What is a medial and lateral retinaculum partial tear and what is the appropriate management?

Medial and Lateral Retinacular Partial Tears

What This Is

A medial or lateral retinacular partial tear is an incomplete disruption of the fibrous tissue layers that stabilize the patella (kneecap) within the femoral groove, most commonly occurring from traumatic patellar dislocation or chronic patellofemoral instability. 1

The patellar retinaculum consists of two key stabilizing structures:

• Medial patellar retinaculum (MPR): Provides critical resistance against lateral patellar displacement, particularly at lower knee flexion angles 2
• Lateral patellar retinaculum (LPR): Balances medial forces and prevents excessive medial patellar translation 1

Injury Mechanism

• Medial retinacular tears typically occur during acute lateral patellar dislocation, with the tear most commonly involving the inferior aspect of the deep layer at the inferomedial patella (not the medial patellofemoral ligament as often assumed) 3
• Lateral retinacular tears are less common but can result from medial patellar instability or iatrogenic injury from overly aggressive lateral release procedures 4
• Biomechanical studies confirm that medial retinaculum integrity significantly increases the force required to dislocate the patella laterally at all flexion angles 2

---

Management Algorithm

Initial Diagnostic Workup

Start with high-resolution MRI of the knee without contrast to definitively identify the location, extent, and layer involvement of retinacular tears. 1

• MRI readily depicts detailed anatomy of retinacular components and injury patterns 1
• CT may be added preoperatively to identify associated osteochondral fracture fragments at the inferomedial patella, which commonly accompany medial retinacular tears 3
• Standard radiographs (including axial/sunrise views) assess patellar alignment, congruence angle, patellar tilt angle, and lateral shift 5

Conservative Management (First-Line for Partial Tears)

For partial tears without complete patellar instability or recurrent dislocation, initial conservative treatment is appropriate:

• Immobilization in extension for 2-4 weeks to allow healing
• Progressive physical therapy focusing on quadriceps strengthening (particularly vastus medialis obliquus)
• Patellar stabilizing bracing during return to activity
• Activity modification avoiding sudden pivoting or deceleration movements

Surgical Management Indications

Proceed to surgical repair if:

• Recurrent patellar instability occurs despite conservative treatment
• Complete functional instability with positive apprehension testing persists
• Associated osteochondral fracture fragments require fixation 3
• Patellar lateral shift exceeds 1.5 cm on imaging 5

Surgical Technique Selection

For medial retinacular tears with lateral patellar instability:

• Medial retinacular repair/plasty is the primary surgical option, achieving reinforced reattachment of the torn region for improved patellar stabilization 3
• Minimally invasive techniques using suture anchors at the inferomedial patella provide stable fixation without requiring grafts, preserving native anatomy 3
• This approach yields excellent outcomes with average Kujala scores of 89.2 at 2 years and minimal recurrent dislocation rates 3
• Medial retinacular plasty produces similar clinical results to formal medial patellofemoral ligament reconstruction for injuries involving the patellar or midsubstance portions 5

For lateral retinacular tears with medial patellar instability:

• Lateral retinacular reconstruction is required, particularly in patients with systemic joint laxity or iatrogenic injury from prior lateral release 4
• Simultaneous medial patellofemoral ligament revision may be necessary if bidirectional instability exists 4

Critical Surgical Pitfall

Avoid routine lateral retinacular release as an adjunctive procedure unless there is documented excessive lateral tightness causing patellar tilt, as this can create iatrogenic medial patellar instability, particularly in patients with inherent joint laxity 4. The consensus regarding indications for lateral release remains lacking, and complications include permanent medial instability 4.

Postoperative Outcomes

• No recurrent dislocations in properly selected patients undergoing medial retinacular repair 3
• Significant improvement in congruence angle, patellar tilt angle, and lateral shift measurements returning to normal range 5
• Median Kujala scores improve significantly postoperatively regardless of specific surgical technique (plasty vs. reconstruction) 5