Anterior Cruciate Ligament (ACL) Mucoid Degeneration
AnatomyAnterior Cruciate Ligament, is an important structure of the knee joint. Anatomically, it is arranged in a crossed pattern with the Posterior Cruciate Ligament, forming an 'X', therefore, it is also known as cruciform ligament. This ligament consists of two fibers, mainly, the anterio-medial and postero-lateral fibers, respectively. The ligament is mainly responsible for restraining anterior translation of knee. Along with that, it also controls the internal rotation. Therefore, Anterior Cruciate Ligament tear is more susceptible during any injury to the knee. The cruciate ligament have mechanoreceptors, which are responsible to detect any change in position of the knee, direction, speed and tension. It is lined by the synovial fluid, which provides the nutrition and plays an integral part in healing.
What is Anterior Cruciate Ligament Mucoid Degeneration?
This is a rare pathological condition, in which, there is increased signal from within the ligament. Mucoid degeneration, is the irreversible degeneration of the tissue with the infiltration of mucin(glycosaminoglycans) within the fibers. Multiple theories have been put forth that explains the pathological disorganization in the collagen fibers of the Anterior Cruciate Ligament, such as synovial, traumatic, and degenerative, "Synovial” theory- states that there is accumulation of synovial fluid inside the substance of ACL in a herniated pouch of synovium. "Traumatic” theory - post injury, ACL fibroblasts secrete glycosaminoglycans, the mucin substance within the ACL. Other theories include “Degenerative” theory- MD could occur due to ageing.
- Painful terminal knee flexion
- No instability
- No extension block
- Joint line tenderness
- Posterior knee pain
- Difficulty in climbing stairs, cross-leg sitting, squatting
- Acute/Repeated Trauma
- Primary condition- Osteoarthritis, degenerative menisci, meniscal tear, Meniscectomy
- Impingement of the soft tissue in the vicinity
- Ganglionic cyst
- Tendon tear/ Tendon rupture
- Characteristic: "celery stalk" appearance, reflects ACL degeneration.
- Ligaments and tendons are accumulated by mucoid change might display a thickened and/or hypertrophied appearance, with an increase in signal intensity.
- Narrowing of the intercondylar notch
- Sometimes, it is mislead as ACL tear on MRI findings, hence requires probing and histopathology for definitive diagnosis.
- Arthroscopically ACL is intact but fibrillated, yellowish and hypertrophied, with interspersed yellowish mucinous material along the fibers, lack of synovial linning of the ACL
Conditions that resembles the clinical findings are:
NSAIDS and Physiotherapy
- Partial/Total ACL resection arthroscopically- There is marked improvement in the range and reduced posterior pain, but at the cost of increased post-operative knee laxity.in some cases, and may lead to instability. The prognosis depends upon the age of the patient, and the associated injuries
- Arthroscopic debridement
- Wear knee brace
- Initially, partial weightbearing is allowed.
- ACL reconstruction rehabilitation protocol is followed.
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