Ganglion cysts are benign cystic masses that occur in association with musculoskeletal structures. The aetiology of ganglion cysts is controversial; however, it is generally thought to result from myxoid degeneration of connective tissue associated with joint capsules or tendon sheaths, to which the lesions are usually attached. They may occur in any part of the extremities within muscles, menisci, tendons or bones. Hereby, we present a rare case of intra-tendinous location of a ganglion cyst of the semimembranosus tendon occurring within the tendon substance itself. To date, there have only few cases reports in the literature reviewing intra-tendinous ganglion cysts occurred in the lower limbs.

Objective: To define the normal tibial tubercle to trochlear groove (TT-TG) distance in an adult Chinese population and to confirm that magnetic resonance imaging (MRI) measurements of TT-TG distance are reliable and reproducible. Methods: We conducted a retrospective review of MRI scans of 100 skeletally mature knees in an adult Chinese cohort from January 2015 to January 2016. Patients with MRI or clinical evidence of previous lateral patellar dislocation were excluded. TT-TG distance in MRI scans of normal knees was measured. Intraobserver and interobserver agreement was evaluated. Results: In our study, the mean normal value of the TT-TG distance in an adult Chinese cohort was found to be 10.36 ± 2.52 mm (men 10.92 ± 2.59 mm and women 9.67 ± 2.28 mm). Intraobserver and interobserver agreement regarding TT-TG distance measurement with MRI was excellent. Conclusion:This study can form the basis for future studies on the relationship between TT-TG distance and patellar instability in the adult Chinese population.