Patellar Dislocation

What are the 2 bony restraints of the patella?

• Femoral trochlear groove

• Patellofemoral articular cartilage

What are the 4 soft tissue restraints of the patella?

• Quads tendon

• Patellofemoral ligament: medial & lateral

• Patellotibial ligaments: medial & lateral

• Retinaculum

List risk factors for patellar dislocation

• LE malalignment

• Femoral-tibial angle & rotation

• Static & dynamic Q angle

• Tibial tuberosity trochlear groove distance

• Trochlear dysplasia

• Patella alta

• Medial patellofemoral ligament & lateral retinaculum (static)

• Quads & hip abductors (dynamic)

What is the primary restraint to lateral translation of patella?

Medial patellofemoral ligament

When close to full extension (0-30°), what is the patella restrained by?

Soft tissue

When the knee is flexed >30°, what happens to the patella?

• It reduces in the trochlear groove

• Stabilized by bony restraints

What are the medial passive patellar stabilizers?

• Medial patellofemoral ligament

• Medial patellotibial ligament

• Medial patellomeniscal ligament

• Medial joint capsule

What are the 2 components of the medial patellofemoral ligament?

• Transverse → b/w adductor tubercle & MFC

• Oblique → MCL

What are the active medial patellar stabilizers?

• VMO & blends w/ medial patellofemoral ligament

• Gracilis

• Semitendinosus

• Adductor magnus

List the patient profile of patellar dislocations.

• Active young individuals

• Females > males

• Adolescents → young adulthood

• Higher recurrence in females

Why do most patellar dislocations occur between 0–30° of knee flexion?

Because the patella has minimal bony stability and relies mainly on soft tissue restraints, especially the MPFL.

In what position does a patellar dislocation most commonly occur?

With the knee in inner-range flexion (about 20–30°)

In what direction does the patella dislocate most frequently?

Laterally

What structure does the dislocated patella impact?

The WB surface of the lateral femoral condyle

Why is the patella susceptible to chondral injury during a dislocation?

Because its convex articular surface

What causes cartilage injury to the lateral femoral condyle during patellar dislocation?

Impaction and shearing forces from the patella moving against a fixed femur

When does a femoral bone bruise occur after a patellar dislocation?

During reduction of the patella with knee extension

What 2 structures are also damaged with patellar dislocations?

• Medial patellofemoral ligament

• Medial retinaculum

What are the goals for rehab for patellar dislocations?

• Protect damaged tissues

• Reduce hemarthrosis

• Reduce pain

• Restore knee ROM

• Restore quads strength & bulk

• Prevent patellar instability & recurrent dislocation

What is the period of immobilization after patellar dislocation?

2 - 6 weeks depending on severity

What interventions are used when treating patellar dislocations?

• Immobilization initially

• Quad strengthening

• Improve LE stacking in kinetic chain

• Taping to decrease symptoms

• Bracing to increase compression/stabilization

Are lateral releases (surgery) for patellar dislocations favored?

NO; do not use anymore

List the 4 indications for surgical intervention for patellar dislocation.

• Presence of chondral lesion or osteochondral body

• Rupture of medial stabilizers

• Persistent laterally subluxed patella

• Secondary dislocation of patient with malalignment or dysplasia

What are the 2 common surgical procedures used to treat patellar dislocations?

• Reconstruction of medial structures

• Distal realignment

What are the goals of MPFL Reconstruction rehab during phase 1 (0-6 weeks)?

• Protect surgery

• Full passive knee extension within 2 weeks

• 90° active knee flexion by 6 weeks

What are the precautions of MPFL Reconstruction rehab during phase 1 (0-6 weeks)?

• WBAT w/ crutches w/ post-op brace locked in extension

• Avoid rotational movement through knee & LE

What are therex of MPFL Reconstruction rehab during phase 1 (0-6 weeks)?

• ROM (give manual lateral patellar stabilization with 1st initiation of ROM)

• Quad strengthening with NMES

What are the precautions of MPFL Reconstruction rehab during phase 2 (6 weeks)?

• Avoid over-stressing graft (caution w/ rotational movement)

• Patients w/ patellar of trochlear chondroplasty or cartilage defect avoid excessive or abnormal PF joint stress during open and closed chain loading

• Avoid post-activity swelling

• No impact

What are therex of MPFL Reconstruction rehab during phase 2 (6 weeks)?

Continue functional CKC strengthening avoiding dynamic valgus or medial knee displacement

What are therex of MPFL Reconstruction rehab during phase 3 (12-16 weeks)?

• Initiate low amplitude agility drills in sagittal & frontal plane

• Avoid transverse plane while in frontal plane

• Impact control exercises in sagittal & frontal planes

• Initiate running progression once pt has good SL control & tolerance to bounding

What are therex of MPFL Reconstruction rehab during phase 4 (20 weeks)?

• Progress impact control to 1 foot same foot hopping

• Movement control exercises begin with low velocity, single plane activities, & progressing to higher velocity & multiplanar activities

• Sport/work specific balance & proprioception skills

What criteria need to be met for Phase 4 patients to return to sport/work?

• >90% on jump testing & all 4 functional hop tests

• Dynamic NM control with multiplanar activities and without pain, instability, or swelling

• Pt confidence in return to sport

What are the 2 traumatic MOIs of patellar fractures?

• Fall onto patella

• MVA

What are the 2 iatrogenic MOIs for patellar fractures?

• Post ACL IPT reconstruction

• TKA

What is the conservative treatment for patellar fractures?

Immobilization

What are the surgical interventions used to treat patellar fractures?

• Fixation

• Pallectomy

What criteria indicate a surgical fixation of a patellar fracture?

• Articular step-off >2mm

• >3mm of displacement

• Open fractures

What is the most common surgical fixation of a patellar fracture?

Tension band construct fixation

How are knee braces utilized for post-op rehab in phases 1-3?

• Phase 1 = immobilizer (locked hinge)

• Phase 2 = worn w/ WB

• Phase 3 = Unlocked, worn during WB

What is the WB progression from phase 1-3 of post-op rehab?

• Phase 1 = WBAT w/ knee locked in extension

• Phase 2 = WBAT w/ knee locked in extension

• FWB

What is the ROM progression from phase 1-3 of post-op rehab?

• Phase 1 = 0-30° of PROM, AAROM, & AROM

• Phase 2 = add 15° of flexion/week (goal = 90° by 6 weeks)

• Phase 3 = Full ROM by week 10

What is the therex progression from phase 1-3 of post-op rehab?

• Phase 1 = isometrics (quads, HS, hip) & NMES

• Phase 2 = isometrics (quads, HS, hip) & initiate SLR

• Phase 3 = squats, bridges, hip 4-way, SLR, proprioception