Does Patella Alta Increase Risk for Future Dislocations After Two Prior Dislocations?
Yes, patella alta significantly increases your risk of future patellar dislocations, with studies showing a 2.38-fold increased risk of recurrence, and this risk compounds with each additional dislocation you've already experienced.
Understanding Your Risk Profile
Having already sustained two patellar dislocations places you in a high-risk category for continued instability. The evidence demonstrates that patella alta (high-riding patella) is one of the most important anatomic risk factors for recurrent dislocations 1. In patients with recurrent dislocations, patella alta is present in 60% of cases compared to only 20.8% in patients without dislocation history 2.
Why Patella Alta Matters After Multiple Dislocations
Patella alta increases the knee flexion angle required before your patella can engage the stabilizing groove of the femur (trochlea) 3. This means:
- Your patella remains unstable through a larger range of motion
- Less bony constraint protects against lateral displacement
- Soft tissue repairs alone (like MPFL reconstruction) may be insufficient without addressing the alta
Your Specific Risk Calculation
With two prior dislocations AND patella alta, your risk profile is substantially elevated. The research shows 4, 1:
- Patella alta alone: 2.38 times increased risk (OR 2.38, p=0.004)
- Two or more risk factors present: 29.6-60.2% recurrence rate
- Three risk factors present: 70.4-78.5% recurrence rate
If you have patella alta measured by Caton-Deschamps Index (CDI) of 1.5 or higher, combined with trochlear dysplasia (sulcus angle ≥170°), your probability of experiencing multiple dislocations reaches 78% 4.
Additional Risk Factors to Assess
Beyond patella alta, evaluate for these compounding factors 1, 2, 5:
- Trochlear dysplasia (shallow or flat femoral groove): 4.15-fold increased risk
- Elevated TT-TG distance (>20mm): 2.87-fold increased risk
- Age <25 years or open growth plates: 2.61-2.72-fold increased risk
- Low lateral trochlear inclination angle: Associated with complete MPFL rupture
- High sulcus angle: Indicates severe trochlear dysplasia
The presence of multiple anatomic factors was identified in 58.3% of patients with recurrent dislocations versus only 1.7% of controls 2.
Treatment Implications
Given your history of two dislocations plus patella alta, surgical intervention should be strongly considered 6. The evidence shows:
- Surgical treatment reduces redislocation rates to 15.8% versus 35.7% with conservative treatment
- MPFL reconstruction alone may be insufficient if patella alta is present
- Distalizing tibial tuberosity osteotomy (TTO) should be considered when patella alta is confirmed, as this directly addresses the anatomic abnormality 3
Surgical Decision Algorithm
Proceed with surgery if:
- CDI ≥1.3 (patella alta confirmed) AND history of ≥2 dislocations
- Presence of osteochondral fragments on imaging
- Persistent subluxation between dislocation events
- Multiple anatomic risk factors present (≥2 factors)
Consider distalizing TTO in addition to MPFL reconstruction when:
- CDI ≥1.3-1.5 (moderate to severe patella alta)
- Young, active patient with high functional demands
- Failed prior soft tissue stabilization
Critical Pitfalls to Avoid
Don't rely on conservative treatment alone with documented patella alta and recurrent instability—the redislocation rate remains unacceptably high 6
Don't perform MPFL reconstruction without addressing patella alta—soft tissue procedures cannot compensate for the biomechanical disadvantage created by alta 3
Don't underestimate the cumulative effect of multiple risk factors—each additional factor exponentially increases recurrence risk 1, 2
Measurement Considerations
Ensure accurate assessment of patella alta using 3:
- Caton-Deschamps Index (CDI): Most reliable, measured on lateral radiograph or MRI
- Insall-Salvati Index (ISI): Alternative measurement
- Threshold for pathologic alta: CDI >1.2-1.3
Both CDI and ISI were significantly elevated in patients with complete MPFL rupture after dislocation 5.
Bottom Line for Your Situation
With two prior dislocations and confirmed patella alta, your risk of future dislocations is high enough to warrant surgical correction of the anatomic abnormality. The combination of MPFL reconstruction with distalizing TTO addresses both the soft tissue injury and the underlying structural problem, providing the best chance of preventing future dislocations and maintaining quality of life for athletic and daily activities.