Patellar malalignment

Definition

Patellofemoral malalignment

· disorder of static or dynamic relationship of patella and femur

· composed of patellar tilt and subluxation

Chondromalacia patellae

· pathological term describing softening of the articular cartilage of the patella

· may or may not be associated with patellar malalignment

Anterior knee pain

· syndrome of pain in the anterior knee usually referable to the patellofemoral joint

· often due to patellofemoral malalignment

Lateral patellar pressure syndrome

· anterior knee pain with tight tender lateral retinaculum

classification

Of patellar dislocations

· congenital

· habitual

· acute traumatic

· recurrent

Of anterior knee pain

· Fulkerson and Hungerford

· two criteria

1. malalignment

· I - subluxation

· II - subluxation and tilt

· III - tilt alone

· IV - no malalignment

2. articular lesion

· A - no articular lesion

· B - chondromalacia

· C - osteoarthritis

Aetiology

· may be due to

· acute trauma

· deficiencies of the extensor mechanism

· generalised ligamentous laxity

Deficiencies of the extensor mechanism

· may be

· congenital

· developmental

· acquired

Abnormalities of the patellofemoral articulation

· lateral patellar tilt

· patellar subluxation

· trochlear hypoplasia

· patella alta

Abnormalities of the supporting structures

· abnormality of vastus medialis

· atrophy

· high insertion

· laxity of medial retinaculum

· trauma

· generalised ligamentous laxity

· tightness of lateral structures

· vastus lateralis

· lateral retinaculum

· patellofemoral ligament

Malalignment of the extremity

· assessed by quadriceps angle

· can be increased by

· femoral neck anteversion

· internal femoral rotation

· external tibial rotation

· genu valgum

· lateral insertion of patellar tendon

Evaluation

Clinical assessment

History

· first dislocation

· age

· trauma

· subsequent dislocations

· mechanism

· frequency

· pain

· associated with flexed-knee activities

· eg. running, stair-climbing, sitting

· other problems

· giving way

· effusions

Examination

Alignment

· Q (quadriceps) angle

· line from anterior superior iliac spine to centre of patella

· line from centre of patella to tibial tuberosity

· angle subtended is Q angle

· normal range is 8-10^o in males and 12-15^o in females

· abnormal if > 15^o in males and > 20^o in females

· cause of abnormal Q angle

· femoral anteversion (squinting patellae)

· genu valgum

· external tibial torsion

Tracking

· observe path of patella during active and passive range

· J- sign

· patella sharply deviates laterally in terminal extension

Quadriceps

· quadriceps bulk

· esp. vastus medialis oblique

Tenderness

· lateral retinaculum

· retropatellar surface

Patellar tilt test

· evaluates tension of lateral restraint

· patient supine and relaxed with knees extended

· transepicondylar axis placed parallel to table

· lateral edge of patella elevated and medial edge depressed

· normal is 0-20^o tilt

· abnormal if unable to tilt it to horizontal

Patellar glide test (Sage sign)

· evaluates integrity and tension of medial and lateral restraints

· patient supine and relaxed with affected knee over other leg to maintain 30^o flexion of knee

· ability to translate patella medially and laterally assessed

· graded in number of quarter widths that patella displacable

· lateral

· normal is 0 to 2.5 quadrants

· > 3 quadrants is incompetent medial restraint

· medial

· normal is 1 to 2.5 quadrants

· < 1 quadrant is tight lateral restraint

· > 3 quadrants is hypermobile patella

Crepitus and grind

· evaluates articular cartilage

· patellofemoral crepitus on flexion and extension

· patellar grind

· pain on compression of the patella

· patella compressed into trochlea

· patella either moved from side to side or patient asked to contract quadriceps

Apprehension test

· patient supine and relaxed

· patella pushed laterally while knee flexed 30^o

· positive if patient uncomfortable (pain or apprehension)

Generalised ligamentous laxity

· positive if 4 or more of 5 signs

Radiological assessment

Lateral tilt

· Laurin’s lines

· tangential x-ray with knee flexed to 20^o

· line along lateral patellar facet

· line between most prominent anterior points of trochlea

· lines should diverge

Subluxation

· Merchant views (congruence angle)

· tangential x-ray with knee flexed to 45^o

· line bisecting sulcus angle

· line from sulcus to lowest point of patella

· angle between lines should be < 16^o

Trochlear hypoplasia

· Merchant views (sulcus angle)

· tangential x-ray with knee flexed to 45^o

· measure sulcus angle of femoral groove

· > 140^o is flattened

Patella alta

· Insall’s ratio

· lateral x-ray with knee flexed to 30^o

· patellar length:patellar tendon length

· > 1.2 is abnormal

· Blumensaat’s line

· knee flexed to 30^o

· line along intercondylar notch

· line should just touch inferior pole of patella

Osteoarthritis

· of the patellofemoral joint

questions

· is the pain due to the patellofemoral joint ?

· is the pain articular or retinacular ?

· is there malalignment ?

· is it tilt or subluxation ?

· are the restraints too loose or too tight ?

patterns

Patellar subluxation (= instability)

· often have transient lateral displacement

· complain of instability

· increased risk of dislocation

· excessive lateral glide

· positive apprehension test

· increased congruence angle

· osteoarthritis not common

Patellar tilt (= arthritis)

· have chronic altered articular pressure in the groove

· complain of pain

· tight lateral retinaculum

· tender lateral retinaculum

· abnormal patellar tilt test

· increased tilt on x-ray

· usually have chondromalacia

· often develop arthritis

Patellar tilt and subluxation

· combination of instability and arthritis

Anterior knee pain without malalignment

· may or may not have articular degeneration

Management

Nonoperative

· 90% respond

· behaviour modification

· analgesia / anti-inflammatories

· physiotherapy

· stretching of hamstrings, iliotibial band and retinaculum

· quadriceps strengthening (esp. vastus medialis oblique)

· patellar taping

Operative

Principles

· for failure of nonoperative treatment

· little benefit for pain with normal alignment

· more than 100 techniques described

Arthroscopy

· first step

· document degenerative changes

· grading system described by Outerbridge

· I - cartilage softening

· II - fibrillation < 1/2” diameter

· III - fibrillation > 1/2” diameter

· IV - exposed bone

· debride loose articular cartilage

Patellar subluxation

· realignment

Patellar tilt

· lateral release

Patellar tilt and subluxation

· lateral release if little or no chondromalacia

· add anteromedial transfer of tibial tubercle if osteoarthritis

Patellar osteoarthritis

· anterior or anteromedial transfer of tibial tubercle to decompress joint

Arthroscopic debridement

· removal of loose fragments

· decreases shedding into joint

· decreases inflammatory response

· beneficial

· patellar shaving

· of no detectable benefit

Lateral release

Indications

· PF pain with lateral tilt

· lateral retinacular pain with lateral tilt or subluxation

· PF pain with tight lateral retinaculum

Contraindications

· significant PF osteoarthritis

· normal tracking patella

Techniques

· open release

· percutaneous release

· arthroscopic release

Important points

· divide retinaculum within 1 cm of patella

· cauterise superior geniculate vessels

· obtain haemostasis

· must be able to evert patella 90^o at end

· aggressive rehabilitation postoperatively

Results

· good or excellent results in 90%

· most common complication is haematoma

Proximal realignment

· realignment of quadriceps muscle on patella

· together with lateral release

Madigan procedure

· vastus medialis oblique detached

· advanced laterally and distally

· sutured to fascia on patella

Insall procedure

· lateral release performed

· medial parapatellar incision made

· medial flap advanced distally and laterally by overlapping and suturing medial flap 1 cm over lateral flap

Distal realignment

Indications

· PF subluxation or dislocation with increased Q angle

· PF arthritis with increased Q angle

Contraindications

· open physes

· normal Q angle

Techniques

· Hauser procedure

· tibial tuberosity moved medially and posteriorly

· increases PF pressure and causes late osteoarthritis

· Roux-Goldthwaite procedure

· lateral half of patellar tendon detached

· transferred beneath intact medial half

· sutured to medial tibia (to insertion of sartorius)

· Elmslie-Trillat procedure

· tibial tuberosity moved medially

· bone graft inserted medially

· Maquet procedure

· tibial tuberosity moved anteriorly

· bone graft packed underneath

· anteromedial transfer

· long oblique osteotomy to move tibial tuberosity medially and forward

Combined

3 in 1 procedure

· lateral release performed

· medial plication as above

· medial 1/3 of patellar tendon detached

· sutured medially to MCL

Patellectomy

· final procedure if other options fail

· extensor mechanism needs to be aligned to avoid subluxation of repair

Patellar dislocation

congenital

Definition

· laterally displaced patella

· never has been in reduced position

· remains dislocated and cannot be reduced

Epidemiology

· often familial

· may be bilateral

Aetiology

· associated with

· abnormal quadriceps mechanism

· small misshapen patella

Clinical

· difficult to diagnose

· often not detected until age 3 or 4

· flexion contracture of knee

· genu valgum

· externally rotated tibia

· patella remains on anterolateral aspect of thigh

· quadriceps mechanism laterally displaced

Treatment

· surgical

· principle is to centralise quadriceps mechanism

· medial plication

· lateral release

· distal realignment

· hamstring release

· condyloplasty

· results unpredictable

Acute traumatic dislocation

Aetiology

· direct laterally-directed blow to patella

· usually with knee partly flexed and quadriceps relaxed

Clinical findings

· history of

· collapse and fall to ground with injury

· no active or passive movement of knee possible

· laterally-displaced patella which was reduced

· tenderness of medial patella and retinaculum

· positive apprehension test

X-ray findings

· increased lateral patellar shift

· osteochondral fracture (5%)

Nonoperative treatment

· options

· cast for 6 weeks

· splint until comfortable then rehabilitation

· recurrent dislocation rate

· 40% with cast

· 20% with rehabilitation

Operative treatment

Indications

· young athlete

· history of major trauma

· signs of significant injury

· large haemarthrosis

· osteochondral fracture

· signs of malalignment

Operative findings

· medial capsular tear

· usually from femur

· fractures or chondral damage

· medial margin of patella

· lateral femoral condyle

Treatment

· arthroscopy

· debridement or fixation of fractures and chondral damage

· repair of medial capsule

· lateral release if tight

· brace in extension for 3 weeks

Results

· 10% redislocation rate

recurrent

Definition

· repeated dislocation of patella with minimal trauma

Epidemiology

· more common girls

· often bilateral

Aetiology

· predisposition as for patellar malalignment

· acute trauma

· deficiencies of extensor mechanism

· generalised ligamentous laxity

Clinical features

Dislocation

· dislocation occurs unexpectedly when quadriceps contracted with knee in flexion

· always dislocates laterally

· may be prominence of uncovered medial condyle

· medial tenderness and effusion

Interval

· may be anterior knee pain or instability

· features of malalignment

treatment

· of patellar malalignment