The Knee Flashcards
What is the strongest bone in the body?
The femur
What is the function of the patella?
It is a sesamoid bone that acts as a pulley, improving the angle of pull (Q angle)
What nerve innervates the extensors?
femoral nerves
What nerve innervates the flexors?
sciatic nerve
What must occur in order to internally or externally rotate the knee?
Knee must be flexed at least 20 degrees
MCL Injury
- MOI
- PE
- Rad
- MR
MOI
- valgus stress to knee
PE
- place knee off table and load to find instability
Rad
- chronic MCL sprains may show calcification on plain films
- MR is rarely needed but helpful if injury to ACL is suspected
LCL Injury
- MOI
- PE
MOI
- varus force
PE
- test with 30 degrees of flexion to negate ACL and PCL resistance
MCL and LCL tx
RICE Immobilize Non-operative care is mainstay Scar heals in 6 weeks to one year Combined ACL/MCL injuries or complete LCL disruption require MR and possible repair
Types of Meniscal Tears
Bucket handle
Horizontal
Longitudinal
Radial
Bucket Handle Tear
- commonly associated with
- symptoms
- MRI
- Tx
Commonly associated with
- MC medially
- frequently associated with ACL tears
Symptoms
- can intermittently lock
- comes and goes
MRI
- Double PCL sign
Tx
- closed reduction temporarily until can get fixed
- arthroscopic resection
ACL Injuries
- MOI
- PE
- Rad
- Tx
MOI
- young pts MC in football and basketball
- from shearing forces on ACL while quad muscle is contracting, especially when knee is at 0-30 degrees
- main forces: hyperextension and marked internal rotation
PE
- Lachman and Anterior Drawer Tests
Rad
- MRI determines severity of injury
- hemarthrosis present in 70% of ACL injuries
Tx
- partial tears tx’d conservatively with rest, bracing, and PT
- completely tears tx’d surgically with allograph or autograph reconstruction
PCL Injuries
MOI
PE
Rad
Tx
MOI
- 45% is trauma (i.e.dashboard injuries)
- 40% athletics (esp. soccer)
- hyperflexion is the MC mechanism for isolated PCL injuries
PE
- Posterior drawer test (best)
- Posterior sag sign
MRI used
Tx
- PCL has capacity to heal
- tx conservatively generally–risk of patellofemoral arthrosis
- operative tx in acute injuries, esp. in young, active pts
Baker’s Cyst
Patho
Children vs. Adults
Tx
Patho
- herniation of synovial membrane through joint capsule
- normal fluid flow through a normal communication of a bursae
Children
- Common
- DDx: lipomas, xanthomas, vascular tumors, fibrosarcomas (US to r/o scary stuff)
- most resolve in 10-20 months
Adults
- frequently associated with meniscal tears and chondral injuries
- giant cysts can be found in RA
- rupture can very painful and can resemble DVT
- tx: generally conservative (knee injection, PT which is very effective)
Surgery–very high rate of recurrence
Bursitis
Which bursa MC’ly
MOI
Tx
Bursa involved MC’ly
- prepatellar
- infrapatellar
- pes anserine
MOI
- usually insidious onset and caused by repetitive motions
- if acute think about trauma and INFECTION
- septic bursitis is usually secondary to trauma or cellulitis; LC from septic arthritis or bacteremia
Tx
- if uncomplicated: conservative tx
- -compression, ice, activity modification, sometimes injection
- if infection consider I&D, cultures (refer)
Patellar Fx
MOI
Rad
Tx
Complications
MOI
- Direct trauma: dash board injury or fall directly on it
Rad
- plain films
- some may require CT but usually unnecessary
Tx
- non operative if displaced <3mm, not transverse (avulsion) fx, extension preserved and closed fx
- operative if any of the above criteria are not met
Complications
- if does not healing normally, consider osteochondroitin dissencans (OCD)
- loss of blood supply under the joint surface usually secondary to unrecognized trauma.
- usually in young adults/adolescents
