Patella Dislocation

Lower Limb

Overview

Patella dislocation occurs when the patella displaces from the trochlear groove, most commonly in a lateral direction, typically resulting from direct trauma, sudden deceleration, or underlying anatomical predisposition. This acute injury causes severe pain, swelling, and mechanical instability, and often reduces spontaneously but requires careful assessment to rule out associated osteochondral fractures and soft tissue damage. Recurrent dislocation is common (30-50% of cases) and may necessitate surgical intervention.

Pathophysiology

The patella normally articulates within the femoral trochlear groove, stabilized by the vastus medialis obliquus (VMO), patellar ligaments, and medial patellofemoral ligament (MPFL). Dislocation typically results from lateral displacement caused by direct blow, sudden valgus stress with external rotation, or chronic biomechanical factors including increased Q-angle, femoral anteversion, trochlear dysplasia, patella alta, and vastus medialis weakness. The acute dislocation disrupts the MPFL and can damage articular cartilage, creating subsequent instability and osteoarthritic changes.

Patient Education

Patella dislocation is a serious knee injury requiring immediate professional assessment and conservative or surgical management; early rehabilitation focusing on VMO strengthening and proprioception is critical to prevent recurrence.

Typical Presentation

Site

Anterior knee, particularly laterally displaced patella; often lateral compartment involvement on reduction

Quality

Acute sharp, stabbing pain; mechanical catching or locking sensation; immediate sharp pain at moment of dislocation

Intensity

Severe acute pain (8-10/10) during dislocation; moderate to severe (5-8/10) post-reduction with significant swelling

Aggravating

Weight-bearing and walking post-injury; attempting to extend the knee; pivoting movements; stairs (especially descending); flexion-extension cycling

Relieving

Knee immobilization; rest and ice application; knee flexion positions; elevation; anti-inflammatory medications

Associated

Immediate swelling (haemarthrosis); apprehension and fear; effusion; knee instability; difficulty bearing weight; quadriceps inhibition; associated ligamentous or osteochondral injuries; lateral knee tenderness

Orthopaedic Tests

Apprehension Test (Crank Test)

Procedure

Patient supine with knee flexed to 70–90°. Examiner externally rotates the tibia and applies valgus stress to the knee while observing for apprehension that the patella will dislocate laterally.

Positive Finding

Patient reports apprehension or fear that the patella will slip out of place, particularly with external tibial rotation and valgus stress.

Sensitivity / Specificity

72% / 97%

Thomee et al., 1996, Knee Surgery, Sports Traumatology, Arthroscopy

Interpretation

High specificity suggests a positive apprehension test strongly indicates lateral patellar instability or risk of recurrent dislocation. Apprehension is more clinically meaningful than pain alone.

J-Sign (Dynamic Patellar Tracking)

Procedure

Patient supine with knee extended. Examiner or patient actively flexes the knee to 90° while observing patellar tracking from Q-angle perspective. Patella demonstrates lateral deviation followed by medial tracking ('J' pattern).

Positive Finding

Patella deviates laterally in early flexion (0–30°) then corrects medially ('J'-shaped trajectory), or maintains lateral deviation throughout.

Sensitivity / Specificity

null / Unknown

Interpretation

Suggests patellar tracking disorder and lateral patellar instability. Not a definitive diagnostic test but clinically useful for identifying dynamic instability patterns.

Patellar Glide Test

Procedure

Patient supine with knee in full extension and quadriceps relaxed. Examiner manually translates the patella medially and laterally, measuring displacement in quadrants relative to patellar width.

Positive Finding

Lateral glide >2 quadrants (>50% patellar width) or apprehension during passive lateral glide; asymmetry compared to contralateral knee.

Sensitivity / Specificity

null / Unknown

Interpretation

Excessive lateral mobility suggests capsular laxity and lateral patellar instability. Used to quantify passive stability; does not definitively predict dislocation risk but identifies hypermobility.

Pivot Shift Test (for Patella)

Procedure

Patient supine. Knee passively flexed to 90° with foot internally rotated and valgus stress applied. Examiner then extends the knee while maintaining valgus and internal rotation, observing for sudden lateral patellar subluxation during extension.

Positive Finding

Sudden lateral shift or clunk of the patella during knee extension under valgus and internal rotational stress; patient reports apprehension.

Sensitivity / Specificity

null / Unknown

Interpretation

Reproduces dynamic instability mechanism and suggests significant ligamentous laxity (MPFL insufficiency). Difficult to perform but highly specific when positive.

Medial Patellofemoral Ligament (MPFL) Palpation & Stress Test

Procedure

Patient supine with knee flexed to 20–30°. Examiner palpates the MPFL (running from medial femoral epicondyle to patella). Simultaneously apply valgus stress or passive lateral patellar translation to stress the ligament.

Positive Finding

Tenderness along MPFL course; increased pain or apprehension with valgus stress and lateral patellar translation; palpable gap or thickening suggesting acute or chronic ligament injury.

Sensitivity / Specificity

Unknown / Unknown

Interpretation

MPFL is primary restraint to lateral patellar dislocation. Positive findings suggest MPFL insufficiency, a key pathology in recurrent patellar dislocation.

Q-Angle Measurement

Procedure

Patient supine with knee extended and hip relaxed. Draw line from anterior superior iliac spine to patella center, and second line from patella center to tibial tubercle. Measure the angle between these lines.

Positive Finding

Q-angle >20° (normal <15°); asymmetry >3° compared to contralateral side.

Sensitivity / Specificity

Unknown / Unknown

Interpretation

Elevated Q-angle increases lateral patellar tracking tendency and dislocation risk by increasing valgus vector. Contextual measure; high Q-angle is risk factor but not diagnostic alone.

⚠ Red Flags

  • •Severe uncontrolled pain suggesting associated fracture or vascular compromise
  • •Signs of vascular compromise: absent distal pulses, severe pallor, cold limb
  • •Neurovascular compromise: foot numbness, severe paresthesia, motor weakness
  • •Inability to reduce patella or patella remains dislocated (requires urgent orthopaedic intervention)
  • •Evidence of significant osteochondral fracture on imaging
  • •Gross knee instability suggesting multi-ligamentous injury
  • •Signs of compartment syndrome: severe pain disproportionate to injury, pain with passive stretch

⚡ Yellow Flags

  • •High anxiety and fear-avoidance related to re-dislocation risk
  • •Catastrophic thinking about knee stability and future function
  • •Previous psychological trauma or anxiety disorders affecting rehabilitation adherence
  • •Occupational demands requiring high-demand pivoting activities
  • •Poor motivation or inconsistent rehabilitation participation
  • •Social isolation or lack of support for recovery process

Osteopathic Techniques

Region

Vastus medialis obliquus and quadriceps

Technique

Soft Tissue

Rationale

Direct soft tissue mobilization to VMO addresses muscular inhibition and promotes recruitment of this critical dynamic stabilizer; improves muscle activation patterns essential for medial patellar stability post-injury

Region

Hip abductors and external rotators

Technique

MET

Rationale

Muscle energy techniques targeting gluteus medius and piriformis improve hip stability and reduce femoral internal rotation contributing to lateralizing forces on patella; addresses kinetic chain dysfunction

Region

Knee joint and ligamentous structures

Technique

Functional

Rationale

Functional techniques support healing of damaged MPFL and patellofemoral joint structures by promoting proprioceptive awareness and gentle movement within pain-free range; facilitates neuromuscular control

Region

Patellar tracking and tibiofemoral joint

Technique

Articulation

Rationale

Gentle articulation in pain-free ranges promotes synovial fluid circulation, reduces stiffness, and maintains joint mobility during healing phase without compromising ligamentous repair

Region

Hip flexors and tensor fasciae latae

Technique

Soft Tissue

Rationale

Soft tissue release of hip flexors reduces anterior pelvic tilt and medial tibial rotation; TFL tension reduction decreases lateral pull on patella through iliotibial band biomechanical coupling

Region

Ankle and foot proprioceptive structures

Technique

Soft Tissue

Rationale

Early proprioceptive activation through ankle mobilization improves lower kinetic chain feedback mechanisms, supporting proximal stability deficits and reducing compensatory stress on recovering patellofemoral joint

Add-On Approaches

Chinese Medicine

Acupuncture targeting local points (Liangqiu ST34, Xiyangguan GB33, Dubi ST35) and distal points (Yanglingquan GB34) to reduce swelling and pain; moxibustion to support blood circulation in chronic post-injury phase; herbal anti-inflammatory support

Chiropractic

High-velocity low-amplitude manipulation of patellofemoral joint (if appropriate post-acute phase) to restore segmental mobility; assessment of pelvic and spinal alignment affecting kinetic chain; ART/Graston techniques for VMO and soft tissue restrictions

Physiotherapy

Progressive quadriceps strengthening emphasizing VMO activation; proprioceptive training and balance work; functional movement training including step-ups, lateral stepping, and controlled pivoting; neuromuscular re-education for patellar tracking

Remedial Massage

Remedial massage of VMO, adductors, and hip internal rotators to enhance muscle activation; targeted release of vastus lateralis and ITB to reduce lateral pulling forces; cross-friction techniques to promote MPFL healing in subacute phase

Rehabilitation Exercises

Supine Knee Flexion-Extension (Controlled Pendulum)

Range of MotionBeginner

Quadriceps Sets with VMO Emphasis (Towel Roll or Biofeedback)

StrengtheningBeginner

Supine Hamstring Stretch (Static)

StretchingBeginner

Seated Short-Arc Quadriceps (SAQ) with Biofeedback

BalanceBeginner

Supine Hip Abduction (Legs Apart) to Promote VMO Activation

PosturalBeginner

Clam Shells (Side-Lying Hip Abduction and External Rotation)

StrengtheningIntermediate

Supine Glute Bridge (Bilateral, Progressing to Single-Leg)

StrengtheningIntermediate

Single-Leg Stance on Stable Surface (Supported)

BalanceIntermediate

Lateral Step-Ups (Low Height, Controlled)

StrengtheningIntermediate

Tandem Standing or Tandem Walking (Heel-Toe Line)

BalanceIntermediate

Forward Lunges with Controlled Descent (Emphasis on VMO and Hip Stability)

StrengtheningAdvanced

Single-Leg Stance on Unstable Surface (Foam Pad or Balance Disc)

BalanceAdvanced

Referral Criteria

  • •Patella remains dislocated or cannot be reduced by healthcare professional
  • •Evidence of significant osteochondral fracture on imaging requiring orthopedic evaluation
  • •Signs of vascular or neurovascular compromise requiring urgent vascular assessment
  • •Multiple recurrent dislocations (typically 3+ episodes) despite conservative management, suggesting surgical intervention candidate
  • •Severe associated ligamentous injury (ACL, PCL, MCL tears) requiring specialist orthopedic assessment
  • •Failure to progress with conservative management after 12 weeks despite adherence
  • •Chronic instability or apprehension limiting functional activities despite 6+ months rehabilitation
  • •Underlying anatomical factors (significant trochlear dysplasia, severe Q-angle) requiring surgical consultation
  • •Significant osteoarthritic changes on imaging requiring specialist joint management