Patellar dislocation surgery aims to restore patellofemoral stability, normalize tracking, and prevent recurrent instability that leads to progressive chondral wear and premature osteoarthritis. While acute first-time dislocations often respond to conservative protocols, operative management is required for recurrent instability, underlying anatomical malalignment, or intra-articular osteochondral fractures.
Classification of Patellar Dislocation
- Acute Primary Dislocation: Often sports-related or traumatic. Approximately 55–70% resolve with non-operative functional rehabilitation.
- Recurrent Dislocation: Subsequent episodes triggered by minimal exertion, indicating failure of the medial soft-tissue restraints.
- Habitual Dislocation: The patella dislocates with every cycle of knee flexion, typically driven by severe trochlear dysplasia or patella alta.
- Fixed (Permanent) Dislocation: The patella remains permanently displaced laterally outside the femoral groove, requiring comprehensive bony and soft-tissue realignment.
Surgical Indications
Operative stabilization becomes necessary under the following clinical conditions:
- Recurrent patellofemoral dislocation or persistent subjective instability.
- Displaced osteochondral loose bodies requiring arthroscopic fixation or debridement.
- Failure of guided conservative rehabilitation following a primary dislocation.
- Severe structural risk factors, such as an elevated tibial tubercle–trochlear groove distance (TT-TG > 20 mm) or high-grade patella alta.
Surgical Procedures and Techniques
Diagnostic arthroscopy is routinely combined with open or minimally invasive corrective techniques:
| Procedure | Primary Indication | Success Rate |
|---|---|---|
| MPFL Reconstruction | Ruptured medial patellofemoral ligament; recurrent instability | 90–95% |
| Tibial Tubercle Osteotomy (TTO) | Lateralized extensor mechanism (TT-TG > 20 mm) or patella alta | 80–90% |
| Trochleoplasty | Severe, high-grade trochlear dysplasia (Dejour type B or D) | 80–90% |
| Knee Arthroscopy | Removal of loose chondral bodies and cartilage resurfacing | N/A (Adjunctive) |
1. MPFL Reconstruction
The gold standard for patellofemoral stabilization. The torn native ligament is reconstructed using a gracilis or semitendinosus autograft (or allograft), secured to the patella and the medial femoral condyle (Schöttle’s point) using bioabsorbable interference screws or suture anchors.
2. Bony Alignment Procedures
- Tibial Tubercle Osteotomy (TTO): Involves mobilizing the tibial tubercle medially (to correct the TT-TG distance) or distally (to correct patella alta), securing it with rigid bicortical screws.
- Trochleoplasty: Reshapes a flattened or convex trochlear floor into a congruent groove to re-engage the patella.
Intraoperative and Postoperative Protocol
- Anesthesia: Performed under spinal or general anesthesia, typically supplemented with an ultrasound-guided adductor canal block to provide targeted postoperative analgesia without quadriceps motor blockade.
- Hospital Stay: Conducted primarily as an outpatient (day-case) procedure or with an overnight observational stay.
- Weight-Bearing: Immediate toe-touch to partial weight-bearing with crutches and a hinged knee brace locked in extension, advancing to full weight-bearing as quadriceps neuromuscular control returns (weeks 2–4).
Rehabilitation Timeline and Milestones
- Weeks 0–3 (Protection Phase): Brace locked in extension during ambulation, early passive range-of-motion exercises (0–90°), and isometric quadriceps sets. Desk work resumes.
- Weeks 4–6 (Loading Phase): Progressive brace weaning, gait retraining without crutches, and resumption of driving once emergency braking force is verified.
- Weeks 8–12 (Strengthening Phase): Closed-chain kinetic exercises, stationary cycling, swimming, and targeted hip abductor and core strengthening.
- Months 4–6 (Return to Sport): Straight-line jogging progressing to multi-directional agility drills. Clearance for competitive pivoting sports requires objective functional stability and ≥85–90% limb symmetry on dynamometric testing.
Frequently Asked Questions About Patellar Dislocation Surgery
What is patellar dislocation surgery and how is it performed?
Patellar dislocation surgery comprises surgical procedures aimed at restoring normal patellofemoral mechanics and preventing recurrent lateral slippage. The cornerstone technique is Medial Patellofemoral Ligament (MPFL) Reconstruction, where an autologous tendon graft (such as gracilis or semitendinosus) is anatomically secured to the medial aspect of the patella and the Schöttle point on the medial femoral condyle using bio-composite interference screws or suture anchors.
When is surgery strictly indicated for a dislocated kneecap?
Surgical intervention is recommended in several specific clinical scenarios:
- Recurrent Instability: Two or more episodes of lateral patellar dislocation.
- Displaced Osteochondral Fractures: Chondral or osteochondral shearing fragments that require surgical fixation or arthroscopic removal.
- High-Grade MPFL Rupture: Substantial soft tissue disruption with significant clinical apprehension on examination.
- Underlying Bony Dysplasia: Severe patella alta, excessive TT-TG distance (>20 mm), or Dejour high-grade trochlear dysplasia causing persistent maltracking.
What are the different surgical procedures used for patellar stabilization?
The operative plan is customized based on individual anatomical risk factors:
- MPFL Reconstruction: Reconstructs the primary soft-tissue checkrein resisting lateral patellar displacement.
- Diagnostic Knee Arthroscopy: Evaluates cartilage surfaces and treats associated meniscal or chondral pathology.
- Tibial Tubercle Osteotomy (TTO): Realigns the insertion point of the patellar tendon medially (Fulkerson procedure) or distally to correct abnormal vector pull and patella alta.
- Trochleoplasty: Deepens a flat or convex femoral sulcus to provide bony stability in high-grade trochlear dysplasia.
What type of anesthesia is used, and how long does the operation take?
The procedure is carried out under regional spinal anesthesia or general anesthesia. It is routinely accompanied by a peripheral nerve block (such as an adductor canal block) to minimize immediate postoperative discomfort. The surgical duration ranges from 45 to 90 minutes depending on whether concurrent bony realignment is executed.
How long is the hospital stay after patellar stabilization surgery?
MPFL reconstruction is primarily performed as an outpatient or short-stay procedure. Patients are usually cleared for discharge on the same day or after one night of inpatient observation once pain is managed and safe ambulation with crutches has been demonstrated.
When can patients bear weight and walk after patellar surgery?
Patients can commence partial to full weight-bearing with crutches on postoperative day 1 or 2, provided the knee is supported in a hinged knee brace locked at 0° extension during ambulation. Crutches are gradually weaned off by weeks 4 to 6 as active quadriceps control (e.g., performing a straight leg raise without lag) is restored.
What is the clinical success rate of MPFL reconstruction surgery?
Isolated or combined MPFL reconstruction achieves a clinical success rate of 90% to 95%. It effectively resolves lateral apprehension, eliminates recurrent dislocations (<3%–5% recurrence rate), and significantly improves functional outcome scores such as Kujala and Lysholm scores.
What are the potential complications of patellar stabilization surgery?
Complications are uncommon (<3%–5%) and may include:
- Joint Stiffness: Restriction of knee flexion due to arthrofibrosis, minimized by early passive motion protocols.
- Graft Over-Tensioning: Excessive medial tension causing increased patellofemoral contact pressure and anterior knee pain.
- Patellar Fracture: Rare risk associated with drilling transverse bone tunnels in the patella.
- Infection and DVT: Prevented through perioperative antibiotics and chemical/mechanical thromboprophylaxis.
What is the timeline for returning to driving, work, and sports?
The standard functional recovery timeline progresses as follows:
- Desk Work: 2 to 3 weeks postoperatively (with leg elevation).
- Driving: 4 to 6 weeks for the right leg (upon regaining rapid emergency braking reflexes).
- Low-Impact Training (Cycling, Swimming): 8 to 12 weeks.
- Competitive Pivoting Sports: 4 to 6 months, following objective functional symmetry testing (>90% limb symmetry).
Why is structured physical therapy essential after patellar dislocation surgery?
Postoperative rehabilitation is vital to protecting the graft during the biological incorporation phase. It progressively restores knee flexion without overloading the repair, isolates and strengthens the vastus medialis obliquus (VMO) and hip external rotators, and retrains neuromuscular joint proprioception for safe return to athletic performance.
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