Answer for BIR CoW 26 Oct 2025
MUCOID DEGENERATION OF ACL AND RIGHT PROXIMAL TIBIAL ENCHONDROMA
Findings
Thickened high signal intensity anterior cruciate ligament with fibers continuity appears intact. Giving the appearance of celery stalk sign Well defined lobulated intramedullary metadiaphyseal lesion in the proximal tibia appearing heterointense with osseous and chondral components showing rings and arc pattern Impression: Mucoid degeneration of anterior cruciate ligamenT (ACL). Features of right proximal tibial enchondroma.
Discussion
Mucoid Degeneration of ACL: Mucoid Degeneration of ACL is an uncommon condition that leads to knee pain and discomfort, primarily impacting individuals in their fourth decade of life. Kumar et al. initially coined the term mucoid cystic degeneration to describe this condition affecting the ACL. It is characterized by significant disruption of the ligament's normal appearance and can contribute to knee pain. The predominant symptom associated with MD of ACL is knee pain, primarily located in the posterior aspect. This pain is caused by mechanical impingement on the posterior cruciate ligament and the posterior capsule or bone erosions. Additional clinical manifestations include a mechanical hindrance to extension, varying degrees of swelling, and audible clicking sounds. MRI serves as a valuable tool for evaluating MD of ACL during preoperative assessment. It shows an ACL that is indistinctly defined, exhibiting an enlarged dimension while retaining a typical orientation, and presenting heightened signal intensity interspersed among visible intact ACL fibers, creating a distinctive "celery stalk" appearance. On T1-weighted images, MD of ACL typically appears with intermediate signal intensity, while on T2-weighted images, it shows high signal intensity. Hodler et al. correlated MRI appearances with histological findings and found that 29 out of 38 ligaments had focal areas of signal increase, suggesting a correlation between the focal MRI signal changes and the presence of degenerative changes in the ligaments Arthroscopic observations suggest that MD of ACL involves a hypertrophied, fibrillated ligament with the presence of yellowish mucinous material interspersed among the fibers. This is often accompanied by the absence of the ligamentum mucosum. Additionally, a lack of smooth synovial lining is typically noted. Arthroscopic surgery is a discretionary treatment option for MD of ACL. This procedure involves the partial removal of lesions within the ACL, leading to rapid pain relief and improved range of motion, without any persistent symptoms of instability. The reduction in volume and tension within the ACL is often attributed to the notable pain relief. Debridement of mucinous substance, along with partial resection of ACL, is a recommended and effective therapy that does not cause instability, according to many authors ENCHONDROMA Enchondromas are considered a “cartilage rest”. Hence the close relation to the epiphyseal growth plate, often within 2 cm. These benign lesions occur as incidental findings in 3% of all knee MRIs and need no follow up. Enchondromas may slowly grow over time or even regress in size. Growth itself is not a sign that the lesion has become malignant. Enchondromas are typically smaller than 5 cm and 80% of enchondromas in the long bones is smaller than 2 cm. Variable size cut offs are proposed to differentiate enchondroma from Atypical Cartilaginous Tumour and chondrosarcomas. Two syndromes are associated with multiple enchondromas: Ollier disease Maffucci syndrome Enchondromas are typically located in a central or eccentric position within the medullary cavity of tubular bones: Small tubular bones of the hands and feet (~50%) -Proximal phalanx most common Large tubular bones - E.G. Femur, tibia, humerus
REFERENCES:
1.Mucoid Degeneration of the Anterior Cruciate Ligament: A Case Report https://doi.org/10.7759/cureus.50545
2.Mucoid degeneration of the anterior cruciate ligament: MRI, clinical, intraoperative, and histological findings. Makino A, Pascual-Garrido C, Rolón A, Isola M, Muscolo DL. Knee Surg Sports Traumatol Arthrosc. 2011;19:408–411. doi: 10.1007/s00167-010-1239-5.
3.Rasuli B, Gaillard F, Bell DJ. Enchondroma, Radiopaedia, Radiology Reference Article. Available from: https:// www.radiopaedia.org/articles/enchondroma .
4.Cartilage tumors with special attention to Atypical Cartilaginous Tumors - Kirsten van Langevelde and Robin Smithuis
Findings
Thickened high signal intensity anterior cruciate ligament with fibers continuity appears intact. Giving the appearance of celery stalk sign Well defined lobulated intramedullary metadiaphyseal lesion in the proximal tibia appearing heterointense with osseous and chondral components showing rings and arc pattern Impression: Mucoid degeneration of anterior cruciate ligamenT (ACL). Features of right proximal tibial enchondroma.
Discussion
Mucoid Degeneration of ACL: Mucoid Degeneration of ACL is an uncommon condition that leads to knee pain and discomfort, primarily impacting individuals in their fourth decade of life. Kumar et al. initially coined the term mucoid cystic degeneration to describe this condition affecting the ACL. It is characterized by significant disruption of the ligament's normal appearance and can contribute to knee pain. The predominant symptom associated with MD of ACL is knee pain, primarily located in the posterior aspect. This pain is caused by mechanical impingement on the posterior cruciate ligament and the posterior capsule or bone erosions. Additional clinical manifestations include a mechanical hindrance to extension, varying degrees of swelling, and audible clicking sounds. MRI serves as a valuable tool for evaluating MD of ACL during preoperative assessment. It shows an ACL that is indistinctly defined, exhibiting an enlarged dimension while retaining a typical orientation, and presenting heightened signal intensity interspersed among visible intact ACL fibers, creating a distinctive "celery stalk" appearance. On T1-weighted images, MD of ACL typically appears with intermediate signal intensity, while on T2-weighted images, it shows high signal intensity. Hodler et al. correlated MRI appearances with histological findings and found that 29 out of 38 ligaments had focal areas of signal increase, suggesting a correlation between the focal MRI signal changes and the presence of degenerative changes in the ligaments Arthroscopic observations suggest that MD of ACL involves a hypertrophied, fibrillated ligament with the presence of yellowish mucinous material interspersed among the fibers. This is often accompanied by the absence of the ligamentum mucosum. Additionally, a lack of smooth synovial lining is typically noted. Arthroscopic surgery is a discretionary treatment option for MD of ACL. This procedure involves the partial removal of lesions within the ACL, leading to rapid pain relief and improved range of motion, without any persistent symptoms of instability. The reduction in volume and tension within the ACL is often attributed to the notable pain relief. Debridement of mucinous substance, along with partial resection of ACL, is a recommended and effective therapy that does not cause instability, according to many authors ENCHONDROMA Enchondromas are considered a “cartilage rest”. Hence the close relation to the epiphyseal growth plate, often within 2 cm. These benign lesions occur as incidental findings in 3% of all knee MRIs and need no follow up. Enchondromas may slowly grow over time or even regress in size. Growth itself is not a sign that the lesion has become malignant. Enchondromas are typically smaller than 5 cm and 80% of enchondromas in the long bones is smaller than 2 cm. Variable size cut offs are proposed to differentiate enchondroma from Atypical Cartilaginous Tumour and chondrosarcomas. Two syndromes are associated with multiple enchondromas: Ollier disease Maffucci syndrome Enchondromas are typically located in a central or eccentric position within the medullary cavity of tubular bones: Small tubular bones of the hands and feet (~50%) -Proximal phalanx most common Large tubular bones - E.G. Femur, tibia, humerus
REFERENCES:
1.Mucoid Degeneration of the Anterior Cruciate Ligament: A Case Report https://doi.org/10.7759/cureus.50545
2.Mucoid degeneration of the anterior cruciate ligament: MRI, clinical, intraoperative, and histological findings. Makino A, Pascual-Garrido C, Rolón A, Isola M, Muscolo DL. Knee Surg Sports Traumatol Arthrosc. 2011;19:408–411. doi: 10.1007/s00167-010-1239-5.
3.Rasuli B, Gaillard F, Bell DJ. Enchondroma, Radiopaedia, Radiology Reference Article. Available from: https:// www.radiopaedia.org/articles/enchondroma .
4.Cartilage tumors with special attention to Atypical Cartilaginous Tumors - Kirsten van Langevelde and Robin Smithuis
Note:
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!