The medial patellofemoral ligament (MPFL) serves as a primary restraint preventing your kneecap from shifting outward during the first 30 degrees of knee bending. When this ligament tears, typically during a kneecap dislocation, the kneecap loses its main stabilising structure, creating a pattern of recurrent instability that may be difficult to fully resolve through physiotherapy alone. MPFL reconstruction replaces this damaged ligament with a tendon graft, aiming to restore the anatomical restraint that helps keep the patella tracking within its groove.
Chronic kneecap instability can develop when the MPFL fails to heal adequately after an initial dislocation, or when repeated subluxations progressively stretch the ligament beyond its functional capacity. Each instability episode can damage the cartilage on the undersurface of the kneecap and the trochlear groove, potentially accelerating joint degeneration.
How the MPFL Functions in Knee Stability
The MPFL connects the inner border of the kneecap to a specific point on the femur, just below a bony prominence called the adductor tubercle. This ligament typically remains relatively slack when the knee is fully extended, but generally becomes more taut as the knee bends, providing primary restraint between 0 and 30 degrees of flexion, the range where the kneecap is often most vulnerable to lateral displacement.
Beyond 30 degrees of knee flexion, the kneecap typically engages more deeply within the trochlear groove, where the bony architecture of the femur generally acts as the primary stabiliser. This helps explain why many patellar dislocations occur with the knee in a relatively straight position, such as when planting the foot and pivoting, or when absorbing an impact with the leg nearly extended.
Why the MPFL Rarely Heals Adequately
Unlike some ligaments that may heal with sufficient scar tissue to restore baseline function, the MPFL frequently heals in an elongated position after a dislocation. This elongated healing often occurs because the kneecap naturally tends to sit in a laterally displaced position once the ligament ruptures, and scar tissue forms across this increased distance. The resulting ligament may appear intact on imaging, but can lack the appropriate tension required to prevent subsequent instability episodes.
Identifying Candidates for MPFL Reconstruction
MPFL reconstruction is often considered when specific clinical patterns emerge. Two or more documented patellar dislocations generally suggest the evaluation for surgical intervention, as the observed recurrence rate after a second dislocation frequently exceeds that following an initial episode. Research tracking recurrence after first-time patellar dislocation suggests that the recurrence risk climbs substantially once a second dislocation occurs. A single dislocation may warrant the consideration of a reconstruction if imaging reveals complete MPFL rupture combined with pre-disposing anatomical factors such as trochlear dysplasia, patella alta, or an increased tibial tubercle-trochlear groove distance.
Persistent apprehension, the sensation that the kneecap will dislocate during daily activities or sport, can also indicate surgical candidacy, even without additional documented dislocations. This apprehension reflects underlying instability that limits function and may not fully resolve with targeted strengthening exercises alone.
Anatomical Factors Affecting Surgical Planning
Pre-operative imaging assesses several anatomical parameters that influence the surgical approach:
- Trochlear dysplasia describes a shallow or flat groove on the femur where the kneecap should track. Mild dysplasia may be addressed with MPFL reconstruction alone, while severe dysplasia often requires additional procedures to deepen the groove (trochleoplasty).
- Patella alta refers to a high-riding kneecap that engages the trochlear groove later in knee flexion, prolonging the range where the MPFL must provide primary restraint. Tibial tubercle transfer may be combined with MPFL reconstruction to lower the kneecap position.
- Tibial tubercle lateralisation describes an outward position of the patellar tendon attachment, creating a lateral pulling vector on the kneecap. When the tibial tubercle-trochlear groove distance exceeds normal parameters, tibial tubercle osteotomy may accompany MPFL reconstruction.
The MPFL Reconstruction Procedure
MPFL reconstruction typically uses a hamstring tendon graft, either harvested from the patient (autograft) or from a tissue donor (allograft). The gracilis tendon, located on the inner thigh, generally provides sufficient length and diameter for the procedure while minimising donor site morbidity.
The surgical technique involves creating bone tunnels or using anchors at the anatomical attachment sites on both the patella and femur. The specific placement of these fixation points significantly influences the ligament’s behaviour throughout the range of knee motion.
Accurate femoral tunnel positioning is an important technical factor; placement that is too anterior can create excessive graft tension in flexion, whereas posterior placement may lead to persistent laxity.
Arthroscopic Versus Open Techniques
Many surgeons perform MPFL reconstruction through small incisions without arthroscopy, as the ligament lies outside the joint capsule. However, arthroscopy provides valuable information about cartilage damage, loose bodies, and the need for additional procedures. Most reconstruction protocols include diagnostic arthroscopy to assess intra-articular structures before proceeding with ligament reconstruction.
💡 Did You Know?
The femoral attachment of the MPFL sits within a few millimetres of the medial collateral ligament attachment, requiring precise anatomical knowledge to avoid creating an overly constrained or inappropriately tensioned reconstruction.
Recovery and Rehabilitation Timeline
The initial post-operative phase focuses on protecting the graft while maintaining knee motion. Weight-bearing typically progresses from partial to full over the first six weeks, with a hinged brace typically locked in extension during walking to protect the healing graft, while the brace is unlocked for supervised range of motion exercises.
- Weeks 1-6: Protected weight-bearing, range of motion exercises, quadriceps activation, and patellar mobilisation. The brace is usually unlocked for a range of motion exercises but locked in extension for walking.
- Weeks 6-12: Progressive strengthening, stationary cycling, and gradual weaning from the brace. Closed-chain exercises such as leg presses and squats begin with a limited range.
- Months 3-6: Sport-specific training begins, including agility drills, cutting movements, and plyometrics. Return to non-contact sport typically occurs around four to six months.
- Months 6-9: Return to contact sport and high-risk activities depends on strength symmetry, functional testing, and absence of apprehension during sport-specific movements.
Factors Affecting Recovery Speed
Patients undergoing isolated MPFL reconstruction without additional bony procedures typically progress faster than those requiring concomitant tibial tubercle osteotomy or trochleoplasty. Cartilage damage discovered during surgery may also modify rehabilitation protocols, particularly weight-bearing progression.
A current concept review of MPFL rehabilitation outlines how these factors are weighed across different surgical protocols.
Pre-operative quadriceps strength correlates with post-operative outcomes. Patients who maintain strength before surgery through targeted physiotherapy may regain function faster. Age, activity level, and compliance with rehabilitation protocols further influence the recovery trajectory.
Outcomes and Long-Term Results
MPFL reconstruction has demonstrated favourable results in preventing recurrent dislocation, with many patients returning to their desired activity level. Redislocation following reconstruction occurs infrequently when appropriate surgical technique and patient selection are employed.
Return to sport rates are generally favourable, though some patients modify their activity choices following reconstruction. Persistent anterior knee pain affects a subset of patients, sometimes related to graft over-tensioning or pre-existing cartilage damage rather than reconstruction failure.
⚠️ Important Note
Patients with severe trochlear dysplasia who undergo isolated MPFL reconstruction without addressing the underlying bony anatomy may experience higher failure rates. Comprehensive pre-operative assessment identifies those who require combined procedures.
Alternatives to MPFL Reconstruction
Conservative management remains an option for selected patients, particularly those experiencing a first-time dislocation without significant anatomical risk factors. Structured physiotherapy focusing on vastus medialis obliquus strengthening, hip external rotator conditioning, and proprioceptive training can help reduce instability symptoms in some individuals.
Patellar stabilising braces provide external support during activity but do not restore the underlying ligamentous deficiency. These braces may help reduce apprehension and allow participation in lower-risk activities while patients consider their treatment options.
Lateral release, a procedure that loosens the tight outer structures of the kneecap, was historically performed for patellar instability but is less commonly utilised as a standalone treatment today. Lateral release addresses lateral tightness but does not restore medial restraint, and can potentially worsen instability when performed in isolation.
When to Seek Professional Help
- Kneecap dislocations occurring more than once
- Persistent sensation that the kneecap will shift out of place during activity
- Inability to return to the desired sport or activity due to knee instability
- Giving way episodes during daily activities, such as stair descent or pivoting
- Kneecap pain that worsens despite several months of dedicated physiotherapy
- Visible lateral shift of the kneecap when bending or straightening the knee
Commonly Asked Questions
How long does MPFL reconstruction surgery take?
The procedure typically requires 60 to 90 minutes, though this time extends when combined with other procedures such as tibial tubercle osteotomy or cartilage treatment. Most patients undergo MPFL reconstruction as day surgery or with an overnight hospital stay.
Will I need to use crutches after surgery?
Crutches are typically required for four to six weeks, with weight-bearing progressing gradually during this period. The duration depends on whether additional procedures were performed and individual healing patterns.
Can both knees be reconstructed at the same time?
Bilateral MPFL reconstruction is technically possible but rarely performed simultaneously due to the prolonged recovery and rehabilitation demands. Sequential reconstruction, with the second knee addressed after the first has recovered, provides safer rehabilitation progression.
What happens if the reconstruction fails?
Revision MPFL reconstruction can address recurrent instability following primary reconstruction. Failure analysis includes assessment of tunnel positioning, graft integrity, and previously unaddressed anatomical factors. Revision procedures may require different graft sources or additional bony procedures.
Is MPFL reconstruction suitable for older patients?
Age alone does not exclude patients from MPFL reconstruction. Functional demands, cartilage condition, and overall health influence candidacy more than chronological age. Patients with significant patellofemoral arthritis may benefit more from alternative procedures.
Next Steps
Two or more patellar dislocations, or a single dislocation accompanied by structural factors like trochlear dysplasia, patella alta, or increased tibial tubercle-trochlear groove distance, represent common indications for evaluating an MPFL reconstruction. Pre-operative anatomical assessment helps determine whether isolated ligament reconstruction is appropriate or whether combined bony procedures are required. Because subsequent dislocations can cause additional cartilage damage, an early medical evaluation can be helpful to discuss long-term joint health options.
If you are experiencing recurrent kneecap dislocations, persistent apprehension during daily activities, or giving way episodes that have not fully resolved with conservative therapy, scheduling a consultation with an orthopaedic surgeon in Singapore can provide a comprehensive evaluation to see which management option best suits your condition.
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