Session 9 - The Knee joint Flashcards
What are the articulations in the knee joint?
- Tibial plateau
- Condyles of femur
- Patella
Which condyle of the femur is larger and why?
- Medial
- Takes more weight
Why is there an anterior shallow depression on the distal femur?
-Where patella articulates
Where is the intercondylar fossa?
-Posterior deep notch of the femur between the condyles
Which epicondyle of the femur has the adductor tubercle?
-Medial
What ligaments attach to the epicondyles of the femur?
-Collateral ligaments
What do the condyles of the tibia form? Describe the surface of this
- Tibial plateau
- Medial surface slightly concave superiorly
- Lateral surface slightly convex superiorly
- Raised and rough areas known as the intercondylar eminence separate the two sides
What bony landmark lies within the tibial plateau?
-Intercondylar eminence
What attaches to the intercondylar eminence?
-Cruciate ligaments
What are menisci?
-Wedge-shaped circular fibrocartilaginous bands which cover the articular surface of the tibia
What is the function of menisci?
- Deepen the articular surface of tibial element
- Provide stabilisation and support
- Act as shock absorbers
How many menisci are there?
-2 (one medial one lateral)
How are the menisci attached at the knee?
- Attached to the intercondylar eminence and to the joint capsule via coronary ligaments
- Attached to each other anteriorly by the transverse ligament of the knee
What factors stabilise the knee joint?
- Menisci
- Muscles (Quadriceps femoris/iliotibial tract)
- Ligaments
What are the intracapsular ligaments which stabilise the knee?
-Anterior and posterior cruciate ligaments
Where does the anterior cruciate ligament attach?
-Anterior tibia, posterior femur
-What is the function of the anterior cruciate ligament?
- Prevents tibia moving anteriorly/femur moving posteriorly
- Limits hyperextension
Which is the weaker cruciate ligament?
-Anterior
Where is the posterior cruciate ligament attached?
-Posterior tibia
What is the function of the posterior cruciate ligaments?
- Stops tibia moving posteriorly, femur moving anteriorly
- Limits hyperflexion
What is a pneumonic to remember cruciate ligaments?
-PAMs APLles
Posterior moves Anteriorly and inserts Medially
Anterior moves Posteriorly and inserts Laterally
What are the main extracapsular ligaments of the knee?
-Medial and lateral collateral ligaments
Where does the medial collateral ligament inserts and attach?
- Extends from medial epicondyle of femur
- Inserts into medial condyle of tibia
- Attaches to medial meniscus
Which collateral ligament blends with the joint capsule and which is separate?
- Lateral is separate
- Medial blends
Where does the lateral collateral ligament attach?
-Lateral fibular head
Except cruciates and collaterals, what other ligaments are involved in the knee joint?
- Patella ligament
- Oblique and Arcuate popliteal ligaments
What is the function of the popliteal ligaments?
-Re-enforce joint laterally
Which muscles extend the knee joint?
-Quadriceps femoris
Which muscles flex the knee joint?
- Sartorius
- Gracilis
- Hamstrings
- Gastronemius
- Plantaris
What muscles internally/medially rotate the knee?
- Semitendinosus
- Sartorius
- Gracilis
- Semimembranosus
Which muscles externally rotate the knee?
-Biceps femoris
Which muscles make the hamstrings?
- Biceps femoris (long head and short head)
- Semimembranosus
- Semitendinosus
- Part of adductor magnus
Where do the hamstrings attach at the pelvis?
-Ischial tuberosity
What nerve innervates the hamstrings?
-Tibial (except short head biceps femoris-> common fibular)
When is the posterior cruciate ligament most often damaged?
-Falling on tibial tuberosity with flexed knee
How is the posterior cruciate ligament tested?
-Posterior draw test
When is the anterior cruciate ligament most commonly damaged?
-during hyperextension
How is the anterior cruciate ligament tested?
-Anterior draw test
Why is the lateral menisci usually undamaged?
-It is mobile
Why do menisci usually heal well?
-They have a good blood supply
What is the unhappy triad?
-Damage to medial collateral ligament, medial meniscus and anterior cruciate ligament
Why is the medial meniscus usually damaged in medial collateral ligament damage?
-They are firmly attached together
When does the unhappy triad usually occur in knee injuries?
- Lateral twisting of flexed knee
- Blow to the side of the knee
What type of arthritis is most common in the knee?
-Osteoarthritis
Which bursa are the most commonly effected by bursitis in the knee?
- Supra-patella
- Pre-patella
- Superficial infra-patella
What is the laymans term for pre-patella bursitis?
-Housemaids knee
What is the laymans term for infra-patella bursitis?
-Clergyman’s knee
What is a popliteal cyst?
-Abnormal fluid filled sacks of synovial membrane in the popliteal fossa
What is a differential diagnosis of popliteal cyst?
-Popliteal artery aneurysm
How are knee injuries most commonly investigated?
- Plain film x-ray
- MRI
- Clinical examination
- Aspiration
- Arthroscopy
Why does the knee joint require extra things for stabilisation?
-The tibial plateau and the condyles of the femur are a mismatch of shapes
Why is the lateral menisci more mobile than the medial?
-Its points of attachment at the eminence are closer to each other allowing for mor movement
What are the most important muscles of quadriceps femoris in stabilising the knee?
- Vastus lateralis
- Vastus medialis
What re-enforces the ligaments of the lateral knee?
-Ilio-tibial tract
The oblique popliteal ligament is an extension of…
…tendon of semimembranosis
Why and how does the knee lock during extension?
- Makes it easier to stand
- Femur rotates slightly internally over tibia and the knee joint can be held in position
What muscle helps to ‘unlock’ the femur?
-Popliteus helps to rotate the femur externally
With what injuries are the menisci usually damaged?
-Medial collateral or anterior cruciate ligament injury
What is the most common cause of bursitis?
- Chronic friction
- Direct trauma
Which bones are involved in the knee joint?
- Femur
- Tibia
- Patella
Describe the blood supply to the knee
- complex genicular anastamoses around the knee
- popliteal artery runs through popliteal fossa
