A 36-year-old male patient presented with knee pain and stiffness, progressively increasing over the last 6 months.
A 36-year-old male patient presented with right knee pain and stiffness, progressively increasing over the last 6 months. There was no history of trauma or any symptoms suggestive of infection. No history of locking or clicking sensation within the joint was reported. On clinical examination, no overt joint swelling or joint tenderness was seen. The anterior and posterior drawer test, Lachmans test and Mc Murray test were negative. There were no findings favouring a joint effusion. Patient could not completely flex or extend the knee.
Plain skiagram of the knee did not convey new findings. The patient was advised to have MRI performed for further evaluation. On MR, the ACL was thick, ill-defined and enlarged in size. On proton density weighted sagittal image there was homogeneous increased signal intensity within the enlarged and thickened ACL. The individual fibres appeared to be intact, but spread apart on the proton density and STIR sequence, similar in appearance to that of a "celery stalk". No intra-osseous signal alteration was seen at the tibial or femoral attachment of ACL. The PCL, collateral ligaments and menisci were normal. Mild joint effusion was also present. Based on the imaging findings, diagnosis of an ACL ganglion cyst (mucoid degeneration) was made.
Anterior and posterior cruciate ligament ganglion cysts are reported in the literature as being rare with an incidence of approximately 0.5% to 1%. The etiopathogenesis of cruciate ligament ganglion cysts is uncertain. Various theories which have been postulated include: [1] senescent mucinous degeneration of the ligament, [2] proliferation of congenitally entrapped synovium within the ligament, and [3] sequelae of remote ligamentous trauma.
Two characteristic MR appearances have been described for ganglion cysts of the ACL. The first presents as a discrete fluid signal cystic lesion within the substance or on the surface of the ACL. The second form has been compared to a “celery stalk” in appearance. The ACL demonstrates diffuse thickening containing ill-defined intraligamentous T2-hyperintensity, which splays the intact ACL fibres. This occurs due to accumulation of amorphous mucoid matrix which gets deposited between intact and almost parallel ACL fibres.
The thickening and increased signal intensity along the course of the ligament may be confused with the appearance of an ACL tear. Few important distinctions allow a confident diagnosis of an ACL ganglion cyst. In case of cruciate ligament ganglia, intact ACL fibres can often be visualised coursing through or around the cyst. Additionally, the ancillary MR findings of an ACL tear, such as bone bruises, buckling of PCL and the forward subluxation of tibia, are absent. Patient’s clinical history and clinical examination do not support an ACL injury. Lachman test for AC instability is negative.
Patients may be asymptomatic; and these ganglion cysts may be diagnosed incidentally on imaging. In symptomatic patients knee pain is the most common complaint at presentation. Larger ganglia may cause stiffness and restriction of movement.
Incidentally detected and asymptomatic cruciate ligament ganglion cysts do not need any intervention. In symptomatic patients arthroscopic decompression of the ganglion or resection is helpful in relieving the patient of the symptoms.
Ganglion cyst (mucoid degeneration) of the ACL
Based on the provided MRI images of the knee joint, a localized abnormal signal can be observed in the region of the anterior cruciate ligament (ACL). This presents as a cystic lesion with high signal intensity on T2-weighted images, appearing in a cord-like or “celery stalk” (celery stalk sign) shape, with mucinous signal deposition seen between the ligament fibers. The ligament fibers appear continuous overall, showing no obvious signs of rupture. Other knee structures (such as the posterior cruciate ligament, meniscus, and cartilage surfaces) show no significant abnormal damage. No apparent bone contusion, fracture, or marked bony deficiency is observed in the joint space.
Considering the patient’s age, clinical symptoms (chronic knee pain, limited range of motion without obvious instability), and the MRI features (a cystic lesion with high T2 signal within the ACL, intact ACL fibers, and no signs of bone contusion or ligament tear), the most likely diagnosis is Ganglion Cyst of the Anterior Cruciate Ligament (ACL ganglion cyst).
1. Treatment Strategy:
For patients with mild symptoms or for incidental findings without significant clinical symptoms, conservative treatment is typically considered, including non-steroidal anti-inflammatory drugs (NSAIDs) for pain relief, physical therapy, and follow-up monitoring.
For those with significant symptoms where pain and joint mobility do not improve with conservative management, arthroscopic surgical treatment may be considered, including cyst decompression or excision. This often effectively relieves symptoms and improves joint function.
2. Rehabilitation and Exercise Prescription (FITT-VP Principle):
(1) Frequency: Depending on the patient’s postoperative or conservative treatment condition, perform specialized knee joint functional training 3–5 times per week.
(2) Intensity: Start at a low intensity and progress gradually. Early stages can include eccentric and isometric exercises to avoid excessive stress on the ACL.
(3) Time: Each training session lasts about 20–30 minutes. As the condition or rehabilitation progresses, the duration may be extended to 30–45 minutes.
(4) Type: Include the following training methods:
• Range of Motion (ROM) training: Combine passive and active movements, gradually increasing the range of motion.
• Muscle Strength Training: Early stages can focus on straight leg raises and quadriceps contractions, progressing later to half squats and seated leg presses with resistance.
• Balance and Proprioception Training: Examples include balance board exercises to enhance knee joint stability.
(5) Volume/Progression: As knee stability and muscle strength improve, gradually increase the load (e.g., adding resistance bands or ankle weights) and lengthen training time. Monitor knee pain and swelling closely.
(6) Personalization: Adjust individually according to the patient’s specific recovery process and physical condition (e.g., baseline muscle strength, cardiorespiratory fitness). If there is noticeable discomfort, worsened pain, or joint swelling, seek medical advice promptly and modify the training plan.
This report is a reference medical analysis based on the information currently provided and does not replace an in-person consultation or professional medical advice. If there is any change in the patient’s condition or any questions, it is recommended to seek medical care promptly and discuss further with healthcare professionals.
Ganglion cyst (mucoid degeneration) of the ACL
