How to Shoot a Knuckle Ball in Soccer

The knuckleball is one of the trickiest kicking techniques in soccer. However, it is also one of the most difficult to defend. Many of the world’s top soccer stars, including Cristiano Ronaldo, score goals with perfectly executed knuckleballs. 

The knuckleball is effective for the element of surprise it brings. Goalkeepers expect the ball to be kicked directly toward the goal or into a corner. A zigzagging ball is much harder to stop. 

Who Invented the Knuckleball?

The knuckleball technique of kicking a soccer ball originated in the 1950s. Brazillian soccer star Didi invented the kick, originally known as the “folha seca” or “dry leaf.” Now, the kick is called a knuckleball free kick or simply a knuckleball. 

Cristiano Ronaldo and Juninho are known for mastering the knuckleball. Ronaldo’s knuckleball free kick is a goalkeeper’s biggest fear. His name has become so synonymous with this kick that it is now known as the “Cristiano Ronaldo Technique.”

What Is a Knuckleball

The term knuckleball applies to soccer, baseball, and volleyball. It describes a ball kicked, thrown, or served in an unpredictable zigzag trajectory. The knuckleball begins on a straight trajectory and deviates left or right at a distance about the diameter of a soccer ball. The result is a kick that is incredibly difficult to stop, because the defense and goalkeeper don’t know which direction it will soar. 

A knuckleball in soccer has minimal spin. The follow-through is short and controlled to transfer power from the foot to the ball without initiating an unwanted spin. The lack of spin is what creates the zigzag trajectory.

How to Perform the Knuckleball

Every great soccer player wants to master the knuckleball. Learning how to perform this technical style of kicking involves a step-by-step process.

The following video published by Unisport is an excellent tutorial on how to master the knuckleball before taking it to an in-game setting.

The experts at Unisport suggest practicing the knuckleball while the ball is moving because it’s easier. A player can later progress to shooting a still ball. 

Step 1: The Lead-Up

The lead-up to the kick is as important as kicking the ball. The player wants to take three to five steps (like Cristiano Ronaldo) to run up to the ball. They don’t want to approach the ball directly. Instead, the player must run up to the ball at a 35 to 45-degree angle and on their tiptoes. 

Approaching the ball on the toes may feel unnatural at first, but repetition results in muscle memory, and the approach becomes more comfortable over time.

Step 2: Placing the Support Foot

The knuckleball is a challenging kick, so all the elements must combine perfectly for success. The supporting foot should be about 6 to 8 inches from the ball with the toes facing where the player wants the ball to go. 

Step 3: Ensuring Correct Posture

A player must focus on her posture during the run-up, when making contact, and during the follow-through. The body should be straight or leaning slightly forward, never leaning back. 

A straight posture is essential to maintaining control and reducing the spin on the ball. 

Step 4: Making Contact

All the elements of kicking a knuckleball involve limiting the spin as much as possible. The player must strike the ball in the center but slightly toward the lower half. The goal of this point of contact is to reduce spin and keep the ball below the crossbar. Some experts place the ball on the ground with the valve exactly where they want to make contact. This improves accuracy but is only possible when the player can place the ball exactly where he pleases.

The placement of the ball on the foot is just as important. The player aims to strike the ball with the area of the foot between the instep and the center of the ankle joint. This is where the inside part of the foot curves. The ankle remains locked during and after contact. 

Step 5: Following Through

The follow-through with a knuckleball is not as thorough as with many other soccer kicks and shots on goal. The purpose of a short and precise followthrough is to minimize spin while maximizing power.

After making contact, the body will continue in the direction of the strike for a step or two. However, it is critical to limit the forward motion. The kicking foot will continue outward slightly, but the player must try to stop the leg from fully following through. A complete follow-through will result in a ball that flies high and spins. 

Cristiano Ronaldo’s famous knuckleball free kick wasn’t mastered overnight. Many experts state this kicking technique can take up to a year to master. The process of kicking a knuckleball is one that a player must practice again and again. However, once mastered, it is one of the most effective and unpredictable kicking methods for open shots on goal.

The Science Behind a Knuckleball

Understanding the science behind the knuckleball helps players focus on achieving more kicking power with minimal spin.

Caroline Cohen, Ph.D.student at the Ecole Polytechnique’s Hydrodamics Laboratory, studied the physics of the knuckleball and released a report in 2012. She and her colleague studied the trajectories of beads when dropped into a tank of water. All the beads, whether steel or plastic, moved in a zigzag trajectory. 

They discovered that the knuckle effect isn’t due to ball seams or a certain deformation where the foot hits the ball. Instead, the aerodynamic lift forces on a sphere fluctuate when a ball is in flight, creating a zigzag motion. 

The goal is to reduce spin and limit follow-through to let the aerodynamic lift forces do their job. 

Hit the Field

Cristiano Ronaldo makes shooting a knuckleball look easy, but it is the most difficult shooting technique in soccer. The best way to master this effective shot on goal is to practice as often as possible. We suggest players of all ages and skill levels remain patient because a knuckleball takes months or even years to master. 

If you’re interested in other skills to perfect, check out our guide on how to do a Rabona kick.