Trauma and orthopaedics (2): The knee Flashcards
Bony surfaces of the knee joint
- Condyles of femur
- Condyles of the tibia
- Patellar surface of femur
- Articular surface of patella
the distal femur anatomy
do a purpose games
intercondylar area
Provides attachments for the cruciate ligaments and the lateral and medial meniscus
femoral condyles vs epicondyles
Epicondyles originate above the condyles
- medial larger of two
- medial and lateral collaterals originate from respective epicondyles
Condyles
- Medial is larger than later-takes more weight
how the knee joint all comes together
Distal femur (trochlea)
Anteriorly- shallow depression for articulation with patella
- Trochlea or patellofemoral groove
- Lateral lip of trochlear groove is more prominent- resist patellar dislocation
Posteriorly- deep notch
- Intercondylar fossa
Proximal tibia
- Intercondylar eminence fits into intercondylar fossa
the patella
- Largest sesamoid bone
- Its superior aspect is attached to the quadriceps tendon, and its inferior aspect to the patellar ligament
The posterior surface of the patella articulates with the femur, and is marked by two facets:
- Medial facet: articulates with the medial condyle of the femur.
- Lateral facet: articulates with the lateral condyle of the femur.
main functions of the patella
- By enabling the quadriceps muscle to directly cross the anterior aspect of the knee and by acting as a fulcrum, the patella enhances the leverage that the quadriceps tendon can exert on the femur, increasing the mechanical efficiency of the muscle by 33-50%.
- Protection. It protects the anterior aspect of the knee joint from physical trauma.
- It reduces the frictional forces between the quadriceps and the femoral condyles during extension of the leg
the tibia
- Main bone forming the leg (shinbone)
- Expansion at proximal (medial and lateral condyles) and distal ends where it articulates at the knee and ankle
- Second largest bone in the body- weight bearing structure
Tibial plateau
Condyles form a flat surface called the tibial plateau
- Articulates with the femoral condyles
- Head of the fibula articulates with the proximal tibia at the proximal tibiofibular joint (not forming part of the knee joint)
tibial shaft has 3 borders
-
Anterior border
- Marked by the tibial tuberosity
- Insertion site for the patellar ligament
-
Posterior border
- Marked by a ridge of bone known as soleal line
- Site of origin for part of the soleus muscle
-
Lateral border
- Interosseous border
- Site of attachment for the interosseous membrane that binds the tibia and fibula together
distal tibia
- Widened due to medial and lateral malleolus → assists with weight bearing
- Articulates with tarsal bones to form part of the ankle joint
- Laterally, there is the fibular notch, where the fibula is bound to the tibia, forming the inferior tibiofibular joint.
fibula
- Located in the lateral aspect of the leg
- Attachment site for muscles rather than bearing weight
3 major articulation of fibula
- Proximal tibiofibular joint- articulates with the lateral condyle of the tibia
- Distal tibiofibular joint- articulates with the fibular notch of the tibia
- Ankle joint- articulates with the talus bone of the foot
proximal fibula
At the proximal end, the fibula has an enlarged head, which contains a facet for articulation with the lateral condyle of the tibia.
The common peroneal (common fibular) nerve winds around the posterior and lateral surface of the neck of the fibula, so is vulnerable to damage in a proximal fibular fracture.
distal fibula
Lateral surface continues inferiorly to the lateral malleolus
- The lateral malleolus of the fibula is more prominent than the medial malleolus of the tibia and can be palpated at the ankle on the lateral side of the leg
articulating surfaces of the knee
-
Tibiofemoral- medial and lateral condyles of the femur articulate with the medial and lateral tibial condyles
- Weight bearing joint
-
Patellofemoral- the patella articulates with the femur at the trochlear (patellofemoral) groove
- Both joints lined with hyalineà single joint cavity
Factors which stabilise the knee joint
- Menisci
- Capsule
- Ligaments
- Muscles
Menisci
The medial and lateral menisci (figure 4.13) are fibrocartilaginous structures in the knee that serve two functions:
- To deepen the articular surface of the tibia, increasing the stability of the joint.
- To act as shock absorbers by increasing surface area to further dissipate forces.
Menisci and collateral ligaments
In addition to the intercondylar attachments medially, the medial meniscus is attached peripherally to the medial (tibial) collateral ligament and the joint capsule. Damage to the medial collateral ligament therefore often results in a medial meniscal tear
ligaments involved in knee joint
- Intracapsular = cruciate ligaments
- Ligaments that strengthen the capsule= oblique popliteal ligament
- Extra-capsular= collateral ligaments
joint capsule
- The joint capsule surrounds the sides and posterior aspect of the knee joint but is deficient anteriorly
- allows the synovial membrane to extend up beneath the patella, forming the suprapatellar bursa
- The capsule is strengthened laterally and medially by the inferior fibres of the vastus lateralis and medialis muscles respectively.
- Strengthened posteriorly by the oblique popliteal ligament
- Expansion of semimembranosus
cruciate ligaments
PAM APpLes! (think proximally from the tibia to the femur)
-
Anterior cruciate ligament (ACL)
- Anterior passes Posterior insets Laterally
-
Posterior cruciate ligament (PCL)
- Posterior passes Anterior inserts Medially
ACL- weaker of the two
- Relatively poor blood supply
- Limits anterior movement of Tibia on Femur
PCL- stronger of the two
- Limits posterior movement of tibia on femur
- In weight bearing flexed knee- PCL is the main stabilizer
Extracapsular ligaments
The medial and lateral collateral ligaments are strap-like ligaments. They act to stabilise the hinge motion of the knee, preventing excessive medial or lateral angulation of the tibia on the femur.
Medial (tibial) collateral ligament
- Wide flat ligament
- Medial side of the joint
- Proximally attached to the medial epicondyle of the femur
- Distally attaches to the medial condyle of the tibia
- Adherent to medial meniscus
- MCL resists valgus (lateral) angulation
- E.g. side tackle
Lateral collateral ligament
Lateral collateral ligament
- Lateral femoral epicondyle to lateral surface of fibular head
- Reinforced by iliotibial tract
- Resists varus force on the tibia (varus= medial)
bursae
A bursa is a small sac lined by synovial membrane, containing a thin layer of synovial fluid.
Function
- cushion between the bones and tendons/muscles surrounding a joint.
- This helps to reduce friction between the bones and soft tissues and allows free movement.
six bursae
- Suprapatellar bursa – This is an extension of the synovial cavity of the knee, located between the quadriceps femoris muscle and the femur.
- Prepatellar bursa – Found between the anterior surface of the patella and the skin.
- Superficial (or subcutaneous) infrapatellar bursa - Between the patellar ligament and the skin.
- Deep infrapatellar bursa - Between the tibia and the patellar ligament.
- Semimembranosus bursa – Posterior to the knee joint, between the semimembranosus muscle and the medial head of the gastrocnemius.
- Subsartorial (pes anserinus) bursa – Between the common insertion of the pes anserinus tendons (sartorius, gracilis, semitendinosus) and the medial tibial condyle
muscles of the anterior leg
- tibialis anterior
- extensor digitorum longus (EDL)
- extensor hallucis longus (EHL)
- fibularis tertius.
The deep peroneal nerve innervates all muscles and is perfused by the anterior tibial artery.
muscles of the posterior leg
do a purpose games
areas of the leg
popliteal fossa
popliteal fossa
Diamond shaped area located on the posterior aspect of the knee- main path by which vessels and nerves pass between the thigh and the leg
borders of the popliteal fossa
Borders
4 borders:
- Superomedial border- semimembranosus
- Superolateral border- biceps femoris
- Inferomedial border- medial head of the gastrocnemius
- Inferolateral border- lateral head of the gastrocnemius and plantaris
- Floor: posterior surface of the knee joint capsule and posterior surface of the femur
- Roof: two layers: popliteal fascia (continuous with fascia lata) and skin
contents of the popliteal fossa
Contents
Main conduit for neurovascular structures entering and leaving the leg. Contents medial to lateral:
- Popliteal artery (deepest structure- continuation of the femoral artery )
- Popliteal vein (small saphenous vein drains into here)
- Tibial nerve
- Common fibular nerve (common peroneal nerve)
Tibial and common fibular nerve
- most superficial and branches of the sciatic nerve.
- The common fibular nerve follows the biceps femoris tendon, travelling along the lateral margin of the popliteal fossa
most commonly affected OA joint
knee
RF for OA
- age
- female
- obesity
- trauma
presentation of knee OA
- pain around knee which can radiate to thigh and hip
- exacerbated by exercise and relieved by rest
- often bilateral
- joint stiffness
- crepitus can be heard
investigations for knee OA
x-ray (AP and lateral_
LOSS
classification of knee OA
Kellgren and Lawrence system
- Grade 0 – no radiographic features of OA are present
- Grade 1 – unclear joint space narrowing and possible osteophytic lipping
- Grade 2 – definite osteophytes and possible joint space narrowing on AP weight-bearing views
- Grade 3 – multiple osteophytes, definite joint space narrowing, evidence of sclerosis, and possible bony deformity
- Grade 4 – large osteophytes, marked joint space narrowing, severe sclerosis, and definite bony deformity
management of knee OA
conservative
- weight loss
- regular exercise
- smoking cessation
- analgesia (WHO analgesic ladder)
- physiotherapy
surgical
- total knee repalcement (function for at least 10 years)
- partial knee replacement (unicondylar) if localised
tibial plateau fracture cause
- high energy trauma causing impaction of femoral condyle onto the tibial plateau
- can be in elderly with osteoporosis
what sort of force causes tibial plateau fracture
varus-deforming force, meaning that the lateral tibial plateau is more frequently fractured than the medial side.
They are often found alongside other bony and soft tissue injuries, such as meniscal tears or cruciate or collateral ligament injury.
presentation of tibial plateau fracture
- trauma via high impact injury
- sudden onset unable to weight-bear
- swelling
- check neurovascular status
investigations for tibial plateau fracture
X-ray (AP and lateral)
- lipohaemarthrosis present
CT scan eneded in all cases (apart from undisplaced fractures)
what does presence of fat in a joint indicate- lipohaemarthrosis
there is an intra-articular fracture present (e.g. tibial plateau, patella, distal femur)
classification of tibial plateau fracture
Schatzker Classification
conservative management of tibial plateau fracture
can be trialled in uncomplicated tibial plateau fractures (including no evidence of ligamentous damage, tibial subluxation, or articular step <2mm)
These can typically be treated with a hinged knee brace and non- or partial-weight bearing for around 8-12 weeks, alongside ongoing physiotherapy and suitable analgesia.
surgical management of tibial plateau fracture
- Open reduction and internal fixation (ORIF)
- post opp- hinge knee brace (no weight bearing for 8-12 weeks)
if signif soft tissue injury, polytraua and highly comminuted and ORIF not suitible →External fixation with delayed definitive surgery
complication of tibial plateau fracture
post-traumatic osteoarthritis to the affected joint.
