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Author Topic: Seeking Help With Patellar Ligament Anatomy (MRI)  (Read 628 times)

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Offline haleba

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Seeking Help With Patellar Ligament Anatomy (MRI)
« on: July 09, 2018, 06:02:54 AM »
I understand the limitations of this forum, but given the long train of MRI questions here I hope at least one member could answer a simple anatomy question.

Background:

Three months ago I was performing 10 repetitions of a single-legged incline press exercise with my right leg when I felt an intense level 6 "tearing" sensation at repetition 5 that felt as if my right patellar ligament was about to break, running through the ligament, patella and into the quadriceps tendon.

The next day I felt a single flash of pain through the ligament while resting, as if a razor blade was slicing it down the middle.

The day after this flash of pain I was asked to do 10 minutes on an elliptical bike. Halfway through I once again felt the start of a tearing sensation running through the ligament and bone, with a sharp "biting" pain at the tendon that forced me to stop and rest before continuing at a much slower pace.

From those two incidents onward, I experienced "stretched" "sandy" level 2 to very occasional nearly level 3 pain in the ligament--especially climbing stairs--that concerned me for quite a while because it often felt as if the ligament was headed toward snapping, along with occasionally prolonged episodes of itching and stinging in the quadriceps tendon, as well as a couple of incidents of a "loose rubber band" sensation in the ligament.

After a drawn out plea for attention I finally got an MRI referral.

When the results came back I was completely dumbfounded by the reading of a complex meniscus tear but with "intact" ligaments and extensor mechanism, even though I wasn't suffering any of the major listed symptoms of meniscal tears, which I learned wasn't that uncommon.

After puzzling over this I finally decided to get my MRI files and when I looked at first (based on my research until then) the simple "intact" finding seemed unassailable, but something still didn't seem right.

It's surprisingly hard to find normal knee images, but in the few I did find the patellar ligament was substantially straight and quite black while mine seemed to have a slightly "limp" curve. From one source:

"The tendons of the quadriceps [as well] as the patellar tendon are homogeneous in signal but don't have to be black on PD-images."

I'm showing a couple of PD images here, but the source goes on,

"They have a sharp posterior demarcation."

and in all the sagittal images, T1 and PD, as well as the axial images, the back of the tendon seems "blurry" (even by the blurry standards of the T1 images) except near the point where it joins the tibia; but above all, in all of the normal MRIs I could find the ligament consistently "nails" the sharp apex point at the base of the bone in slice after slice, except perhaps for an occasional high intensity "blurb" very near the point of attachment.

And that's my question: Am I not looking at my images correctly? Am I mistaken feeling that the ligament isn't attaching properly?

Offline The KNEEguru

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Re: Seeking Help With Patellar Ligament Anatomy (MRI)
« Reply #1 on: July 09, 2018, 10:26:08 AM »
Hi
I will ask an expert colleague for his opinion and get back to you.
Sheila
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Offline haleba

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Re: Seeking Help With Patellar Ligament Anatomy (MRI)
« Reply #2 on: July 09, 2018, 08:16:52 PM »
Sheila,

Thanks for the quick reply. It would be nice to get some clarity on this.

Offline The KNEEguru

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Re: Seeking Help With Patellar Ligament Anatomy (MRI)
« Reply #3 on: July 10, 2018, 01:48:56 PM »
OK my colleague responded:
"Based upon the history and pain location as well at the MRI description, I think that it might be patella tendinopathy. The quadriceps muscle often responds by being relaxed and this causes the patellar tendon to be a little slack. Besides meniscus lesions are a common normal findings on MRI.
I would suggest new examination by a good doctor and Ultrasound, and if the diagnosis can be confirmed  Ultrasound guided steroid injection and slow high resistance physiotherapy guided training for several months."

I hope that helps a bit?
Sheila
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Offline Clarkey

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Re: Seeking Help With Patellar Ligament Anatomy (MRI)
« Reply #4 on: July 10, 2018, 06:50:38 PM »
Jumpers knee is needs to be treated with respect and caution that can rapidly change from acute to chronic if you pound the knee too much. Sounds like yours has reached to the chronic stage of pain and discomfort. My right knee problems has always been anterior pain and discomfort with patella tendonitis the main culprit to the knee pain.

Start conservatively before considering patella decompression surgery that can scar up the knee even more! Fat pad is closely linked to patella tendonitis is another underlying problem for my anterior pain that might have triggered off chronic patella tendonitis. Had an ultrasound guided cortisone injection for patella tendonitis, did not really make much difference. Everyone is different and might benefit you. Just need to be aware that it can weaken the cartilage! Have had 5 cortisone shots 3 of them in 2016 that might have caused a small lateral tear that was not spotted on my MRI scan.

I saw a sports medicine doctor that suggested going for ESWT for patella tendonitis. Had three sessions of Extracorporeal shock wave therapy (ESWT) followed by isometric holds exercises that can be very successful for many patients.

Good luck, hope you have success that can be achieve, can  takes what feels like forever to overcome patella tendonitis once it becomes chronic. Can be sorted at a very slow recovery rate. An OS with an interest in soft tissue problems is a good starting point, mine referred me to the sports medicine doctor before going for patella decompression surgery as the very last option after less invasive methods made no difference.

Some useful links.

https://nydnrehab.com/blog/how-isometric-exercises-can-reduce-tendon-pain/

https://www.sportsorthopaedicspecialist.co.uk/sports-injuries/patellar-tendonitis-jumpers-knee

Above link is UK based and should easily find ESWT in the USA. The OS that wrote about ESWT for patella tendonitis had the condition himself that worked for him.

[email protected]
« Last Edit: July 10, 2018, 06:58:44 PM by Clarkey »
RK: PFPS, Arthrofibrosis, Tendinopathy, Five cortisone injections
16/01/18 Anterior interval release, distal patella excision, lateral meniscal repair
18/07/14 Anterior interval release  
16/11/09 Medial plica excision, fat pad trimming

Offline haleba

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Re: Seeking Help With Patellar Ligament Anatomy (MRI)
« Reply #5 on: July 13, 2018, 10:44:11 PM »

Sheila,

This helps a lot!

Just skimming through the other postings I didn't have any trouble finding a couple of "ligament intact" (i.e. "nothing's wrong") type of findings for knee pain sufferers. That kind of dissonance is extremely hard to bear, making you wonder if the entire thing--pain and all--is an illusion.

Researching the details of patellar ligament attachment, I happened to see a front view photo of a patella stripped of ligament, saw how sharp a point the apex made and panicked because in the MRI the point looked like it was floating free and stabbing the Hoffa's pad. Reassuring myself that I should have been in a lot more pain if that were the case didn't help and I only calmed down when I took another look at the non-fat-suppressed PD (proton density) image and could trace a faint edge landing on the apex.

But your reply confirms there is a tendon where it should be, it just isn't showing up. Huge sigh of relief.

Following all this up took me on quite an anatomy tour.

One reason for my confusion is there are loads of examples hugely distorted knees that didn't always match my knee images (at first glance), but I found a few resources on what "normal" is to help finally clear my mind on this.

First, from Radsource's "Jumper's Knee" page:

"A normal patellar tendon should not exceed 7mm in AP diameter.", where "diameter" is used in the sense of "a straight line passing from side to side through the center of a body or figure[, especially a circle or sphere.]".

Double checking for the correct baseline, there were good illustrations in

"Patellar tendon analysis by ultrasound tissue characterization; comparison between professional and amateur basketball players. Asymptomatic versus symptomatic" Apunts: Medicina de L'esport, April - June 2017 (Apunts Med Esport. 2017;52(194):45-52)

"Changes in anteroposterior patellar tendon diameter support a continuum of pathological changes" [via ResearchGate] British Journal of Sports Medicine, May 2011 (Br J Sports Med. 2011 Oct;45(13):1048-51)

to verify that the measurement is done 90 to the length of the ligament. Using the Mango medical image analyzer, I chose lines on the sagittal PD and T1 images going from the base of the apex and grazing the curve of the tendon, with two perpendicular lines: L1, about 4.5 mm from the apex and L2, about 25 mm away from L1 (29 mm from the apex).

The final arrangement of measurement baselines is shown on the left side of the attached RKneeTendonDia_SagCor03-PD-FS_AxT1-FS.jpg. L1 is the top yellow line and L2 is the lower one. The measurements (in mm):

SeriesP1 DistP1-P2 DistL1 AngleL2 Angle AP Dia1AP Dia2
Sag PD FS4.35325.01890.335 89.9716.0354.062
Sag T1 FS4.48825.06990.128 90.4025.273.436


I noticed a couple of things in the reconstructed axial and coronal views underneath the baseline image. First, the crosshairs are touching the base of the apex, but in the small coronal image on the right there is a light-shaded gap above the dark tendon underneath, a good way to see any light/possibly damaged tendon that's shown in Figure 1 of "Association between obesity and magnetic resonance imaging defined patellar tendinopathy in community-based adults: a cross-sectional study" (BMC Musculoskeletal Disorders 2014 15:266 [Open Access]), that shows a "grey beard" of light tendon above the normal black. For some reason my coronal knee MRIs are chopped off behind the kneecap, so I couldn't verify for my case, except for the very low resolution reconstructed coronal images.

In the reconstructed axial image there's a grey "blob" on the back of the tendon. A zoomed-in view of a high resolution axial T1 series (the view to the right of the measurement baseline image), matched based on the femur outline shows a speckled area right behind the ligament that has a discernible edge connecting to the black ligament edges, possibly the boundary of the fat pad.

Unexpected confirmation of this came from Dr. Seong Jong Yun's "Increased signal intensity at the proximal patellar tendon: correlation between MR imaging and histology in eight cadavers and clinical MR imaging studies" from European Radiology, (Eur Radiol. 2015 Oct;25(10):2976-83 [via Semantic Scholar]). The full text is behind a paywall, but The Semantic Scholar page has all the figures and tables.

It took a few readings to understand, but Dr. Yun is describing a particular linear high intensity area that shows up behind the upper (proximal) ligament on some normal MRI scans (the multiple-arrowed locations in his images) that seems to correspond to the edge of the fat pad next to the grey triangular areas in his images, the implication being that the upper section tends to be interlaced with fatty tissue and blood vessels, causing a high intensity line behind the ligament.

I measured the grey triangular area on his second image making an 18 angle and set up a similar area on my image (the blue angled lines intersecting the yellow baseline in RKnee_SagT1-FS_AxT1-FS_Yun-pPT.jpg)

Estimated Hoffa's fat pad area (Yun)
Baseline coord. X dist. to skin  11.667
Baseline coord. X dist. to femur  28.333
Baseline coord. X dist. to est. HFP  4.167
Baseline coord. Y dist. to tendon left edge  7.2

and there is indeed a light-shaded streak (mixed in with others) that seems to follow the blue angle line on the right that Mango's ruler feature measures intersecting the green-dotted horizontal image crosshair 4.167 mm to the right of the top of the yellow baseline. In the high resolution axial image (lined up according to my marker dot measurements above) on the right, the back of the mottled area measures 4.249 mm from the scaled position (blue dot) of the crosshair position in the sagittal view. In succeeding lower slices in the axial image the area behind the ligament changes from mottled to grey-shaded and moves closer to the black ligament body.

All in line with the Radsource article:

" ... the normal patellar tendon demonstrates homogenous low signal intensity (4a). Exceptions to this rule occur proximally, where the posterior margin of the tendon may show thin, linear, intermediate signal intensity striations ..."

All as it should be? Maybe not.

Another thing that's kept me staring at these is that the whole area seems "busy" with what appear to be blood vessels (the study was done with and without gadolinium contrast) and more "lit up" in general, especially the fat pad area in front of the ligament (RKnee_SagT1-FS_SagPD-FS_Flame.jpg, two slices to the left of the baseline slice). This becomes more pronounced as you move to the left (medially) until there's a "blazing" spot right at the edge of the ligament (RKnee_SagPD-FS_Flame2.jpg, one additional slice to the left).

Probably reading too much into this, but I couldn't help noting from Yun's Table 6 on the "Involvement" line: "Focal area, especially posteromedial portion of pPT [proximal patellar tendon]" [my emphasis].

To cover all bases and be done with this one other thing some resources suggested checking is how high the patella is riding relative to its matching groove in the femur, in particular the Insall-Salvatti Index, suggested (by KneeGuru amongst others) being done at 30 knee flexion. My leg was only mildly flexed, but I'm justifying measuring the index based on

"The measurement of patellar height: A review of the methods of imaging" [via The Semantic Scholar] The Journal of Bone and Joint Surgery (Br), Vol. 92-B, No. 8, August 2010 (J Bone Joint Surg (Br) 2010;92-B:1045-53)

" ... the pioneering method of Insall and Salvati,12 published in 1971 with the development of a simple ratio between the length of the patellar tendon and that of the patella. It proved easy to measure on lateral radiographs, not requiring a fixed-flexion angle, and the mean normal ratio of 1.0 (0.8 to 1.2) is easy to remember."

In my case

Insall-Salvatti Index  48.027/44.276 = 1.084
Modified Insall-Salvatti Index  55.009/33.313 = 1.651
Patellotrochlear Index  17.059/33.313 = 0.512

Slightly on the low side of normal by Radsource's tabulation. Double checking the effect of knee flexion I found

"Variability of Measurement of Patellofemoral Indices with Knee Flexion and Quadriceps Contraction: An MRI-Based Anatomical Study" [via NCBI] Knee Surgery and Related Research, December 2016 (Knee Surg Relat Res. 2016 Dec; 28(4): 297301)

and their Table 1 shows a change of 0.04 in the Insall-Salvatti Index between the 30 flexed and extended knee, about a 2 mm difference in ligament length for my case.

Working through all this I found an extremely detailed MRI-based atlas of knee anatomy from a Colombian radiology interpretation service called SmartView titled "Normal MR Imaging Anatomy of the Knee" that's also viewable via Semantic Scholar, originally from Magnetic Resonance Imaging Clinics of North America, August 2011 (Magn Reson Imaging Clin N Am. 2011 Aug;19(3):637-53, ix-x).

I've gone from "mindless" pain and irritation to something resembling a reason why. Makes a world of difference. Thanks again!

« Last Edit: July 14, 2018, 02:48:51 AM by haleba, Reason: Minor edits »

Offline haleba

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Re: Seeking Help With Patellar Ligament Anatomy (MRI)
« Reply #6 on: July 14, 2018, 02:42:33 AM »
Clarkey,

Thanks for the input. Now that I'm approaching something resembling a workable (though tentative unofficial) specific diagnosis for the ligament injury I'm trying to fit this in with my other issues.

On top of the possible ligament strain, I have an apparent groin sprain that looks to have blossomed into biceps femoris tendonopathy (based on my aching butt :) that irritates my knees as well, and a massive Schmorl's node in my spine that's worrying me the most right now because it looks as if it almost penetrated the vertebra, so one bad fall could break it wide open.

I'm thinking a sports medicine doctor might be my best bet, figuring they might be better at dealing with multiple-area injuries and developing whole-body treatment/recovery plans: the last thing I want is a piecemeal approach that relieves one area at the expense of aggravating another.

As for surgery, until all of this happened I never fully comprehended that I've never had surgery aside from a couple of tooth extractions. Getting knocked unconscious and having someone cutting my body open is turning into a bit of a phobia that I'm trying to overcome since it looks like it may come to that, especially for the back injury.

So best believe I will thoroughly research that option.

Thanks