Arthroscopic Approach to the Subextensorius Recess of the Lateral Femorotibial Joint of the Foal

Objective To (1) develop an arthroscopic approach to the subextensorius recess of the lateral femorotibial (LFT) joint in foals and (2) report its use in foals with LFT joint sepsis. Study Design (1) Anatomic study and (2) retrospective case series. Sample Population (1) Cadaveric hind limbs (n = 32 foals) to delineate the anatomy of the subextensorius recess; 13 foal limbs for cadaver surgery to assess the approach to the subextensorius recess; and (2) foals (n = 8) with LFT joint sepsis. Methods (1) The LFT joint was distended and examined ultrasonographically. Dissection was used to document periarticular landmarks, potential distal arthroscopic portals, and assess iatrogenic damage after cadaveric surgery. (2) Retrieval of data from 8 foals with LFT joint sepsis treated using the arthroscopic approach. Results (1) The optimal arthroscopic approach to the distal subextensorius recess is craniolaterally, 8–10 cm distal to the tibial plateau, immediately caudal to the peroneus tertius muscle, through the long digital extensor muscle belly, entering the distal extent of the subextensorius recess. Thirteen limbs dissected after cadaver surgery had no iatrogenic damage to the peroneus tertius muscle or peroneal nerve. (2) Two foals were euthanized. Resolution of sepsis occurred in 6 foals, and all were sound at follow‐up >9 months after surgery. Conclusion The subextensorius recess may be safely accessed arthroscopically in foals.