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 a direct blow or a sudden valgus twist with external rotation. 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

Test descriptions are written with AI assistance from standard clinical texts. Where a test lists Sources, its description has been checked against them; those sources are independent and do not endorse OsteoKit. Accuracy figures and grades (A–D) appear only when checked against the published study; tests without one are marked “No accuracy study”.

Further reading: full test procedures are described in standard clinical examination texts, e.g. Magee & Manske, Orthopedic Physical Assessment (7th ed.), and Cook & Hegedus, Orthopedic Physical Examination Tests: An Evidence-Based Approach (2nd ed.).

No accuracy study

Patellar Apprehension Test (Fairbank)

Procedure

Patient supine, knee bent to about 20–30° over your thigh, quadriceps relaxed. Gently push the kneecap outwards.

Positive Finding

The patient shows apprehension, tightens the quadriceps or pushes your hand away.

Interpretation

A positive test supports lateral patellar instability. The moving patellar apprehension test, which moves the knee through flexion and extension while pushing the kneecap outwards then inwards, is a more informative version. This entry previously described a different manoeuvre. Note: the static apprehension ("crank") test has limited and variable accuracy. The validated variant is the moving patellar apprehension test (Ahmad CS et al., Am J Sports Med 2009; PMID 19193601), which reported 100% sensitivity and 88% specificity against examination under anaesthesia — worth adding as a distinct test.

Sources

No accuracy study

J-Sign (Dynamic Patellar Tracking)

Procedure

Patient seated with the lower leg hanging. Ask the patient to straighten the knee slowly while you watch the kneecap from the front.

Positive Finding

The kneecap moves suddenly outwards near full extension, tracing an upside-down J.

Interpretation

Suggests maltracking, often with a high-riding kneecap or a shallow trochlea, which increases the risk of recurrent dislocation. Specialist imaging assesses these features.

Sources

No accuracy study

Patellar Glide Test

Procedure

Patient supine, knee bent to about 20–30°, quadriceps relaxed. Divide the kneecap mentally into four vertical quarters and glide it outwards and inwards, estimating how many quarters it moves. Compare with the other side.

Positive Finding

Clearly more lateral movement than on the other side, or apprehension.

Interpretation

Excess lateral glide suggests a lax or torn medial patellofemoral ligament. Many people have lax kneecaps without symptoms, so compare sides and interpret with the history.

Sources

No accuracy study

Patellar Instability Provocation (Not a Recognised Test)

Procedure

Not a recognised test. Use the patellar apprehension test, the moving patellar apprehension test and the J-sign instead.

Positive Finding

Not applicable.

Interpretation

The pivot shift is an ACL test for the tibia, not the kneecap. This entry is a candidate for removal.

Further reading

No accuracy study

Medial Patellofemoral Ligament (MPFL) Palpation & Stress Test

Procedure

Patient supine, knee slightly bent. Palpate along the MPFL from the inner edge of the kneecap to its femoral attachment near the adductor tubercle, then gently glide the kneecap outwards.

Positive Finding

Tenderness along the ligament, especially at the femoral attachment, with pain or apprehension on lateral glide.

Interpretation

Supports an MPFL injury, which occurs in most first-time patellar dislocations. A large bloody effusion after a dislocation may mean a cartilage or bone fragment, which needs imaging and orthopaedic referral.

Sources

Measurement

Q-Angle Measurement

Procedure

Patient supine, legs straight, quadriceps relaxed. Draw a line from the ASIS to the centre of the kneecap and from the centre of the kneecap to the tibial tuberosity; measure the angle between them. Compare sides.

Positive Finding

A larger angle on one side, or a larger angle than expected.

Interpretation

Describes alignment only. In a dislocated or unstable kneecap the measurement can be misleading because the kneecap sits outwards. Specialists use imaging measures instead.

Sources

⚠ 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

After a first-time dislocation with no loose body or joint damage, care is conservative: pain relief, a short spell in a brace, then physiotherapy for quadriceps (VMO) and core strength and balance.

Safety: An acute dislocation needs prompt reduction, then X-rays (including a sunrise view) to look for a fracture or loose body before rehab starts.

Region

Vastus medialis obliquus and quadriceps

Technique

Soft tissue, knee and quadricepsNo trials found

Rationale

Hands-on work to the quadriceps and the tissues around the knee to ease tension and pain.

How it's done & evidence

How it's done

Hands-on kneading, stroking and sustained pressure to the quadriceps, the patellar and quadriceps tendons, the iliotibial band near the knee and the tissues around the joint. Transverse friction massage across a tendon is one form. In trials it was given alongside exercise.

Evidence in Patella Dislocation

Searched 24 Oct 2026: no trials of soft tissue technique in patellar dislocation.

Region

Hip abductors and external rotators

Technique

Muscle energy, hip and thigh musclesNo trials found

Rationale

Low-force, patient-powered stretch for tight hip and thigh muscles.

How it's done, cautions & evidence

How it's done

The muscle (for example the hamstrings, adductors or rectus femoris) is taken to its barrier. The patient pushes gently, at about 10–20% effort, against resistance for 5–10 seconds, relaxes for 3–5 seconds, and the new barrier is taken up.

Cautions

Not used with an acute fracture, a joint infection or a bone malignancy; take care with severe osteoporosis or after surgery that limits muscle contraction. Use the least force needed: too much can tear a muscle or pull off a tendon, especially in older patients.

Evidence in Patella Dislocation

Searched 24 Oct 2026: no trials of hip muscle energy technique in patellar dislocation.

Region

Hip flexors and tensor fasciae latae

Technique

Soft tissue, hip and thighNo trials found

Rationale

Eases tension in the hip and thigh muscles that help control knee alignment.

How it's done & evidence

How it's done

Hands-on kneading, stretching and sustained pressure to the muscles around the hip and thigh: the hip flexors, adductors and hamstrings, and tensor fasciae latae with the iliotibial band.

Evidence in Patella Dislocation

Searched 24 Oct 2026: no trials of hip soft tissue technique in patellar dislocation.

Sources

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