MSK Joints of the lower limb

Question 1

What type of joint is the ankle joint?

What bones articulate in the ankle joint?

Answer 1

Synovial hinge joint

Tibia, fibula, talus

Question 2

What are the articulating surfaces of the ankle joint?

Answer 2

The tibia and fibula are bound together by strong tibiofibular ligaments. This produces a bracket shaped socket covered in hyaline cartilage - known as a MORTISE

The talus fits into the mortise

Question 3

What are the major ligaments of the ankle joint?

Answer 3

Two sets of ligaments arising from each malleolus

The medial ligament consists of 4 separate ligaments which fan out, attaching to the talus, calcaneus and navicular bones. The medial ligament resists over eversion of the foot

The lateral ligament over inversion of the foot. Formed by 3 separate ligaments:
Anterior talofibula - lateral malleolus to lateral talus
Posterior talofibula - lateral malleolus to posterior talus
Calcaneofibular - lateral malleolus to calcaneus

Question 4

What is an ankle sprain? What structure is most likely to be damaged?

Answer 4

Partial/complete tears of the ankle ligaments - usually occurs in a plantarflexed weight bearing foot which is excessively inverted.

The lateral ligament (particularly the anterior talofibular) is more likely to be damaged because it is weaker than medial and resists inversion

Question 5

What is a Potts fracture and what are the stages involved?

Answer 5

A bimalleolar (both malleoli) or trimalleolar (both malleoli and tibia) fracture. Produced by forced eversion of foot.

1. Forced eversion pulls on medial ligaments causing avulsion fracture of medial malleolus
2. Talus moves laterally and breaks the lateral malleolus
3. Tibia forced anteriorly, shearing off the distal and posterior part against the talus

Question 6

What is the ‘ankle ring’?

Answer 6

The ankle joint and associated ligaments can be visualised as a ring in the coronal plane.

Upper ring is articular surfaces of tib + fib
Lower ring is subtalar joint (talus and calcaneus)
Sides of the ring are medial and lateral ligaments

Likely to be 2 fractures - ring so polo mint

Question 7

What type of joint is the knee joint?

Answer 7

Bicondylar synovial joint - mainly allows for flexion and extension with some degree of medial and lateral rotation

Question 8

What are the articulating surfaces of the knee joint?

Answer 8

Tibiofemoral articulation - medial and lateral condyles of tibia articulating with tibia

Patellofemoral articulation - anterior distal femur articulating with the patella

Both surfaces lined with hyaline cartilage

Question 9

What are the menisci?

Answer 9

Medial and lateral menisci are C shaped fibrocartilage structures that attach to the intercondylar area of the tibia. They serve 2 functions:

• deepen the articular surface of the tibia which increases stabilty of the joint
• shock absorbers

Question 10

Which of the lateral and medial menisci is most likely to be damaged and why?

Answer 10

Medial meniscus because it is fixed the the tibial collateral ligament and the joint capsule so any damage to the ligament will tear the meniscus

Question 11

What are the major bursae in the knee joint?

Answer 11

Suprapatella bursa - between quadriceps femoris and femur. Is an extension of the synovial cavity of the knee

Prepattela bursa - found between apex of patella and skin

Infrapatella bursa - split into deep and superficial. Deep lies between tibia and patella ligament and superficial lies between patella ligament and skin

Semimembranosus bursa - posterior to knee joint, between semimbranosus and gastrocnemius

Question 12

What are the major ligaments of the knee?

Answer 12

1. Patellar ligament: continuation of quadriceps femoris tendon that attaches to tibial tuberosity
2. Collateral ligaments that prevent medial and lateral movement:
   - medial collateral ligament which attaches to medial epicondyle of femur to medial surface of tibia
   - lateral collateral ligament which attaches to lateral epicondyle of femur to lateral surface of fibular head
3. Cruciate ligaments connect the femur and tibia:
   - anterior cruciate ligament, anterior intercondylar region of tibia to intercondylar fossa of femur. Prevents anterior dislocation

• posterior cruciate ligament, posterior intercondylar region of tibia to intercondylar fossa of femur. Prevents posteror dislocation

Question 13

What causes damage to the collateral ligaments of the knee and how do you assess this?

Answer 13

Force applied to side of knee while the foot is on the ground.
Assessed by asking patient to medially and laterally rotate leg - pain of medial = damage to medial ligament and visa versa with lateral

If tibial collateral ligament damaged then medial meniscus is probably torn

Question 14

What causes damage to the cruciate ligaments of the knee and how would you test for damage?

Answer 14

Anterior cruciate damaged by hyperextension or large force to back of the knee while partly flexed.

To test for this use the anterior drawer test - attempt to pull the tibia forwards and if it does the ligament is torn.

Posterior cruciate damaged by ‘dashboard injury’ - large force applied to the skin while the knee is flexed which pushes tibia posteriorly.

To test for this use to posterior drawer test - hold knee in flexion and push shin posteriorly, if there is movement the ligament is torn.

Question 15

What is ‘housemaids knee’?

Answer 15

Friction between skin and patella causes prepatella bursa to become inflamed.

Question 16

What type of joint is the hip joint?

Answer 16

Ball and socket synovial

Question 17

What are the articulating surfaces of the hip joint?

Answer 17

Head of femur and the acetabulum

Both surfaces covered in articular cartilage

Question 18

What are the major ligaments of the hip joint?

Answer 18

Intracapsular:
1. Ligament of head of femur - runs from acetabular fossa to fovea of femur. It encloses a branch of the obturator artery.

Extracapsular:
1. Iliofemoral - runs from ilium to intertrochanteric line in 2 spaces so the ligament is Y shaped. Prevents hyperextension.

2. Pubofemoral - iliopubic eminance and obturator membrane then blends with articular capsule. Prevents excessive extension and abduction
3. Ischiofemoral -ischium to greater trochanter (posterior) Prevents excessive extension.

Question 19

What is the vascular supply to the hip joint?

Answer 19

Medial and lateral circumflex femoral arteries (branches of profunda femoris artery) and the artery to head of femur.

The medial circumflex femoral artery provides majority of blood supply because the lateral has to penetrate the thick iliofemoral ligament. Damage to medial can result in avascular necrosis of head of femur

Question 20

What is the innervation of the hip joint?

Answer 20

Femoral, obturator, superior gluteal and nerve to quadratus femoris

Question 21

What structures increase the stability of the hip joint?

Answer 21

The acetabulum is deep so encompasses almost all the femoral head which decreases risk of dislocation

The acetabular labrum is a fibrocartilaginous collar around the acetabulum which increases its depth

The ilio/pubo/ischiofemoral ligaments are very strong so stabilise the joint greatly. They have a unique spiral orientation which causes them to become tighter when the joint is extended increasing stability

(anteriorly where muscles are weakest ligaments are strongest and visa versa posteriorly)

Question 22

What is the cause of a hip fracture?

What are the consequences?

Answer 22

Name misleading because its actually a fracture to the neck of femur
In 40s the cause is usually a fall, most common in women due to osteoporosis

Affected limb often laterally rotated, arteries from medial circumflex femoral artery usually torn causing avascular necrosis of femoral head and neck

Question 23

What are the 2 types of dislocation of the femoral head?

Answer 23

Congenital dislocation (8x more likely in girls)
Relatively common
During development femoral head not placed in acetabulum resulting in dislocation
- inability to abduct, affected limb shorter, positive trendelenburg sign

Predisposes to arthritis in later life

Acquired dislocation
Relatively uncommon
Usually due to traumatic accidents
2types:

Posterior - more common
Femoral head forced posteriorly, affected limb shorter and medially rotated
Sciatic nerve can be damaged causing paralysis to hamstrings and all muscles distal to knee

Anterior - more rare
Caused by extension abduction and lateral rotation