Meniscus and ligament knee injuries

Background

- torn menis or lig can cause sig disability, so expeditious repair needed

- knee largest articulating joint in body- is modified hing with extensive ROM

- stability provided by sof tissue- cruciate ligs and collateral

ligs, menisci, capsule and muscles

- acl and pcl add stability and proprioception

- ligs passively limit motion therfore providing stability

- acl- pcl limit ant and post desplacement of tibia on femur respectivelly

- acl limits ant motion of tibia on femur- if tibial plateau keeps going forward get relative int rotation of tibia at terminal extention and can result in sensation knee is buckling or giving out- most common during pivoting.

- acl inj also gives "loss of confidence" due to lack of proprioception input.

- pcl provides stability regardless of position of knee- if disrupted, tibia goes posteriorly- may get hyperextension of knee, post displacement of tibial during flexing and varus and valgus angulation with knee extenstion.

- symptomatic pcl inj more common in pt with chronic tear or acute tear with other lig inj

- Meniscus- increase joint stability, nutrition, lubrication, shock absorption or articular cartilage.

- lat meniscus larger and less firmly attached- more mobile

- medial menis immobilie and attached to MCL and capsule

- med menis greater chance of inj since bears more weight and immobile

- knee flexion pushes menisc posteriorly

MECHANISMS OF INJ

- position of knee at time of inj dictates which structures inj

- acl- inj during traumatic twisting with valgus stress- may hear pop

- pcl- foot planted, twist with force directed posteriorly against tibia with knee flexed

- col lig- from abduction and ext rotation

- with age menisc tissure degenerates and splits and get horizontal tears- this leads to more loads on articular cartilage and arthritis.

- menisc are without pain fibres so pain from tearing and bleeding into perif attachments and capsule that causes pain.

- locked knee in flexed position by bucket handle tear in mcl- more common in youger pt

- lcl more mobile so less locking when torn- may get clicking

- women have more acl inj than men

Diagnosis

- examine healthy knee first- relaxes pt and ensures trust. also needed for comparison

- inspection- gait- effusion

- palpation- warmth, eff, swelling, crepitance

1. function-
   1. ACL tests
      1. lachman, ant drawer and lat pivot shift- should not cause pain in subacute setting Lachman- pt supine, knee 20- 30' extended- hold dista femur with one hand and prox tibia with other and pull up- should feed discreet stop- is positive test if no stop felt or too much motion
      2. Ant Drawer- pt supine, knee flexed 90', pull up on prox tibia
      3. Lateral Pivot Shift- valgus stress to knee with twisting force while flexing knee. one hand on lat part of knee pushing in. other hand on foot with lateral force. As start to extend knee, will get thud or jerk at 10- 20' representing ant subluxation of tibia on femur
   2. pcl stability
      1. post drawer test
         1. pt supine, both knees flexed 90'. In knee with pcl tear tibia will sag posteriorly. If putting force on post calf corrects sag is positive test.
   3. Meniscal integrity
      1. McMurray
         1. pt supine, one hand on foot, other gives valgus force to knee- extend knee and int and ext rotating tibia. Positive if get popping, sensation of symptoms along joint line and inablity to extend knee fully.
      2. Apley Compression test
         1. pt prone, put your knee on pts thigh and flex knee and ext rotate tibia- then compress tibia downward- if more pain is postive
      3. Medial Lateral Grind
         1. supine, cradle calf in one hand. other on tibial joint line- apply varus and valgus stresses during flex and extending knee. if get grinding sensaiton from hand on joint line if positive

RESULTS

- composite test of acl, pcl meniscus reasonable sens and specific.

acl/ pcl test better predictors than menisc tests.

- no data to judge test for mcl/ lcl inj

Source

6/06 MISTRY