The Knee Flashcards
What are the important structures of the tibia?
- Tibial plateau
- Lateral and medial epicondyles of the tibia
- Medial and lateral menisci
- Transverse ligament (between the menisci)
- ACL and PCL insertion
Important ligaments of the Knee
Collaterals
- MCL: prevents excess valgus stress
- LCL: prevents excess varus stress
Cruciates
- ACL: prevents anterior dislocation of knee
- PCL: prefents posterior dislocation of the knee
Popliteal fossa: borders and contents
- Superomedial: semimembranosus
- Superolateral: biceps femoris
- Inferomedial and Inferolateral: medial and lateral heads of gastrcnemus
Contents
- Tibial Nerve
- Popliteal Artery
- Popliteal Vein
Nerves of the knee
Anterior nerves
- Femoral nerve runs down the anterolateral aspect of the knee
- At the level of the knee is becomes the saphenous nerve, which runs down to the foot
- The saphenous nerve branches to give a intrapatellar branch
- These are purely sensory
Posterior nerves
- The obturator nerve runs down the posterior nerve
- In the popliteal fossa, the tibial nerve runs down
- The tibial nerve branches to give the common peroneal nerve, which branches into the:
- Deep peroneal nerve = foot dorsiflexion + sensation
- Superficial peroneal nerve = foot eversion and sensation
Vasculature of the knee
- The femoral artery becomes the popliteal artery at the level of the knee
- Popliteal artery gives rise to anterior tibial artery and posterior tibial artery
- Anterior tibial artery – dorsalis pedis
- Posterior tibial artery – common peroneal artery
Classification of knee replacements
Can be classified based on compartment, stability and cement.
COMPARTMENT
- Unicompartmental: only one part replaced, suitable for younger, highly active patients
- Total knee replacement: both compartments replaced.
STABILITY
- Non-constrained: PCL is used to maintain stability between the femur and tibia, which are separate
- Semi-stable: PCL is not used to maintain stability but there is a central tibial spine which connects it to the femur
- Constrained: hinge mechanism between the tibia and femur with no use of PCL
CEMENT
- Cemented: cement between the bone and the prosthesis
- Uncemented
Baker’s cyst
- Collective of synovial fluid in the popliteal fossa
- Best seen on standing
- Soft and non-tender
- Due to underlying knee pathology where effusion leads to cyst
- Can mimic DVT if ruptured
- Can also cause DVT if it compressed the popliteal vein
What are the different grades of ligamentous injury?
Grade 1 - fibres intact, no instability, changes on MRI
Grade 2 - fibres intact with some instability
Grade 3 - complete tear
Injuries of the collateral ligaments
Presentation
- May have audible pop
- Pain around the joint line
- Effusion
- Reduced ROM
- Locking/clicking/giving way
Investigations
- X-rays: AP and lateral stress views
- MRI
Management
- Conservative: physiotherapy, rest
- Medical: analgesia
- Surgical: repair or reconstruction
Meniscal injuries
- Common in athletes
- Medial meniscus more commonly injured
- Under 50 years = meniscal injury
- Over 50 years = degenerative change
Presentation
- Pain around the joint line
- Swelling
- Effusion
- Positive McMurray’s test
- Painful to deep squat
Investigations
- MRI is gold standard
- Arthroscopy
Management
- Conservative: physiotherapy, rest
- Medical: analgesia
- Surgical: repair or partial meniscectomy
Which nerves should you test for collateral ligament damage?
MCL - saphenous nerve (sensation anterior to medial malleolus)
LCL - common peroneal nerve (foot drop)
ACL injuries
- More common in women
- Leads to haematoma due to rich supply from middle geniculate artery
Presentation
- Audible pop
- Sudden, intense, deep knee pain
- Unable to continue activity
- Rapid swelling and bruising
- Haematoma formation
- Tenderness at lateral femoral condyle and lateral tibial plateau
- Lachmann’s test positive
Investigations
- X-rays: AP and lateral stress views
- May see Segond fracture of the lateral tibial condyle (avulsion fracture)
- MRI
Management
- Sedentary: PRICE, rest, analgesia, PT
- Active: repair or reconstruction can be done around 2 weeks after swelling resolves
PCL injuries
- Less common
Presentation
- Pain in posterior knee
- Posterior sag
- Positive posterior draw test
Investigations
- X-rays: AP and lateral stress views
- MRI: visual if partial or complete tear
Management
- Conservative: PRICE, rest and physiotherapy
- Medical: analgesia
- Surgical: repair or reconstruction can be done in complete tears
Quads tendon rupture
Rupture of the quadriceps tendon, which is involved in knee extension.
Presentation
- There is usually underlying tenindopathy
- Pain at anterosuperior knee
- Unable to extend knee against resistance
- Palpable defect superior to the knee
Investigations
- X-ray: patella baja (low patella)
- MRI
Management
- Conservative: rest, physiotherapy
- Medical: analgesia
- Surgical: tendon repair with reattachment to patella
Patellar ligament rupture
Rupture of the patellar ligament which is involved in knee extension.
Presentation
- Infrapatellar pain
- Haemarthrosis
- Ecchymoses
- Unable to perform straight leg raise
Investigations
- X-ray: patella alta (high patella)
- MRI
Management
- Conservative: rest, physiotherapy
- Medical: analgesia
- Surgical: tendon repair with reattachment
