Acute Knee Injuries

MOI contusion

direct contact

S/sx for contusion

pain, swelling, point tenderness, and discoloration

Pathology of ACL injury

Anterior translation of the tibia in relation to the femur causing a tear of the ACL

MOI of ACL injury

Contact -
hit in back of leg (+ pushed into valgus)
hit anterior femur when planting and force tibia anteriorly
Non-contact:
planting and cutting (knee falling into valgus). When decelerating, quads are eccentrically lengthening, giving room for the tibia to move

S/sx of ACL injury

Effusion, instability, hear a pop (grade 3), or deep pain

Pathology of PCL injury

Posterior translation of the tibia relative to the femur

MOI of PCL injury

Anterior blow to the tibia from falling on a flexed knee
Hyperflexion or hyperextension

S/sx of PCL injury

Effusion, instability, hear a pop (grade 3), or deep pain in back of knee

MOI of MCL injury

contact or non-contact injury
Valgus force

S/sx of MCL injury

Pain, mild-moderate swelling, point tenderness over MCL (potentially in joint line if injury to medial meniscus too)

MOI of LCL injury

Contact or non-contact
Varus force

S/sx of LCL injury

Pain, mild-moderate swelling, and point tenderness over LCL

What are the 4 purposes of the meniscus?

1. menisci stabilize joint by deepening the joint surface
2. act as shock absorbers
3. lubricate the joint
4. improve weight distribution

Pathology of meniscus injury

Tear in the meniscus
Most common is longitudinal or bucket-handle tear

MOI of meniscus injury

Compression and rotation of the femur on a fixed tibia

S/sx of meniscus injury

Instability, locking, catching, clicking, joint line tenderness

MOI of patellar tendon rupture

Violent, rapid quad contraction

S/sx of patellar tendon rupture

Pop, patella sits superior, or palpable gap between patella and tibial tuberosity

MOI patella fracture

Fall on flexed knee
Severe traction caused by a forceful quadriceps contraction

S/sx of patella fracture

Immediate and severe pain
Unwillingness to contract quads
Rapid swelling

MOI of patellofemoral subluxation/dislocation

Direct blow to medial patella

What are the risk factors of patellofemoral subluxation/dislocation

Shallow femoral groove (trochlea dysplasia)
Excessive Q-angle (ASIS, patella, and tibial tuberosity)
Hypermobile patella
Weak VMO (VLO is stronger, pulling patella laterally)
Patella alta

S/sx of patellofemoral subluxation/dislocation

Pain, pop, deformity, palpable tenderness over medial border, and anterior knee swelling