Swelling left side of buttock- 6 months' duration. Sagittal T1, Sagittal PD, Axial T1 and Axial T2 fat sat.

There is a loculated fluid collection with septation, and multiple fluid levels (see axial T2 fat sat image). It's adjacent to the left ischial tuberosity. There's a thick rim around the lesion.


Ischial bursitis: also called weaver's bottom

Let's play Name That Structure!

Write in with your answers!

Have a look at the images below. Shoulder pain.

So- still think it's calcific tendinitis?


The patient suffered an anterior dislocation previously. See the defect on the inferior glenoid rim on the radiograph above? That's a bony Bankart.


And if you go up to the fragment shown above, it does look suspiciously like a piece from the glenoid defect. It's too well-circumscribed and well demarcated. Also, with such a large calcific fragment, shouldn't there be more swelling of the tendon?


So, knowing what you now know, it's likely the bone fragment from the bony Bankart displaced up into the supraspinatus tendon! Take home message: if it's too sharp, look again. Calcific tendinosis is fluffy.

OK- so the female patient's breast MRI reveals something quite interesting. Previous ultrasound done at St Elsewhere revealed no focal mass. Agree?

Well, let's go back to the ultrasound images. If you compare the right breast with the left, you'll find that there's asymmetry in the images. There's a hypoechoic focus in the left breast, with thin linear septation. Of course, on MRI you see that there is an intermuscular lipomatous lesion, with some intramuscular components. And you remember that in the breast, fat is hypoechoic- as opposed to other body parts where fat is hyperechoic.


So, sometimes if it's too big you can walk past it. God gave us duplicate body parts to compare.

OK- not a musculoskeletal case. But a nice one anyway. Sagittal T1W, axial diffusion, axial T2W, axial FLAIR and axial T1W.

Epidermoid cyst. Extra-axial. 1% of intracranial lesions. Rarely rupture compared with dermoid cysts (which cause chemical meningitis). Likely congenital- and grow very slowly. 


Read about it here.

As you can see, the images were taken with the knee in semiflexion. We usually acquire them in extension. Bad scan?

So- it's not a bad scan. Pixellated - but that's poor photoshopping.
There's a bucket handle medial meniscus tear (thanks, Dr TS!) with displaced fragment within the intercondylar notch. It's getting in the way of full extension. A classic case of locking.


You see the remnant anterior and posterior horns of medial meniscus, with loss of free edge. The remnants are small- and that's your first clue that it's torn. Scroll slowly, and you see the flipped fragment in the intercondylar notch (look at axial image). The bucket handle is easy to miss because it can blend with the cortex of the intercondylar notch, so be careful. And don't dismiss it as a bad scan.

Coronal and axial T2 fat sat images of the lower limbs. This, taken from a guy who ran a marathon without adequate training.


The images reveal oedema in the gastrocnemius muscles bilaterally, with fluid in the gastrocsoleus myotendinous junction. This is a grade 2/3 myotendinous junction tear. You can see this in tennis players, but bilateral changes are somewhat less common.


Grading of myotendinous junction injuries is as follows:
Grade 1- oedema, without disruption.
Grade 2- partial tear of the myotendinous junction with oedema/haemorrhage
Grade 3- complete tear with oedema and haemorrhage

Image on left is a coronal PD through the midfoot, and fat saturated PD on the right. What do you see?

There's thickening of the Lisfranc ligament (the ligament connecting the medial cuneiform with the base of the 2nd metatarsal bone). There's no joint widening, and no fracture- and would be radiographically occult.


In civil society, this injury can be sustained during football injuries (or kicking someone's tires). In Napoleon's day, you would have a carriage roll over your foot, causing a fracture. Jacques Lisfranc, after whom the injury is named, is taught to treat this injury with a mid-forefoot amputation.


Ligament injuries can be classified as sprains or tears (in which case, there's discontinuity of the ligament). Clinically, there's localised tenderness and pain when squeezing the midfoot.


The injury is well demonstrated on a PD nonfat sat image- so look carefully.  

A few interesting images demonstrating the power of diagnostic musculoskeletal ultrasound.

A subdeltoid bursal effusion. Notice the loss of contact at the proximal part of the probe? It's because we are rounding the lateral part of the shoulder. This is a reminder that subdeltoid effusions can move, and can be located very laterally rather than at the level of the tear. So, you need to go all around the shoulder to look for fluid.

This is biceps tendon is not really normal. While there's no anechoic fluid collection in the tendon sheath, there's echogenicity surrounding the tendon. This is what chronic tenosynovitis looks like- not to be dismissed as normal.

An important plane of scanning to detect tendon tears. In this case, you see a defect in the anterior aspect of the tendon (the ovoid biceps tendon is well demonstrated). There are punctate echogenicities indicative of debris within a subacromial bursal effusion that has filled the tear gap. You can see the cartilage of underlying humerus. 

Another view with the relevant structures highlighted:
Ovoid- transverse view of long head of biceps tendon
Lines- cartilage interface

This is an example of the many causes of "atypical sciatica". Sciatica occurs when the L4, L5, or S1 nerve roots are impinged on their way to the lower limbs. The typical sciatica starts in the lower lumbar spine, and results in shooting pain down the back of the leg.

Atypical sciatica does not start in the spine. Among its many causes includes piriformis syndrome, presacral masses impinging on the sacral plexus, sacral fractures, pelvic masses, gluteal problems (including haematomas and masses), and pelvic fractures.

In this case, it's not easy to see on static images, but you have a varix next to the small sciatic nerve in the back of the lower thigh, at its bifurcation into the tibio-peroneal trunks. The varix herniates into the nerve fascicles, which are then wrapped around it. The sciatic nerve has increased signal relative to the vessel (it should be hypointense to vessels on fat saturated images), and is therefore suspected have neuropathy. There was also asymmetrical muscle hyperintensity on STIR images (not shown).