155. What is a Baker's Cyst?

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In this episode of PT Snacks podcast, host Kasey delves into Baker's Cysts, explaining what they are, how they form, and why they occur. You'll learn about the anatomy of the knee joint, the role of synovial fluid, and the common knee conditions that can lead to the development of these cysts. Learn insights on how to diagnose Baker's Cysts and discusses various treatment options, including conservative management techniques and when to consider more invasive procedures. Whether you're a physical therapist or a student, this episode provides valuable knowledge to enhance your practice.

00:00 Introduction and Podcast Overview

00:39 Understanding Baker's Cysts

02:38 Causes and Symptoms of Baker's Cysts

05:31 Diagnosis and Treatment Options

08:15 Conclusion and Additional Resources

Handy JR. Popliteal cysts in adults: a review. Semin Arthritis Rheum. 2001;31(2):108‑118. doi:10.1053/sarh.2001.27659 

Herman AM, Marzo JM. Popliteal cysts: a current review. Orthopedics (Healio Org). 2014;37(8):e678‑e684. doi:10.3928/01477447‑20140728‑52 

Frush TJ, Noyes FR. Baker’s cyst: diagnostic and surgical considerations. Sports Health. 2015;7(4):359‑365. doi:10.1177/1941738114545547 

Zhou XN, Li B, Wang JS, Bai LH. Surgical treatment of popliteal cyst: a systematic review and meta‑analysis. J Orthop Surg Res. 2016;11:22. doi:10.1186/s13018‑016‑0356‑3 

Lyalina VV, Skripnichenko EA, Borisovskaya SV, Nikitin I. Baker’s cyst: etiopathogenesis, clinical picture, differential diagnosis of complications‑‑a review. 2023. 

Transcript

0:30

Hey guys. Welcome to PT Snacks podcast. This is Kasey, your host, and if you're tuning in for the very first time, what you need to know is that this podcast is meant for physical therapists and physical therapist students who are looking to grow your fundamentals and by segments of time. Now, today we are going to talk about what Baker's Cysts are, but before we do, if you've listened to at least three episodes of the show and you've found it to be helpful, if you wouldn't mind just pausing and leaving a brief review wherever you listen to this, that really does make a huge difference in helping the show to grow and if you have already done so. Thank you. I really appreciate you. Now, today we're gonna talk about something called Baker Cysts, because if you come anywhere close to a knee. I probably had a patient maybe have this come up on their imaging or they've talked about it. You might be wondering, what is this? What do I do about this? So that's what we're gonna talk about today. What exactly is a baker cyst? How does it happen? And what do we do about it? So let's start with basics. So a Baker cyst is a fluid-filled swelling that forms at the back of the knee in a space called the Pop Lial fossa. So that's why Baker Cyst can also be known as a Pop Lial cyst because of the location of where it's at. It's usually caused by extra synovial fluid, which is the lubricant in our joints and that extra synovial fluid gets trapped in a small pocket behind the knee. More specifically, the cyst forms when fluid pushes into a structure called the gastroc anemia, semimembranosus bursa. Which is a really long name. The bursa sits between the medial head of the gastroc and the semimembranosus tendon. So the bursa is literally named for where it is in a lot of people, especially adults with chronic knee conditions. This bursa is connected to the joint capsule through a natural opening. So the interesting thing about this bursa is that. There is an opening that acts like a one-way valve. So when intraarticular pressure rises maybe either from injury or inflammation, the joint fluid actually gets pushed out through the capsule and into the bursa. And because of the valve like anatomy, the fluid can't easily flow right back in. So what happens is it accumulates and then that accumulation leads to a visible or palpable cyst on the back of the knee. A KAA Baker cyst. Now let's talk about something important. Why is this happening? Why doesn't everybody have a baker cyst? In adults, the most common things that irritate or damage the joint and lead to chronic joint infusion like osteoarthritis, minuse tears, or rheumatoid arthritis. Can cause this to happen so the joint can get inflamed, makes too much fluid, and then that fluid has to go somewhere, right? So the body doesn't want pressure to just keep on building inside the capsule so that extra fluid is gonna escape and then get trapped. Some literature suggests that this could be even a protective mechanism, like the cyst could just function as a pressure relief valve for the knee joint, but what we do know is that when the cyst becomes large and inflamed or ruptures, it can cause its own set of problems. Now, kids can have this too, but it's a little bit different. Pediatric baker cysts aren't usually caused by joint disease. They're usually often just small out pouching of the synovial lining, usually painless and can go away on their own, but don't require a lot of intervention unless it's symptomatic. So now that we know why it forms, let's talk about who gets them. So I just mentioned conditions that can cause this. So you can imagine that baker cysts are common in middle age and older adults, especially those with knee osteoarthritis or minuscule injuries. Studies can show that 20 to 40% of people with NEO A also have a baker cyst, even if it's asymptomatic, and the prevail increases with the severity of the joint degeneration. They can also be seen with inflammatory conditions like RA or post-injury where chronic swelling is present. So what does a baker cyst feel like for the patient? Some are asymptomatic and found incidentally on imaging. Others can give patients a feeling of tightness or swelling behind the knee, especially with activities that involve full flexion or full extension, and larger cysts can become uncomfortable and limit motion and even cause a noticeable bulge in the popal space. In the events that a cyst ruptures, it can mimic a deep vein thrombosis. So patients may report sudden calf pain, swelling, redness, or even describe it as a bursting or kind of feeling like water running down the leg sensation that makes diagnosis important. So we wanna use imaging to confirm,'cause we. I definitely don't wanna mess around with a deep vein thrombosis that's untreated. So an ultrasound can be really helpful for identifying CYS quickly and ruling out A DVT. And then an MRI is helpful for evaluating underlying joint pathology and the cys full extent. Now as physical therapists, what do we do about it? So the key principle here is that the cyst is a symptom, not necessarily always the primary issue. Most Baker cysts are secondary to a knee issue, so the treatment has to address the underlying pathology, meaning that if it's a knee issue that's causing it to happen, we need to treat that issue. So that might mean managing osteoarthritis conservatively with strength and mobility as needed. If there's a meniscal tear, treating that working to reduce joint inflammation or effusion. And often patients are gonna go through conservative treatment first, so that might be activity modification to help manage the amount of swelling that's happening. Some, a lot of patients will go through NSAIDs or corticosteroid injections if inflammation is pretty significant. Again, thinking about why Baker cyst happened in the first place. That should make sense. And then physical therapy to optimize their ability to do what they need to do to help build up resiliency in that joint so that it's not getting to the point where it's flared up and inflamed. Now, beyond strengthening, yes, you can use manual therapy. Quad and hamstring strengthening. If they are having issues with gait mechanics or mobility functional mobility, that kind of stuff. Yeah. Meet the needs of your patients, see what they're having issues with, and try and build a bridge to where they wanna go. But if they're, in some cases, if it's. Pretty significant. Doesn't seem to be going away. A cyst can be drained, especially under ultrasound guidance. And sometimes that is then followed by a corticosteroid injection, but that's usually temporary unless the underlying joint condition is treated. So don't necessarily just wanna do an injection in isolation. Surgery is pretty rare, but it can be considered if the cyst is pretty large or symptomatic. And if there's a clear mechanical source, like a minuscule tear, that can be addressed. Arthroscopically too. So ideally, as we're managing stress as the therapist, this in turn should help to allow the cyst to resolve or shrink once the joint is under control. As a recap, a baker cyst is a fluid filled sac behind the knee caused by joint effusion. It forms a one-way valve mechanism behind the knee joint and the gastro anemia em Brunos bursa, and it's often secondary to joint conditions like OA or a meniscal injury. Treatment typically focuses on the knee, not just the cyst with conservative rehab as the first line of defense. And yes, sometimes it can go away on its own. So that's it for today, guys. If you have any questions, you can hit the, send me a text link below in the show notes, or just shoot me an email below. It's in below in the show notes as well. If you have any requests for future episodes, I'm also all ears. Now on another note, med Bridge is actually offering listeners over a hundred dollars off just for being a listener of this show. So you can get your promo code below in the show notes for if you're a pre clinician or if you're a student, you get an even better deal. But if you're not sure what exactly Med Bridge is, it's basically a company that offers tons of CEU courses, webinars, and even specialty exam prep courses. If you're studying for your OCS or SS. And within that you even get practice tests and you can get your eyes used to looking at a screen for a long period of time because that test can be a little brutal. But other than that, I hope you guys have a great rest of your day, and until next time.