Anterior Cruciate Ligament Ganglion and Decompression of Mucoid Degeneration Using a “Figure-of-4 Position”

Anterior cruciate ligament (ACL) ganglion cysts and mucoid degeneration of the ACL are 2 distinct nontraumatic lesions of the ACL that occur discretely but can coexist. The exact etiopathogenesis still needs to be clarified. Mucoid degeneration presents as pain mainly on the posterior or posterolateral aspect of the knee and loss of terminal flexion and extension range of motion of the knee. There are several methods of treatment, including ultrasound-guided decompressions and arthroscopic decompression procedures. Arthroscopic decompressions include resecting the most affected posterolateral bundle and complete takedown of the ACL, with or without notchplasty. The reason for flexion deficit is the femoral-sided thickened ACL tissue (mucoid degeneration of the ACL) or the presence of a ganglion cyst. The impinging tibial insertion ganglion, the anvil osteophyte, or the thickened tibial stump of the ACL cause the extension deficit. Hence, addressing both anterior and posterior compartments is necessary for complete decompression. This Technical Note gives a stepwise approach to bicompartmental decompression using only anterior portals with the figure-of-4 positions.