Patellar Dislocation

**Patellar dislocation** occurs when the kneecap (patella) is displaced from its normal position. The patella normally sits in the **trochlear groove** of the femur (thighbone) and is held in place by various soft tissue structures. **Anatomy of Patellar Stability:** **Bony Stability:** - **Trochlear groove**: The "track" the patella sits in - **Patellar shape**: Triangular shape fits the groove - **Tibial tubercle position**: Where the patellar tendon attaches **Soft Tissue Stability:** - **Medial Patellofemoral Ligament (MPFL)**: Primary restraint to lateral dislocation - **Medial retinaculum**: Additional medial support - **Vastus medialis obliquus (VMO)**: Dynamic medial restraint - **Lateral retinaculum**: Lateral support - **Quadriceps tendon**: Above - **Patellar tendon**: Below **The MPFL — Key Structure:** The medial patellofemoral ligament is the primary soft tissue restraint preventing lateral patellar dislocation: - **95% torn** with first-time dislocation - **Heals with scar tissue** but often functionally inadequate - **Reconstruction** is common surgical procedure - **Critical for long-term stability** **Why Lateral Dislocation?** The patella almost always dislocates laterally due to: - **Q angle**: The angle at which the quadriceps muscles pull the patella laterally - **Higher Q angle in females**: Wider pelvis = more lateral pull - **Trochlear groove anatomy**: Steeper lateral side - **Direction of injury forces**: Usually push patella laterally - **Anatomic predispositions** common in those affected **Types of Patellar Dislocations:** **1. First-Time (Acute) Dislocation:** - Initial event - Patient may not have prior issues - Often requires reduction (if not spontaneous) - High risk of recurrence **2. Recurrent Dislocation:** - Repeated episodes - Often with progressively less trauma - May become "habitual" - Different treatment approach **3. Voluntary Dislocation:** - Patient can subluxate at will - Often psychological component - Surgical treatment generally avoided **4. Habitual Dislocation:** - Occurs every time knee bends - Severe instability - Childhood onset typical - Different anatomy **Mechanism of Injury:** **Direct Mechanism:** - Direct blow to patella - Forces it laterally out of groove - Less common than indirect **Indirect Mechanism (Most Common):** - Twisting injury with foot planted - Knee flexion with valgus stress - Sudden direction change - Combined hip-knee mechanics - Examples: Cutting in basketball, dance jumps, soccer pivots **Predisposing Factors:** **Anatomic:** - **Trochlear dysplasia**: Shallow trochlear groove - **Patella alta**: High-riding patella - **Increased TT-TG distance**: Tibial tuberosity-trochlear groove - **Genu valgum**: Knock knees - **Increased Q angle**: Wider pelvis effect - **Ligamentous laxity**: General hypermobility **Activity-Related:** - Cutting and pivoting sports - Dance and gymnastics - Jumping sports - Sudden direction changes - High-velocity activities **Demographics:** - **Adolescent females** highest risk - **Athletes** in specific sports - **Family history** common - **Hypermobility syndromes** **Associated Injuries:** Patellar dislocations frequently come with other injuries: **1. MPFL Tear (95%):** - Almost universal in first-time dislocations - Often complete tear - May heal with scar but functionally compromised - Reconstruction is common procedure **2. Osteochondral Fractures (40%):** - Small bone-cartilage fragments - Often from patella undersurface - May need surgical removal - Can affect long-term outcomes **3. Cartilage Damage:** - Wear on patella undersurface - May develop arthritis - Common long-term consequence - Critical to assess and treat **4. Other Knee Injuries:** - Sometimes coexists with ACL/meniscus injuries - Particularly in high-energy injuries - Comprehensive evaluation needed **Spontaneous Reduction:** Many patellar dislocations reduce spontaneously when the patient straightens the leg: - **Common occurrence** - **Patient may not realize** the patella was out - **Pain and swelling** still develop - **Diagnosis often missed** if no clear deformity - **Imaging important** even with spontaneous reduction

## Root Causes **Patellar dislocations result from a combination of injury forces and underlying anatomic factors:** **Primary Mechanisms:** **Indirect Mechanism (Most Common - 70-80%):** *Twisting Injury:* - Foot planted on ground - Body rotates over planted foot - Knee experiences valgus + rotation forces - Patella forced laterally out of groove - Common in: basketball cutting, soccer pivoting, dance jumps *Sudden Direction Change:* - Quick lateral movement - Combined hip and knee mechanics - Acceleration force changes - Common in cutting sports **Direct Mechanism (20-30%):** *Direct Blow:* - Force directly on patella - Pushes patella laterally - Less common than indirect - May cause more cartilage damage *Falls:* - Direct impact to knee - Forces may be complex - May combine direct and indirect - Various injury patterns **Risk Factors:** *Anatomic Factors (Most Important):* **1. Trochlear Dysplasia (Shallow Groove):** - The groove the patella sits in is too shallow - Most important predisposing factor - Genetic component - Present in many recurrent dislocators - Severity grades the risk **2. Patella Alta (High-Riding Patella):** - Patella sits higher than normal in trochlear groove - Less contact with stabilizing groove - Increased risk of slipping out - Measured by Insall-Salvati ratio on imaging **3. Increased TT-TG Distance:** - Tibial Tuberosity to Trochlear Groove distance - Greater than 20 mm increases risk - Measured on imaging (CT or MRI) - Surgical consideration if very high **4. Genu Valgum (Knock Knees):** - Knees angle inward - Alters mechanics - Increased Q angle - Lateral pull on patella **5. Increased Q Angle:** - Wider pelvis (females more) - Lateral quadriceps vector - Patella pulled laterally - More common in females **6. Generalized Hypermobility:** - Ligamentous laxity throughout body - Specific syndromes (Ehlers-Danlos) - Increased general dislocation risk - Often family history **Activity-Related Risk Factors:** *High-Risk Sports:* - **Basketball**: Cutting and pivoting - **Soccer**: Direction changes - **Dance**: Jumps and rotations - **Gymnastics**: Landing and twisting - **Cheerleading**: Stunts and tumbling - **Football**: Tackling and contact - **Rugby**: Similar mechanism - **Skiing**: Twisting falls - **Lacrosse**: Cutting and contact *Lower-Risk Sports:* - **Swimming**: No impact - **Cycling**: Limited rotation - **Rowing**: Repetitive but stable - **Distance running**: Less rotation **Demographic Risk Factors:** *Female Sex (2-3x More Affected):* Multiple factors contribute: - **Wider pelvis** = higher Q angle - **Different hip-knee alignment** - **More common in females overall** - **Hormonal factors** in some studies - **Higher participation** in dance, gymnastics *Age:* - **Peak ages 15-19** - **Skeletal immaturity** in younger - **Growth-related changes** - **Activity demands** match age *Family History:* - **Strong genetic component** - **Shared anatomic factors** - **Often multiple family members affected** - **Predisposing conditions** *Connective Tissue Disorders:* - **Ehlers-Danlos syndrome** - **Marfan syndrome** - **Generalized hypermobility** - **Down syndrome** (higher risk) **Why First-Time Vs Recurrent Matters:** *First-Time Dislocator:* - May have specific injury mechanism - May have anatomic factors not previously recognized - 50% recurrence rate without treatment - Important to assess for predisposing factors *Recurrent Dislocator:* - Usually has significant anatomic factors - May develop over time - Less force needed each time - May become voluntary - Often needs surgical treatment **The Anatomic-Functional Connection:** Most patellar dislocations result from: 1. **Predisposing anatomy** (often unrecognized) 2. **Triggering injury** (specific event) 3. **Failed soft tissue restraints** (MPFL tear) 4. **Compensatory mechanisms** (over time) 5. **Cumulative damage** (cartilage, etc.) Understanding these factors guides treatment decisions. **Position-Specific Risk in Sports:** *Basketball:* - Point guards (cutting) - All positions during defensive moves - Landing from jumps *Soccer:* - Defenders (cutting back) - Midfielders (constant direction change) - Forwards (cutting near goal) *Dance:* - Ballet dancers (pirouettes) - Modern dancers (jumps) - All forms with rotation *Gymnastics:* - Floor exercise (landings) - Balance beam (movements) - Tumbling (rotations)

## Treatment Approach **Treatment depends on:** - First-time vs recurrent dislocation - Severity of associated injuries - Patient age and activity level - Anatomic predisposing factors - Specific findings on imaging ## First-Time Dislocation Treatment **Reduction (If Needed):** *Manual Reduction:* - Often spontaneous when leg extended - If not reduced: gentle extension of knee with pressure to redirect patella - Usually painless procedure - Confirms diagnosis *Important*: - Document neurovascular status - Note time of injury - Brief immobilization initially - Pain management **Initial Conservative Treatment:** *Phase 1 (Weeks 0-2): Acute Management* - **Brace or knee immobilizer**: Stabilize patella - **Crutches**: Weight-bearing as tolerated - **Ice**: Reduce swelling - **NSAIDs**: Pain management - **Compression**: Reduce edema - **Elevation**: Help with swelling *Phase 2 (Weeks 2-6): Initial Rehabilitation* - **Brace** continues - **Gentle range of motion** - **Quadriceps activation**: Especially VMO - **Hip strengthening**: Important for kinetic chain - **Walking without crutches** - **Pool therapy** if available *Phase 3 (Weeks 6-12): Progressive Strengthening* - **Brace weaning** - **Progressive resistance**: Squats, lunges - **Single-leg activities** - **Plyometric introduction** - **Sport-specific drills** *Phase 4 (Weeks 12+): Return to Sport* - **Patellar stabilization brace** initially - **Full sport participation** - **Continued strengthening** - **Long-term monitoring** **Surgery for First-Time Dislocation (Selected Cases):** *Indications:* - **Osteochondral fracture** with loose body - **Significant cartilage damage** - **Anatomic abnormalities** (severe) - **Elite athletes** wanting fastest return - **Compromised reduction** *Procedures:* - **Loose body removal**: Arthroscopic - **MPFL repair vs reconstruction**: Debate - **Bony procedures**: Less common acutely ## Recurrent Dislocation Treatment **Surgery Often Needed:** *Indications:* - **2 or more dislocations** - **Continued instability symptoms** - **Career-impacting** - **Activity-limiting** - **Specific anatomic factors** *Surgical Approaches:* **1. MPFL Reconstruction (Most Common):** *Procedure:* - Tendon graft (usually hamstring) - Attached to patella and femur - Restores medial restraint - Anatomic reconstruction *Outcomes:* - 85-95% return to sport - 5-15% recurrence rate - Excellent patient satisfaction - Modern preferred procedure **2. Tibial Tubercle Transfer:** *Procedure:* - Move attachment point of patellar tendon - Address bony alignment - Combined with soft tissue work often - More extensive surgery *Indications:* - High TT-TG distance - Patella alta - Significant bony abnormalities - Combined procedures **3. Trochleoplasty:** *Procedure:* - Reshape trochlear groove - Make groove deeper - Complex procedure - Selected cases *Indications:* - Severe trochlear dysplasia - Failed prior surgery - Specialized centers **4. Lateral Release:** *Procedure:* - Release lateral retinaculum - Often combined with other procedures - Historical procedure, less used alone - Specific indications ## Post-Surgical Recovery **Phase 1 (Weeks 0-2):** - Brace and crutches - Gentle range of motion - Edema control - Initial healing - Surgical wound care **Phase 2 (Weeks 2-6):** - Progressive weight bearing - Range of motion progression - Quadriceps activation - Hip strengthening - Brace continues **Phase 3 (Weeks 6-12):** - Brace weaning - Strengthening progression - Functional exercises - Pool therapy - Bike progression **Phase 4 (Weeks 12-20):** - Sport-specific training - Plyometrics - Cutting and pivoting drills - Return-to-sport criteria **Phase 5 (Weeks 20+):** - Full sport participation - Continued maintenance - Brace possibly initially - Long-term monitoring **Return-to-Sport Criteria (Must Meet ALL):** 1. **Pain-free** at full intensity 2. **Strength symmetry** (≥90% of uninjured side) 3. **Range of motion** equivalent 4. **No apprehension** with sport movements 5. **Functional testing** passed 6. **Sport-specific drills** at full speed 7. **Confidence and psychological readiness** ## Rehabilitation Specifics **The Key Exercises:** *For Quadriceps Activation:* - Straight leg raises - Quad sets - Wall slides - Mini squats progressing - Single-leg squats (when ready) *For VMO Strengthening:* - Inner range terminal knee extension - Multi-angle quad sets - Specific positioning - Biofeedback if available *For Hip Strengthening (Critical):* - Clamshells - Side-lying leg raises - Bridges (double and single) - Monster walks with band - Single-leg deadlifts *For Balance/Proprioception:* - Single-leg stance - Wobble board - BOSU ball exercises - Sport-specific balance work ## Patellar Stability Bracing **Types:** - **Patellar tracking brace**: For initial recovery and return to sport - **Functional knee brace**: Some cases - **Sleeve with lateral support**: Common - **Custom braces**: For specific anatomy **When to Use:** - Initial recovery from dislocation - Return to sport phase - High-risk activities - Confidence building - Selected cases ## Long-Term Considerations **Recurrence Risk:** *First-Time Dislocator:* - 50% recurrence rate overall - Higher in young athletes - Lower in older patients - Depends on anatomic factors *With Proper Treatment:* - Conservative: 30-50% recurrence - Surgical: 5-15% recurrence - Better in adults than adolescents - Activity-dependent **Patellofemoral Arthritis:** *Risk Factors:* - Multiple dislocations - Cartilage damage from initial event - Inadequate treatment - Progressive deterioration *Long-Term:* - 25-50% develop arthritis over decades - Functional limitations possible - May need joint replacement eventually - Important consideration ## Sport-Specific Considerations **Return-to-Sport Decisions:** *Modify Sport:* - Some elite athletes change sports - Less cutting/pivoting demands - Recreation vs competition - Career considerations *Brace Use:* - Initial return to sport - High-risk activities - Confidence building - Patient preference *Continued Strengthening:* - Year-round maintenance - Sport-specific training - Address weaknesses - Long-term commitment ## When Surgery Is Best **Strong Indications:** 1. **Recurrent dislocations** (2+) 2. **Failed conservative treatment** 3. **Loose body** from osteochondral fracture 4. **Significant anatomic abnormalities** 5. **Elite athletes** with specific goals 6. **Symptom-limited** activities 7. **Patient preference** after counseling **Surgical Considerations:** - **Single procedure usually adequate** - **Multi-procedure** for complex cases - **Recovery typically 4-6 months** - **Outcomes generally good** - **Some long-term considerations** ## Critical Treatment Pearls **1. First-Time Treatment Matters** - Aggressive rehabilitation reduces recurrence - Address anatomic factors if possible - Don't rush return to sport - Patient education essential **2. Rehabilitation Is Critical** - Strength asymmetry predicts recurrence - VMO and hip strength essential - Functional progression important - Don't skip steps **3. Surgical Options Are Excellent** - Modern MPFL reconstruction reliable - Patient satisfaction high - Return to sport excellent - Recurrence rates low **4. Long-Term Monitoring** - Some develop arthritis - Activity modifications helpful - Strength maintenance important - Quality of life considerations **5. Anatomic Assessment** - TT-TG distance - Patella alta - Trochlear dysplasia - Plan accordingly ## Prevention **For First-Time Prevention:** - Address muscle imbalances - Build quad-hip strength - Sport-specific training - Proper technique - Recognize anatomic risk factors **For Recurrence Prevention:** - Complete rehabilitation - Surgical intervention when appropriate - Continued strengthening - Activity modifications if needed - Brace use during return - Long-term maintenance **Sport-Specific:** - Basketball: Cutting mechanics - Dance: Landing technique - Soccer: Pivot training - Gymnastics: Landing safety - All sports: Eccentric control ## When to Seek Specialist Care - All first-time dislocations - Recurrent dislocations - Failed conservative treatment - Anatomic concerns - Athletic patients - Need for return-to-sport planning - Concerns about long-term outcomes