Bilateral Symptomatic Mucoid Degeneration of the Anterior Cruciate Ligament with Anterior Knee Pain but No Limited Knee Flexion

Abstract

Mucoid degeneration of the anterior cruciate ligament (ACL) is a rare cause of anterior knee pain (AKP). Some case reports have been published; however, it is difficult to diagnose and is often underdiagnosed or misdiagnosed because of its pathophysiological ambiguity. We report a rare case of a patient diagnosed with bilateral mucoid degeneration of the ACL with AKP and no limited joint range of motion (ROM). A 59-year-old man with spontaneous right AKP was admitted to our hospital. He first underwent arthroscopic resection of the thickened medial plica protruding far into the medial patellofemoral joint (PFJ) but felt little effectiveness thereafter. He then had an arthroscopic release of the lateral patellar retinaculum because of valgus knee and patellar instability, which resulted in only temporary improvement. Then, the AKP relapsed, this time with limitations in the ROM. Magnetic resonance imaging (MRI0 showed a diffuse, thickened ACL with a high inhomogeneous intensity in the T2-weighted and proton density weighted images and which looked similar to a celery stalk. Based on the patient’s history and MRI findings, we suspected mucoid degeneration of the ACL and subsequently performed arthroscopic excision. At the same time, AKP appeared on the other side. Since the MRI demonstrated a similar celery stalk image as before, the same operation was performed on this side, as well. Finally, AKP and the limitation of the ROM were relieved approximately one month after surgery. Due to the patient only suffering from AKP with a preserved ROM, it took about 14 months to diagnose this disease. It should, therefore, always be considered in cases of AKP alone.

Posterior tibial slope, notch width index and tibial tubercle to trochlear groove distance contribute to development of mucoid degeneration of the anterior cruciate ligament: a systematic review

“…Management options include non‐surgical measures such as oral analgesics and physiotherapy, whilst operative measures include partial resection of the area affected by degeneration, ACL reconstruction or total resection of the ACL [24, 26]. Whilst these options improve pain and range of motion, instability in the joint tends to appear years after the surgery, with an increased risk of rupture in patients who underwent partial resection [26]. Additionally, it is well known that there are increased psychological symptoms associated with delayed treatment of ACL injuries [21]; therefore, it is important to understand what factors predispose an individual to develop mucoid degeneration of the ACL so that those who are in need of treatment are monitored for early operative management if necessary.…”

“…Magnetic resonance imaging (MRI) is the gold standard for diagnosing mucoid degeneration of the ACL, and is characterised by a celery stalk sign, with subsequent diagnosis confirmed via tissue biopsy and histology [23]. Management options include non‐surgical measures such as oral analgesics and physiotherapy, whilst operative measures include partial resection of the area affected by degeneration, ACL reconstruction or total resection of the ACL [24, 26]. Whilst these options improve pain and range of motion, instability in the joint tends to appear years after the surgery, with an increased risk of rupture in patients who underwent partial resection [26].…”

Partial debridement is the most commonly reported treatment option for mucoid degeneration of the anterior cruciate ligament: a systematic review

“…There is often a limited range of motion with knee flexion with little to no deficit in knee extension [24]. Unfortunately, these associations are not sufficient to establish a diagnosis of MD‐ACL as this clinical vignette can mimic other conditions such as partial ACL tears, ganglion cysts, and synovial chondromatosis [30, 34]. Diagnosis is typically conducted through magnetic resonance imaging (MRI) showing increased ACL girth and increased signal intensity leading to a “celery stalk” appearance [34].…”