Clinical anatomy

Question 1

Beryl is a keen cyclist. Recently she has been suffering from pain in her knee, and is noticing it more and more - especially when she’s going down the stairs.

1. What movement is causing her knee pain?
2. What is the underlying cause of beryl’s condition?

Answer 1

1. her patella is rubbing against her lateral femoral condyle
2. it is brought about by her patella not tracking properly

Question 2

What causes the patella to be pulled laterally and therefore not track normally?

Answer 2

• the angle of the femur from pelvis to knee is oblique (slightly inwards)
• whereas the line of pull of the quadriceps muscle is straight
• therefore 2 forces occur - one that extends the knee and one that pulls the patella laterally

Question 3

What 2 factors ensure normal tracking of the patella?

Answer 3

1. raised lateral femoral condyle
2. horizontal fibres of vastus medialis pull the patella medially during knee extension

Question 4

What anatomical features cause women to be more prone to anterior knee pain than men?

Answer 4

• the shape of the female pelvis is wider
• which makes the angle of the femur more oblique (points further inwards)

Question 5

The femoral nerve supplies the anterior thigh compartment, which are mainly responsible for knee extension.

What reflex is the femoral nerve associated with?

Answer 5

The knee jerk reflex

Question 6

The extensor retinaculum holds the long tendons of the anterior leg muscles against the underlying bones as they cross the ankle joint. It also helps redirect the direction the muscles pull in, maximising their efficiency.

What would a fault in the extensor retinaculum cause?

Answer 6

the tendons could lift away from the bones, resulting in ‘bowstringing’

Question 7

Darren presents to A&E after receiving a tackle in a football match. X-ray reveals that he has a displaced tibial fracture. Darren is giving 20mg of morphine, but complains that the pain in his leg has gotten worse. Upon examination, the leg is in a splint and slightly swollen. The dorsalis pedis and posterior tibial pulses are palpable and sensation is normal. On gentle passive movement of Darren’s toes and ankle he is in agony.

A plastic surgeon is called and Darren is sent for an emergency fasciotomy

What is compartment syndrome?

Answer 7

• there is increased pressure within a particular muscle compartment, due to an increase in fluid (eg. blood)
• the pressure increase exceeds the pressure within the capillaries
• this means that they cannot fill and supply blood to structures within that compartment

Question 8

What would have happened if Darren didn’t receive emergency surgery to open the fascia?

Answer 8

avascular necrosis

Question 9

Why were Darren’s dorsalis pedis and posterior tibial pulses still palpable?

Answer 9

• although the pressure is higher than the pressure in the capillaries, the arterial pressure is still higher at this point

Question 10

Following his fracture, Darren is placed in a below-the-knee cast. When the cast is removed, the bone has healed well. However, Darren is concerned by an inability to lift his foot when walking.

Anatomically, what is this action known as?

Answer 10

Ankle extension/dorsiflexion

Question 11

Which muscle compartment is responsible for ankle extension?

Which nerve supplies this compartment?

Answer 11

the anterior compartment of the leg

the deep peroneal nerve

Question 12

The register suggests that the deep peroneal nerve may have been compressed by the cast, leading to Darren’s inability to extend his ankle. Where is the nerve likely to be compressed?

Answer 12

• Around the neck of the fibula
• because the deep peroneal nerve lies deep to the muscles in the anterior leg, so it is unlikely that the nerve has been directly compressed
• however, the deep peroneal nerve is a branch of the common fibular nerve, which enters the leg by wrapping around the neck of fibula (making it very exposed)