Sesamoiditis of the cyamella: imaging features of this rare presentation

Abstract

We report a unique case of sesamoiditis in an extremely rare accessory genicular ossicle. Common to lower primates, the cyamella or popliteus tendon sesamoid bone is usually absent in humans. A 19-year-old male sustained a twisting injury to the right knee and presented with mechanical symptoms of knee pseudo-locking. A plain radiograph of the knee illustrated the presence of a cyamella. Magnetic resonance imaging demonstrated marked bone marrow oedema of this sesamoid structure and in the adjacent popliteus tendon. To our knowledge, documented sesamoiditis of this osseous structure on radiological imaging has not been published in English literature and this case highlights the imaging features of this uncommon entity.

Cyamella (a popliteal sesamoid bone) prevalence: A systematic review, meta‐analysis, and proposed classification system

“…Qualitative results : The majority of the studies included in the qualitative synthesis (11/15) were published within the last 15 years (Akansel et al, 2006; Corvalan et al, 2018; Dheer et al, 2012; Duarte et al, 2017; Dykes & Vijay, 2014; Galifi, 1950; Khanna & Maldjian, 2014; Mishra & Jurist, 1996; Munk et al, 2009; Pearson & Davin, 1921a; Reddy et al, 2007; Rehmatullah et al, 2014; Siefferman & Sheth, 2012; Slanina, 1956; Thomas, 2018), highlighting a recent surge in interest in the cyamella. Two studies were carried out with the intention of identifying cyamellae, and 13 studies were case reports, where cyamellae were discovered incidentally.…”

“…(a) A painful cyamella presented with a bone marrow edema‐like signal within the cyamella and the adjacent femoral condyle, which may have be due to repetitive micro‐trauma/friction between the cyamella and the femoral condyle, or a transient dislocation of the popliteus tendon/cyamella, which spontaneously reduced prior to evaluation (Dheer et al, 2012). (b) A painful cyamella exhibited sesamoiditis after a traumatic twisting injury to the knee during sports activity (Dykes & Vijay, 2014). Two patients had pain after (c) possibly dislocating their cyamella (Mishra & Jurist, 1996) and (d) developing popliteal tendinitis following a twisting injury (Rehmatullah et al, 2014) (which may have been unrelated to the cyamella).…”

“…As two of the studies reported the cyamella to be painful after a twisting injury, and one of the actions of the popliteus muscle is to laterally rotate the femur on the tibia, it is possible that excessive twisting overload the popliteus, consequently damaging the cyamella. When treatments were discussed, cyamellae were generally treated conservatively (Khanna & Maldjian, 2014; Mishra & Jurist, 1996; Rehmatullah et al, 2014) but one was surgically removed after non‐operative routes proved ineffective (Dykes & Vijay, 2014).…”

“…Class I cyamellae were found lateral to the lateral femoral condyle but proximal to the tibial plateau, near the origin of the popliteal tendon and often within the popliteal sulcus (7/20, 35%) (Figure 4). They are likely embedded in the origin of the popliteal tendon (Corvalan et al, 2018; Dykes & Vijay, 2014). Class II cyamellae were lateral to the tibial condyle, proximal to the fibular head and near the tibial plateau (8/20, 40%) (Figure 1).…”

Coexistence of symptomatic cyamella and multiple fabellae: A case report

“…The cyamella, an ossified cartilaginous body within the proximal tendon or at the musculotendinous junction of the popliteal muscle, is a rarely observed and generally asymptomatic sesamoid bone of the knee. [1][2][3][4] The prevalence of ossified cyamella is reported to be between 0.57 and 1.8%. 3 A symptomatic cyamella is very rare and described in the literature only in few case reports.…”