An anterior interval release is a surgical procedure to remove scar tissue in the 'anterior interval' - a region behind the patellar tendon.
In patients with arthrofibrosis, the anterior interval behind the patellar tendon may become obliterated with adhesions and scar tissue, and the tissues may stick down to the front of the tibia, together with the tendon.
Anterior interval release removes the scar tissue in the anterior interval, and frees up the tendon again, allowing an improved range of motion and reducing patellar pain.
Surgery for such scarring is specialist domain, and this procedure should only be carried out by a surgeon experienced in this problem. The release is generally performed via the arthroscope.
Surgical Technique for Release of Anterior Interval Scarring of the Knee After Anterior Cruciate Ligament Reconstruction. Rose M, McNeilan R, Genuario J and Schlegel T. Arthroscopy Techniques September 2018 Volume 7, Issue 9, Pages e887–e891.
Intraarticular arthrofibrosis of the knee alters patellofemoral contact biomechanics. Mikula JD, Slette EL, Dahl KD, Montgomery SR, Dornan GJ, O’Brien L, Turnbull TL and Hackett TR. J Exp Orthop. 2017 Dec; 4: 40.