patellar instability workup — including TT-TG measurement on CT or MRI, trochlear morphology assessment, and patella alta measurement — on every patient before planning surgery. When TT-TG is elevated, we discuss tibial tubercle osteotomy concurrently or staged. When the anatomy is anatomically favorable, MPFL reconstruction alone is appropriate.

Graft selection is individualized. Gracilis autograft is our preference for most patients — it provides adequate size and strength, avoids donor-site morbidity concerns associated with other grafts, and leaves the quadriceps mechanism intact. For revision cases or when the gracilis has been previously harvested, allograft or alternative autograft options are used.

Who is a candidate?

Indications

• Recurrent patellar dislocation (two or more documented dislocations)
• Chronic patellar subluxation (partial displacement) causing pain, apprehension, and functional limitation despite conservative management
• First-time dislocation in high-risk patients (elevated TT-TG >15–20 mm, trochlear dysplasia, hyperlaxity) where re-dislocation risk is very high
• Acute MPFL avulsion in a competitive athlete requiring early return to sport

Contraindications

• Active knee joint infection
• Significantly elevated TT-TG distance without concurrent tibial tubercle osteotomy — MPFL reconstruction alone will fail if the bony lateralizing force is excessive
• High-grade trochlear dysplasia — may require trochleoplasty in addition to MPFL reconstruction (specialized assessment required)
• Severe patellofemoral arthritis where the goal is joint replacement rather than soft tissue stabilization

Conservative Treatment First

After a first patellar dislocation, conservative management is appropriate for most patients. This includes reduction of the dislocated patella (if not self-reduced), a period of immobilization in extension (brace or splint), followed by physical therapy emphasizing VMO (vastus medialis oblique) quadriceps strengthening and hip abductor strengthening to improve patellar tracking. Many patients go on to have no further dislocations after a first episode with structured rehabilitation.

Surgery is typically deferred to a second dislocation in most patients, or to persistent functional instability (subluxation) that limits activity despite a full rehabilitation trial. Exceptions include first-time dislocators with very high-risk bony anatomy, those who cannot afford recurrent episodes in their sport or profession, and those with an acute large MPFL avulsion with documented significant structural disruption.

The procedure

What Is MPFL Reconstruction (Patellar Instability)?

MPFL reconstruction is a surgical procedure that rebuilds the medial patellofemoral ligament — the primary soft tissue restraint preventing the kneecap from dislocating outward. When this ligament tears after a patellar dislocation and does not heal adequately, the kneecap can dislocate again with everyday activities. Reconstruction uses a tendon graft to recreate the ligament and restore patellar stability.

The patella (kneecap) sits in the trochlear groove at the front of the femur and glides up and down during knee bending and straightening. The medial patellofemoral ligament (MPFL) runs from the medial border of the patella to the medial femoral condyle near the adductor tubercle — essentially a tether on the inner side that prevents the patella from sliding or flipping outward (laterally) when the quadriceps contracts. A first patellar dislocation almost always tears the MPFL, which heals in most patients but leaves the medial restraint weaker than before.

After a first dislocation, roughly 15–40% of patients experience a second dislocation. After a second dislocation, the risk of further episodes increases substantially, and the repeated dislocations cause cumulative cartilage damage to the patella and trochlea. MPFL reconstruction restores the passive medial restraint that prevents this cycle.

Patient selection for MPFL reconstruction must account for bony factors — specifically the relationship between the tibial tubercle and the trochlear groove (TT-TG distance) and the depth of the trochlear groove (trochlear dysplasia). When bony anatomy is significantly abnormal, MPFL reconstruction alone may not be sufficient, and a tibial tubercle osteotomy or trochleoplasty may be needed in addition.

What Happens During MPFL Reconstruction?

The procedure is performed at the ambulatory surgery center under general or regional anesthesia. Diagnostic arthroscopy is performed first to inspect the joint for cartilage damage from prior dislocations — chondral injuries occur during dislocation events and should be addressed at the same surgery.

After arthroscopy, small incisions are made at the medial patella and at the adductor tubercle region of the medial femoral condyle. The graft — most commonly the gracilis tendon from the hamstrings (autograft) — is harvested through a small incision near the pes anserinus. The graft is prepared on a side table.

The patellar attachment is established using suture anchors placed in the medial patella, securing the graft to the upper and lower medial patellar border. A small tunnel is drilled in the medial femoral condyle at the anatomic MPFL femoral attachment — the isometric point near the adductor tubercle, precisely localized using fluoroscopy during the procedure.

The graft is passed from the patella beneath the medial retinaculum to the femoral tunnel. Before final fixation, the knee is taken through range of motion and the graft tension is assessed — critically, fixation is done with the knee at approximately 30° of flexion and the patella manually centered in the groove. Over-tensioning the MPFL causes patellofemoral compression and creates medial joint pain; under-tensioning fails to prevent instability. The graft is fixed in the femoral tunnel with an interference screw.

Incisions are closed, and a brace is applied.

Recovery timeline

Frequently Asked Questions