Week 7 finished Flashcards
Simon is a 34 year old marketing coordinator for an accounting firm. He usually keeps fit by entering several triathlons and fun runs each year; he tells you he would typically average around 30km of running and 40km cycling each week.
Simon has just returned to Melbourne after 14 months working in Beijing where he was so busy with work that the only real exercise he got was the odd game of golf. He decided the only way he would get back into shape was to sign up for a half marathon; he’s training for this when he comes to see you.
Simon presents to you complaining of bilateral shin pain, which began shortly after his return to running. The pain initially came on after a run and he continued to train with the pain, in the hope it would resolve spontaneously. He’s consistently had the pain during and after running for about 4 weeks now and has decided it’s time to seek help.
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- What are the attachments and functions of the two menisci? Which is more commonly injured and why?
Two (med. & lat.) wedge-shaped, fibrocartilaginous discs, are attached to the tibial condyles
FUNCTIONS:
- Serve to increase the curvature of the tibial condyles, increasing joint congruency.
- assists in weight distribution, friction reduction, shock absorption and stability.
Horns and periphery are well innervated with nociceptive and proprioceptive fibres, indicating a role in providing information about joint position and motion and tissue deformation.
ATTACHMENTS:
- Medial meniscus = semi-circle
- Lateral meniscus = 4/5 of a circle
- The open ends are termed horns and are attached to their respective intercondylar tubercles.
- Some fibres of the anterior cruciate ligament (ACL) join the horns.
- The anterior horns are joined by the transverse ligament.
- Coronary ligaments anchor the periphery of each meniscus to the plateau.
- Each meniscus is attached to the patella by capsular thickenings called patellomeniscal ligs.
- The medial meniscus is also attached to the medial collateral ligament and the semimembranosus muscle.
- The lateral meniscus is also attached to the posterior cruciate ligament (PCL) and popliteus muscle.
INJURIES:
Medial compartment of the knee carries vast majority of weight. Twisting force, particularly to a flexed knee may result in meniscal tear. Media meniscus is torn much more frequently due to less mobility (attachment to medial collateral, semimembranosus, ACL and more numerous coronary ligaments) of the meniscus itself but increase ROM and weight bearing of the medial compartment.
- Which parts of the menisci have vascular and neural supply?
Horns and periphery are well innervated with nociceptive and proprioceptive fibres.
Only the outer third of the meniscus is vascularised so often there is little effusion.
- What are plicae and bursae?
Plicae = folds of synovial tissue which occur to various extents in individuals.
Bursae = There are a great number of bursae associated
with the knee complex. These act to reduce friction between the many tendons and ligaments and bony structures.
- The four bursae, which communicate with the synovial cavity:
- Suprapatellar
- Popliteal
- Anserine
- Gastrocnemius.
- What is a popliteal cyst?
Popliteal or Baker’s cysts = fluid filled sacs in the popliteal region and usually result from chronic knee effusion.
The cyst may be a herniation of gastroc or semimem bursa or the synovial membrane.
- Largely painless, they may cause restricted movement and consequent ache in adults.
- Often resolve spontaneously.
NOT TO BE CONFUSED WITH A POPLITEAL ANEURYSM
o Will be painful
o Will be pulsitile and have a bruit.
o Oedema and pain in popliteal fossa
o May stretch tibial nerve referring to medial calf, ankle and foot
- List the four major ligaments of the knee and the motions resisted by each
MEDIAL COLLATERAL LIGAMENT:
Attaches to the medial aspect of the medial femoral condyle and inserts into the medial aspect of the proximal tibia (below the plateau). Blends with the joint capsule and attaches to the medial meniscus.
- Resists valgus stress, especially in the extended knee. (However, it may actually be more significant in the flexed position, when other ligaments are more lax)
- Checks lateral rotation & Taut in extension
LATERAL COLLATERAL LIGAMENT:
Strong cord extending, posteriorly, from the lateral femoral condyle to the head of the fibula
- Resists varus stress
- Resists lateral rotation combined with posterior displacement of the tibia
- Taut in extension
ANTERIOR CRUCIATE LIGAMENT
Attaches to the anterior tibia and extends, posteriorly and superiorly, to attach to the posterior part of the inner aspect of the lateral femoral condyle.
- Resists anterior displacement of the tibia on the femoral condyles.
- Checks both internal and external rotation.
- Medial rotation as ACL is tensed as it winds around the PCL and lateral rotation as it is stretched over the lateral femoral condyle.
POSTERIOR CRUCIATE LIGAMENT
Attaches to the posterior tibia and runs superiorly and anteriorly to attach to the inner aspect of the medial femoral condyle.
- Shorter and less oblique than the ACL
- Resists posterior displacement of the tibia on the femur.
- Resists varus and valgus stress
- Tension in the PCL in extension may be instrumental in creating the external rotation of the tibia, critical to the locking mechanism.
- Limits internal rotation
- Describe the locking mechanism of the knee and its role. What is the action of popliteus?
o Longer medial condyle continues to roll and slide posteriorly (after lateral has stopped), creates involuntary rotation.
- Open kinematic chain: External rotation of tibia
- Close kinematic chain: Internal rotation of femur
o This rotation brings the knee joint into the close-packed position, in which the intercondylar
tubercles are lodged in the intercondylar notch, the menisci are tightly wedged between femoral and tibial condyles and the ligaments are taut.
o This mechanism allows the patient to maintain an erect posture, with an extended knee, for long periods, with little muscular activity
To initiate flexion, this mechanism must be unlocked by internal rotation of the tibia on the femur by the poplitus muscle, or passive knee flexion.
- Why is the knee prone to dysfunction caused by loose bodies in the joint? What conditions predispose to loose bodies?
Because the knee locks in full extension with very little space between joint surfaces, the knee is very
susceptible to pain caused by loose bodies:
o Osteochondritis dessicans (avascular necrosis of joint surface – 1-3 loose bodies)
o Osteochondral fracture
o Osteoarthritis
o Synovial chondromatsis (snow storm knee)
- List the functions of the patella.
- Anatomical pulley
- Increases arm lever of the quads by deflecting the action line away from the axis of the joint.
- Reduces friction between the quads tendon and femoral and tibial condyles.
- Centralises the pull of the quads.
- Define genu valgus and varus. How do these influence patella dislocation?
Genu Valgum: Knock Knees
a medial tibiofemoral angle that is:
- >195 degrees
- or a Q angle of >20 degrees.
It causes increased compressive forces on the lateral condyles and increases tensile force on the medial ligaments. It also creates an increased lateral pull on the patella.
Genu Varum: Bow Legs
A medial tibiofemoral angle that is:
- < 180 degrees.
Rarely measured using Q angle.
Creates increased compressive forces on the medial condyles and tensile stress on the lateral ligaments.
Patella more likely to dislocate laterally, usually due to genu valgum, hence more common in females (females have a greated Q angle)
- List the borders and contents of the popliteal fossa.
- Superior lateral border: Biceps femoris insertion
- Superior medial border: Semimembranosus and semitendinosus
- Inferior lateral border: Lateral head of gastrocs
- Inferior medial border: Medial head of gastrocs
- Roof: Skin and fasica
- Floor: Popliteal surface of the femur, oblique popliteal ligament and the popliteal fascia.
Contents:
- Popliteal vessels (artery, vein, lymph)
- Fat
- Tibial and common peroneal nerves
- Small saphenous vein
- Popliteal lymph nodes
- Popliteal bursa
- End branch of the posterior femoral cutaneous nerve
- Articular branch of the obturator nerve.
- List the muscles and major vessels and nerves present in each compartment of the leg.
POSTERIOR COMPARTMENT:
NERVES:
- Tibial Nerve
ARTERIES:
- Post Tibial Artery & Veins
- Peroneal Artery & Veins
MUSCLES: Superficial layer: - Soleus - Gastrocnemius - Plantaris
Deep layer:
- Popliteus
- Tibialis posterior
- Flexor digitorum longus
- Flexor hallucis longus
LATERAL COMPARTMENT:
NERVES:
- Superficial Peroneal Nerve
ARTERIES:
- Peroneal Artery
MUSCLES:
- Peroneus longus
- Peroneus brevis
- Peroneus tertius
ANTERIOR COMPARTMENT:
NERVES:
- Deep Peroneal Nerve
ARTERIES:
- Ant Tibial Artery & Veins
MUSCLES:
- Tibialis anterior
- Extensor hallucis longus
- Extensor digitorum longus.
- Where can each component of the peroneal nerve be compressed or injured?
Common peroneal nerve:
o Superficial and therefore most commonly injured
o Supplies mm in lateral and anterior compartments = foot drop
o Severed or stretched in fractures of fib head or by direct trauma to the side of the knee/fib head.
Superficial peroneal nerve:
o Stretch in ankle sprains (causing pain, paraesthesia and numbness in the lateral leg and dorsum of the foot)
Deep fibular nerve:
o Entrapment may follow overuse or injury of the
anterior compartment resulting in anterior compartment pain extending to the dorsum of the foot and between 1st and 2nd toes.
o Tight fitting ski boots often compress this nerve under the extensor retinaculum, causing pain and numbness in the dorsum of the foot and between the 1st and 2nd toes.
- List the superficial veins of the lower extremity and give a brief description of their location.
GREAT SAPHENOUS VEIN:
Originates from where the dorsal vein of the big toe (the Hallux) merges with the dorsal venous arch of the foot. It passes anterior to the medial malleolus. Ascends on the medial aspect of the leg and at the knee, it runs over the posterior border of the medial epicondyle of the femur bone.
Then courses anteriorly to lie on the anterior surface of the thigh before entering an opening in the fascia lata called the saphenous opening. It forms an arch, the saphenous arch dives into the femoral triangle to drain into the femoral vein.
SMALL SAPHENOUS VEIN:
Begins where the dorsal vein from the fifth digit (smallest toe) merges with the dorsal venous arch of the foot.
From its origin, it courses around the lateral aspect of the foot (inferior and posterior to the lateral malleolus) and runs along the posterior aspect of the leg (with the sural nerve), where it passes between the heads of the gastrocnemius muscle.
Usually it drains into the popliteal vein, at or above the level of the knee joint.
Clinical application
Simon decided to seek treatment because the shin pain has become obvious when walking and after even a light jog the pain is lingers for some time and may continue into the night. He also tells you that his first few steps in the morning are excruciating.
On examination, you note medial shin tenderness, particularly distally. Both feet are relatively pronated. Active resisted inversion and plantar-flexion reproduces his pain.
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