 This is the lateral compartment of the leg, it is bounded by the posterior intramuscular septum which is attached to the posterior border of the fibula here, remnant of that is visible here and the anterior intramuscular septum which is attached to the anterior border of the fibula, so only this portion is the lateral compartment and we can see a little bit of the intramuscular septum. The muscles of the lateral compartment, this is the fibularis longus, it takes origin from the upper lateral part of the fibula, it is a longer one and under that we can see yet one more muscle, this is the fibularis brevis, which takes origin from the fibula but below. The fibularis longus tendon winds behind the lateral malunus and here it was covered by the fibular retinoculum and we can see remnant of the fibular retinoculum here which held the tendon in place and here it was covered by the cerebellum which has been removed and if you notice very carefully it goes under the sole of the foot and the instrument has disappeared there. From here it goes all the way from the lateral to the medial acetate or the sole of the foot in layer number 4 and it gets attached to the medial cuneiform and the first metatarsal. So from the course of this tendon you can make out that when this contracts it produces aversion of the foot, so this is a very powerful aversion of the foot and it also helps to maintain the transverse arch of the foot. Now let's take the course of the fibularis brevis tendon, this is the one which is under the fibularis longus, this also runs behind the lateral malunus and it is also bridged over by the fibular retinoculum and it is held in place by a facial septum and we can see that facial septum here so that it does not dislocate, however in case of degenerative tendonitis they may dislocate. The tendon then goes forward, this is the course of the fibularis brevis tendon, this is the one which I picked up here and the fibularis brevis then gets inserted onto the tuberosity of the fifth metatarsal bone and we can see the tuberosity here. So this is also an averture, when it contracts it produces aversion of the foot. There is a very important clinical correlation at this juncture here, if the foot is already under aversion by contraction of the fibularis brevis and at that moment if the foot is inverted forcibly then it can produce a version fracture of the tuberosity of the fifth metatarsal and that is known as Dancel's fracture. Now let's take a look at the neuro vascular structures of the lateral compartment. The lateral compartment has its own nerve but it does not have its own artery so it gets arterial supply from the posterior compartment and we shall see that just now. So for that I am retracting the muscles. Let's take a look at the artery here. This artery which I picked up here, this is the circumflex fibular artery. This is a branch from the posterior tibial artery which is in the posterior compartment and it winds around the neck of the fibula. So this is the one which supplies the lateral compartment, it also gets contribution from the anterior compartment. So it does not have its own arterial supply. However, let's take a look at the nerve. I have picked up the common fibular nerve in the paparital fossa. This is the division of the tritone nerve into tibial and common fibular and we can see the common fibular nerve is descending down. Please follow the course of the common fibular nerve with me. It goes behind the head of the fibula then it winds around the neck of the fibula and this is the region where it is liable to be injured in fracture of the neck of the fibula. And from there it goes inside the lateral compartment and we can see it dipping inside. It is supplying the muscles of the lateral compartment and here it is accompanied by the circumflex fibular artery. We can see that also. Let us take a look at the two principal divisions of this common fibular nerve. One is this one which I have picked up and the other is this one which I have picked up. So both the branches are here in front of my instrument. This is the superficial fibular division which supplies the muscle of the lateral compartment namely the fibular strongest and the fibularis brevis. Therefore it disappears here and after it supplies now I am going to pull from here and we can see it is coming here. After it is supplied these muscles it pierces the deep fascia at this level and this is the place in the lower one-third of the leg it becomes subcutaneous and then it runs under the skin. It supplies the skin of the anterolateral aspect of the lower one-third of the leg and then it comes to the foot. Dorsum of the foot is superficial to the extensor retinal level and it supplies the skin of the major part of the dorsum of the foot except the first inter metatarsal space. So this is the course of the superficial fibular nerve. Now let us take a look at the next branch. This is the branch here. Now I have picked up the other division of the common fibular nerve and when I give traction here you will find that this nerve is moving. So this is the deep fibular nerve and we can see the other end of the deep fibular nerve here. We can see it moving. The deep fibular nerve comes to the anterior compartment and then it supplies the muscles of the anterior compartment. The deep fibular and the superficial fibular are rarely injured because they are deep inside the muscle. So the injury most commonly occurs to the common fibular either around the head of the fibular or the neck of the fibular. If the superficial fibular nerve is injured then it will produce paralysis of the fibularis compartment longest and previous. If the deep fibular nerve is injured it will paralyze the muscles of the anterior compartment and lead to foot drop. Superficial fibular nerve can undergo what is known as traction neuropathy in people who suffer from repeated inversion injuries. And in thin people this superficial fibular nerve as it crosses the ankle joint it can be seen as fine fiber standing up under the skin in very thin individuals. And this can be a potential site for giving nerve block of superficial fibular nerve. So this is the course and distribution of the superficial fibular nerve and the deep fibular nerve coming from the common fibular nerve. Thank you very much for watching. Dr. Sanjay Sanyal signing out. If you have any questions or comments please put them in the comment section below. Have a nice day.