Post-ACL Reconstruction Cysts: Symptoms, Diagnosis, and Recovery - Orthopedics

Cyst after anterior cruciate ligament reconstruction?

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Hello, Doctor.
Last November, after school, I had an accident while riding my electric scooter and slipped on construction sand.
At that time, my backpack was heavy, and I was carrying other items.
I realized I was going to fall, and in the past, I would jump off and land safely, but this time I felt I couldn't land properly.
I thought about not injuring my head, so I jumped off while kneeling with my knees on the ground.
Later, I went to the emergency room for an X-ray, which showed no fractures, so I went home.
However, I continued to feel discomfort while walking, so I visited another hospital's orthopedic department.
Despite multiple X-rays showing no issues, my pain response was very intense.
After some time, in December, I had an MRI, which revealed tears in both the ACL and PCL, with the ACL being lax, a mild tear in the medial meniscus, and mild swelling in the knee joint.
In February, I underwent arthroscopy (I watched the procedure on the screen), and it confirmed the ACL tear with laxity, meniscus wear, and the PCL was normal.
The surgeon removed adhesions inside the knee.
The doctor suggested that reconstructing the ACL might not be the best option for me, so I was advised to try rehabilitation to see if it could alleviate the pain and allow the quadriceps to compensate for the ligament.
However, since I love running and playing basketball, I was very proactive in my rehabilitation, going almost every day.
After a month, I felt worse instead of better, and even walking became problematic.
Therefore, in April, I underwent ACL reconstruction surgery using a tendon from the back of my leg to replace the ACL.
I continued rehabilitation, and my range of motion improved, but I experienced quadriceps atrophy.

Since I am studying nursing, I had a two-week clinical internship at the beginning of August, during which I was walking quickly and assisting patients with getting into bed.
Sometimes, I was called to help with emergencies, which required me to run.
My internship hours were from 6:45 AM to 4:00 PM, with only 15-20 minutes for meals, and the rest of the time was spent standing, walking, running, and moving things.
After the internship, I noticed that my left leg (the one with the reconstructed ACL) was increasingly problematic, with more symptoms developing.
Besides experiencing sharp pain and numbness when touching the surface of my knee, my entire lower leg would also feel the same sharp pain upon touch.
Tapping the inner side of my knee would send pain down to my ankle.
I reported these issues to my doctor during follow-ups, but he couldn't determine the cause.
He reviewed the surgical process and confirmed there were no issues.
The area of sharp pain gradually extended from my knee to my toes.
In September, my doctor asked me to recount the entire progression of my symptoms.
After listening, he tapped three specific areas: the middle of my knee, just below the inner side of my knee, and below the knee.
All these areas were extremely painful upon light tapping, extending to my ankle.
He mentioned he had an idea of what it might be, though he thought the likelihood was very low.
He said all the symptoms matched, and once we could confirm an MRI, he would let me know (at that time, I was unable to get an MRI due to insurance issues).
We also noted that it had been quite some time since April, which we both found strange.
I had seen a neurologist, and had CT scans of my brain, thyroid tests, and lumbar MRI, all of which showed no significant abnormalities, just mild issues at most.
Therefore, the doctor administered anti-inflammatory and pain relief injections in those three areas, which were very deep and painful.

Finally, I had the MRI at the end of October, which revealed a white mass in front of the ACL, indicating inflammation.
As I scrolled down, I noticed another mass, both the inflammation and the mass were located in front of the ACL.
He said it matched his initial thoughts, noting it was very rare and typically occurs in patients post-reconstruction.
However, he had previously operated on a case that was larger than mine.
The doctor stated that a small incision with arthroscopy could remove it, and it was highly likely that this mass was causing my leg's gradual abnormality.
A few days later, I underwent surgery.
I received a spinal block but did not watch the procedure.
Afterward, the doctor informed me that the mass had been removed, but he found some damage and inflammation in the meniscus, reconstructed ACL, and surrounding tissues, all of which were addressed with arthroscopy.
The nurse asked if I wanted the mass to be tested, but the doctor said it was unnecessary.
He then recommended another PRP injection to promote faster healing and ensure recovery in the knee joint.
The day after surgery, after removing the drainage tube, I received the PRP injection.

Indeed, a few days after the surgery, my knee surface gradually returned to normal, and the symptoms in my lower leg improved significantly, although some persisted.
The resident physician specifically mentioned that the mass was a cyst formed due to inflammation, advising me to avoid putting weight on my knee for the next few days.
During a follow-up visit, I was shown the arthroscopy images, revealing some wear on the reconstructed ACL, but everything had been addressed.
After returning home from the follow-up, while organizing insurance documents, I discovered three diagnoses: 1.
Synovitis post-ACL reconstruction (discharge diagnosis plan), 2.
Spontaneous rupture post-ACL surgery (discharge nursing education document), and 3.
Ligament wear post-ACL surgery (diagnosis certificate).
The doctor had indeed mentioned synovitis before, which I understood, but the other two diagnoses were different.
However, when combined, they made sense, but separating them made it difficult for insurance purposes.
Therefore, I researched the mechanism of post-operative synovitis and came across an article about PVNS (pigmented villonodular synovitis).
This piqued my curiosity, and I investigated the condition, finding that it matched my symptoms.
However, since the cyst was discarded without testing, I don't know if it was indeed PVNS.

My main question is whether, if it is simply synovitis or truly PVNS, rehabilitation and rest for a while will allow me to return to running and playing basketball without easily triggering a recurrence of the cyst due to inflammation.
I really enjoy running and playing basketball, but I haven't done so for a year.
In December, I noticed that running would cause my left knee to feel numb, gradually extending to my lower leg, and if I continued running, my entire leg would feel weak (which I have experienced before).
Consequently, I have been hesitant to engage in any activities that might harm my knee.
Because of this, I have undergone three arthroscopic surgeries this year.
I understand the situation, but I am curious about the possibility of PVNS regarding the cyst.
If it is indeed suspected, I wouldn't blame the doctor for not testing it at the time, but I am a bit curious about it.
Since my next follow-up appointment is still a long way off, I wanted to ask for your thoughts on this matter.
Thank you, Doctor.
🙏

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Jin, 10~19 year old female. Ask Date: 2023/11/19