Inverted deltoid posterior cruciate ligament femoral insertion accompanied with medial synovial fold: a case of a complex posterior cruciate ligament anatomical variation recalcitrant to conservative treatment

Purpose The present study aims to report a symptomatic rare anatomical variation of the posterior cruciate ligament (PCL) that was encountered during arthroscopy. Case presentation A 34-year-old female suffered from dull anterior pain in the right knee, along with stiffness and the presence of an audible click and occasionally locking during deep knee flexion. Physical examination revealed only slight pain during single-leg squatting and mild knee effusion with painful limitation of the last degrees of flexion. Following unsuccessful conservative treatment, knee arthroscopy was performed in which the PCL was found to be hypertrophic, having a broad femoral insertion that almost completely occupied the intercondylar notch and impinged the anterior cruciate ligament. Moreover, the PCL presented a large medial synovial fold that formed a plica inserting to the medial meniscus's posterior horn. Ligamentoplasty was performed by excising one-third of the PCL lateral portion. The PCL medial synovial fold and the plica attaching to the medial meniscus were resected. The patient was allowed to return to full activity when her symptoms resolved, and the knee function was restored, at 5 weeks post-operatively. Conclusion The current study presented a rare and complex anatomical variation of the PCL that was symptomatic and recalcitrant to conservative treatment. Magnetic resonance imaging (MRI) can reveal the variant morphology of the PCL, and arthroscopy provides the definite treatment. This case report may be useful for orthopaedic surgeons and radiologists to consider anatomical PCL variations during differential diagnosis in patients with non-specific clinical presentation and findings.