ACL Reconstruction Step by Step: Patellar Tendon (BTB) Graft
Medically reviewed by M. Brett Raynor, M.D., board-certified orthopaedic sports medicine surgeon. Updated October 2026.
This animation walks through how I reconstruct a torn ACL with a patellar tendon graft, also called a bone-patellar tendon-bone (BTB) graft. Once it tears, the ACL typically does not heal on its own, so instead of repairing it I make a new one. After checking the knee under anesthesia, I look inside through two small poke-hole incisions and clear out the torn ligament. The new ligament comes from the middle third of your own patellar tendon, with a block of bone at each end so the graft heals bone to bone. I make a socket in the thigh bone and a tunnel in the shin bone right where your ACL attached, pull the graft into place, and hold it with a screw at each end. Bone saved from the tunnel fills the spots where the graft was taken.
In this video
- 0:00 The ACL and how it tears
- 0:23 Checking the knee under anesthesia
- 0:40 Small incisions and a look inside
- 1:04 Clearing out the torn ACL
- 1:16 Taking the patellar tendon graft
- 1:45 Making the socket in the thigh bone
- 1:56 Making the tunnel in the shin bone
- 2:10 Pulling the new ligament into place
- 2:26 Bone grafting and the new ACL
- 2:45 Closing the incisions
Common questions
Why does a torn ACL need to be reconstructed?
Once it tears, the ACL typically does not heal on its own. Instead of sewing it back together, I make a new ligament and place it right where the old one was.
Where does the new ACL come from with a patellar tendon graft?
From the middle third of your own patellar tendon, the tendon just below the kneecap. A double-bladed knife cuts a strip exactly 10 millimeters wide, and a small saw frees a block of bone at each end so the graft heals bone to bone.
How is the new ligament held in place?
A screw that dissolves over time holds the graft in the thigh bone. I bend the knee back and forth to settle the graft, straighten it, and lock the bottom end with a second screw.
What happens to the spots where the graft was taken?
The special reamer I use for the shin bone tunnel saves that bone, and I use it to fill the spots in the kneecap and shin bone where the graft came from.
How are the incisions closed?
Each small poke hole is closed with a single stitch. The graft incision is closed with dissolving stitches under the skin and skin glue on top.
Full transcript
This is the knee. The anterior cruciate ligament, or ACL, runs through the middle of the joint and keeps the tibia, or shin bone, from sliding and twisting out from under the femur, or thigh bone. Once it tears, the ACL typically does not heal on its own. During surgery, once you're asleep, I check the knee one more time. This shifting is called a pivot shift, and is exactly what we're here to fix. It's what you feel when you do cutting, pivoting and twisting sports that makes your knee feel unstable. I start with two small poke-hole incisions, one on each side of the patellar tendon in the front of the knee. One is for the camera and the other is for my instruments. First I look at everything inside the knee: the meniscus, the cartilage, and the other ligaments. A small motorized shaver clears out the torn ACL, and this is what I see through the camera. Then I clear out the other end, up on the thigh bone. For the graft, I make an incision over the patellar tendon and go down through the layers to the tendon. Your new ligament comes from the middle third of your own patellar tendon. A double-bladed knife cuts a strip exactly 10 millimeters wide. A small saw frees a bone block at each end, so the graft heals bone to bone. The graft comes out in one piece. While my assistant prepares the graft, I close the tendon that's left behind. A guide lets me place a flexible pin right in the center of where your ACL started. A flexible reamer makes a socket in the thigh bone that's exactly the size of your graft. Then I place a pin in the shin bone so it comes out right where the ACL attached. This special reamer saves the bone from the tunnel, and I'll use that later to bone graft the defects in the patella and tibia. Now the new ligament is pulled up into place. A screw that dissolves over time holds the graft in the thigh bone. I bend the knee back and forth to settle the graft, straighten it, and lock the bottom end with a second screw. The bone I saved from the tunnel fills the spots where I took the graft. Now the knee is stable, and it bends and straightens all the way. Inside, the new ligament sits right where the old one was. Each small poke hole is closed with a single stitch. The graft incision is closed with dissolving stitches under the skin and skin glue on top.
Related
This video and page are general education and are not a substitute for an evaluation of your own knee, shoulder or hip.