Gerdy's tubercle is the bony bump on the outer side of the tibia bone just below the knee joint, and to which attaches the iliotibial band and tensor fascia lata.
A line perpendicular from the lateral epicondyle, should bisect the line drawn between Gerdy's tubercle and the head of the fibula.
Gerdy's tubercle is the attachment site of the iliotibial band.
Gerdy's tubercle is an important landmark
The surgeon uses this landmark when deciding where to position the incision for surgery to the posterolateral corner and the lateral meniscus, and indeed all surgery in the upper lateral tibia, in order to avoid damage to the common peroneal nerve in that area.
Gerdy's tubercle: the lighthouse to the knee. Donegan DJ, Seigerman DA, Yoon RS and Liporace FA. J Orthop Trauma. 2015 Feb;29(2):e51-3. doi: 10.1097/BOT.0000000000000196.
Gerdy tubercle osteotomy in surgical approach of posterolateral corner of the knee. Garofalo R, Wettstein M, Fanelli G and Mouhsine E. Knee Surg Sports Traumatol Arthrosc. 2007 Jan;15(1):31-5. Epub 2006 Sep 2.