Will Blakeney- The Knee Flashcards
What are the bones of the knee?
Tibia + femur –> tibiofemoral articulation
Patellar –> patellar-femoral articulation
Fibular is lateral to tibia
What are the ligaments of the knee?
4 Most Important:
- 2x cruciates: anterior and posterial (ACL and PCL
- 2x collaterals: Medial and Lateral (MCL and LCL)
- Medial patellar femoral lig (patellar stability)
- Other ligaments are of lesser important
Muscles of the knee
Extensors:
- Rectus femoris
- Vastus intermedius
- Vastus lateralis
- Vastus medialis
Flexors:
- Semitendinosus
- Biceps femoris
- Semi-membranous
What are the tendons of the knee?
Quadriceps tendon inserts into the patellar tendon
Patellar tendon is inferior to patellar and inserts into tibial tuberosity = extensor mechanism (key for knee extension
ITB
Patellar retinaculum
What are the meniscus?
Increase stability and articular congruency
Distribute load during weight bearing (take 50% of weight bearing in ext, 90% in flex)
Control complex rolling + gliding of the joint as it goes from flex to extension
Medial meniscus, Lateral meniscus
- Medial is more C shaped + larger + less mobile due to greater attachments to capsule (most frequently injured) and Lateral is more spherical
Damage to them can lead to early OA
What should you ask in a knee Hx?
Pain
Swelling (intra-articular or extra-articular)
Stiffness (classic in OA after inactivity like in the morning)
Locking (knee suddenly can’t be fully extended (torn meniscus or loose body between the surfaces)
Deformity
Giving way (ligament injury or possibly capsule, meniscus or muscle weakness)
Limp (due to pain, instability or deformity)
Loss of function (reduced walking distance, inability to run, difficulty going up and down steps)
+ Mechanism of injury if there was a trauma
- Direct blow, to which side, direction of the force
E.g. PCL is commonly a blow to the front of the knee, Blow to the side is more a collateral ligament, twisting injuries are cruciate ligaments or meniscal injury
What are some common gait abnormalities?
Fixed flexion
Hyper-extension
Lateral/medial thrust
What are the 4 groups of special tests for the knee?
- Tests for intra-articular fluid
- The patellofemoral joint
- test for stability (collateral and cruciate ligaments e.g. Lachmann’s)
- Tests for Meniscal injuries (e.g. McMurray’s test)
What is the DDx for Anterior Knee Pain
- Patellofemoral Disorders
- Patellar instability
- Patellofemoral overload
- Osteochondral injury
- Patellofemoral OA - Knee Joint Disorders
- Osteochondritis dissecans
- Loose body in the joint
- Synovial chondromatosis
- Plica syndrome - Periarticular Disorders:
- Patellar tendinitis
- Patellar lig strain
- Bursitis
- Osgood-Schlatter Disease - Referred from the hip
What can cause acute knee swelling?
- Post-traumatic hemarthrosis
- Immediately after joint is this
- ACL, Fracture, Meniscus
- Feels warm + tense, painful, restricted movement, Need X-Ray to rule out # - Bleeding disorders
- Coagulation disorders commonly present with acute knee bleed - Acute septic arthritis
- Ortho emergency requiring prompt Mx (surgical drainage and irrigation, IV ABx)
- Extreme pain on movement, elevated inflamm markers, aspiration reveals pus, high WCC, possible bacteria - Traumatic Synovitis
- Injury to the knee stimulates reactive synovitis - Aseptic non-traumatic Synovitis
- Acute swelling with no trauma or infection sign is this
- Gout, pseudogout, inflammatory arthropathy
- Aspiration: crystals
- mx: anti-inflamms
What is the DDx of chronic knee swelling?
- Intra-articular:
- Arthritis (OA or inflammatory e.g. RA)
- Synovial disorders (synovial chondromatosis, PVNS) - Bony Swelling
- Osteochondroma
- Osgood Schlatter
- Malignancy
What are some causes of anterior knee swelling?
Prepatellar bursitis/Housemate’s Knee
- fluctuant swelling confined to front of patellar
- Doesn’t involve joint itself
- Recurrent friction between skin and bone
- Worker’s on their knees a lot (pavers, carpet layers)
- Mx: bandaging, avoid kneeling, maybe aspiration, may need to excise the lump
Infrapatellar Bursitis
- Similar but involves a bursae inferior or deep to patellar tendon or the pes anserinus
Other Bursae
What are some causes of posteior Knee Swelling
Baker’s cyst
- Bulging of the posterior capsule and synovial herniation
- Swelling in the popliteal fossa
- Usually in the midline
- Presents in older people with OA
- Occasionally ruptures with causes posterior calf pain
Semimembranosus Bursa
- Bursa between medial head of gastrocnemius and semi-menbranosus
- Can become enlarged and is usually a painless lump, slightly medial
- Self-limiting and resolves with time
Popliteal aneurysm
- Pulsation in the lump!!!
- Commonest limp aneurysm
- Thrombosed doesn’t pulse but feels almost solid not fluctuant
Case 1 Diagnosis:
25 yo soccer player
Non-contact pivoting injury
Felt a pop
Immediate knee swelling and pain
Unable to play on
ACL injury
ACL Injury presentation
Most common knee lig injury!!
- often ruptured during sport
- Commonly when suddenly changing direction or landing and twisting from a jump
- ACL limits forward movement of the tibia of the femur + important for rotational stability –> so you get instability
- Rare for it to heal satisfactorily by itself (synovial fluid present around the ligament stops formation of a consolidative clot to promote healing in the ligament)
