The Knee Slice from Half Guard is one of the most fundamental and high-percentage guard passes in Brazilian Jiu-Jitsu. This technique exploits the half guard player’s commitment to the inside position by creating a powerful angle that drives your knee across their legs while establishing dominant upper body control. The pass works by combining forward pressure with lateral movement, using your knee as a wedge to separate the opponent’s legs while your hips drive through the opening.
What makes this pass particularly effective is its ability to shut down the bottom player’s primary defensive tools - the underhook and the inside space. By controlling the crossface and establishing a strong underhook yourself, you neutralize their framing attempts while simultaneously flattening them to the mat. The knee slice motion creates a dilemma: if they focus on stopping your knee, they lose upper body control; if they fight your crossface, your knee slides through uncontested.
This pass represents a cornerstone of modern guard passing systems because it works equally well in gi and no-gi, against all body types, and connects seamlessly to other passing options. When executed with proper timing and pressure, the knee slice becomes nearly unstoppable, forcing the opponent into increasingly desperate defensive reactions that open them up to back takes, mount transitions, or submission attacks.
From Position: Half Guard (Top)
Key Attacking Principles
- Establish crossface control before initiating the pass to eliminate defensive frames
- Drive your knee at a 45-degree angle across the legs rather than straight through
- Keep your hips heavy and close to the opponent throughout the pass
- Use your underhook to lift and flatten the opponent’s torso
- Maintain forward pressure while stepping the trapped leg back
- Control the far side hip to prevent re-guard attempts
- Transition smoothly to side control consolidation immediately after passing
Prerequisites
- Top position in opponent’s half guard with your leg trapped
- Strong crossface established with your shoulder driving into their jaw
- Underhook secured on the far side under their armpit
- Opponent’s bottom shoulder pinned to the mat
- Your weight distributed forward onto their upper body
- Inside knee positioned near their hip line ready to slice
- Base hand posted on the mat for stability and pressure
Execution Steps
- Establish crossface control: Drive your shoulder across the opponent’s face and into their far shoulder, using your forearm to create pressure on their jaw. This control point is critical - without it, they can create frames and prevent your pass. Your weight should be forward, making it difficult for them to turn into you or establish an underhook.
- Secure the underhook: Thread your free arm under their far armpit, gripping around their back or their far lat muscle. This underhook serves multiple purposes: it lifts their shoulder off the mat, prevents them from turning away, and gives you control over their torso rotation. Pull their upper body toward you while maintaining the crossface pressure.
- Flatten the opponent: Using your underhook and crossface together, drive the opponent flat onto their back. Their bottom shoulder should be pinned to the mat, eliminating their ability to come up on their side. This flattening motion removes most of their defensive power and makes the leg extraction significantly easier.
- Position the slicing knee: Place your inside knee (the one on the same side as their half guard grip) directly on their inner thigh or hip crease. Your shin should be angled approximately 45 degrees relative to their body, pointing toward their far hip. This angle is crucial - too straight and you’ll get stuck, too wide and you’ll lose pressure.
- Step back and drive the knee: Step your trapped foot backward while simultaneously driving your slicing knee across their legs toward their far hip. The motion should feel like you’re cutting through their guard with your shin bone as the blade. Keep your hips low and heavy, maintaining downward pressure throughout the movement. Your knee should slide across the top of their thigh, separating their legs.
- Clear the legs and establish side control: As your knee completes the slice and clears their bottom leg, immediately bring your trailing leg through to establish side control. Your hips should land heavy on their torso, with your crossface still active and your underhook controlling their far side. Transition immediately to side control consolidation, using chest-to-chest pressure and controlling their near hip to prevent re-guard.
Possible Outcomes
| Result | Position | Probability |
|---|---|---|
| Success | Side Control | 75% |
| Failure | Half Guard | 15% |
| Counter | Deep Half Guard | 10% |
Opponent Counters
- Opponent establishes a strong underhook and comes up to their side (Effectiveness: High) - Your Response: Switch to a different passing angle such as the backstep or long step pass. You can also address their underhook by swimming your arm over theirs and re-establishing your underhook, or by transitioning to a kimura grip on their underhooking arm. → Leads to Half Guard
- Opponent frames on your hip and creates distance during the knee slice (Effectiveness: Medium) - Your Response: Tighten your crossface and use your underhook to pull them back toward you, collapsing their frame. Alternatively, redirect to an over-under pass or switch to a knee cut variation if they’re committed to extending. → Leads to Half Guard
- Opponent locks a deep half guard as you attempt to extract your leg (Effectiveness: High) - Your Response: Don’t force the pass. Instead, address the deep half guard position first by establishing a whizzer on their underhook, driving your weight back, and working specific deep half guard passing techniques. Only return to the knee slice once you’ve escaped the deep half entanglement. → Leads to Deep Half Guard
- Opponent grabs your slicing leg and prevents it from clearing (Effectiveness: Medium) - Your Response: Use your grip on their far side to off-balance them away from your trapped leg. You can also switch to a leg weave pass, using your free leg to step over their grip and applying pressure to break their hold. → Leads to Half Guard
- Opponent turns away and attempts to take your back during the pass (Effectiveness: Low) - Your Response: This is often a positive development. Maintain your crossface control, sprawl your hips back, and establish front headlock control. From here, you have strong back take opportunities or can transition to turtle attacks. → Leads to Side Control
Test Your Knowledge
Q1: Why is establishing the crossface before attempting the knee slice critical to the pass’s success? A: The crossface eliminates the opponent’s ability to turn into you and create defensive frames. It pins their bottom shoulder to the mat, flattening their posture and removing their strongest defensive position. Without the crossface, they can easily use their arms to create space, block your knee, or recover guard. The crossface also controls their head, which controls their entire body’s orientation.
Q2: What is the correct angle for the slicing knee, and why does this angle matter? A: The knee should slice at approximately 45 degrees toward the opponent’s far hip, not straight across their body. This angle matters because it creates the most efficient cutting motion that separates their legs while avoiding getting stuck on their thigh. A straight angle creates too much resistance, while too wide an angle sacrifices pressure and allows them to recover. The diagonal motion also naturally positions you for the side control transition.
Q3: How do you address an opponent who establishes a strong underhook during your knee slice attempt? A: First, recognize that their underhook significantly compromises your pass. You have several options: swim your arm over theirs to re-establish your underhook, grip their underhooking wrist and apply a kimura lock to neutralize the threat, or abandon the knee slice entirely and switch to a different passing angle such as the backstep or long step. Never force the pass against a strong underhook as it leads to scrambles or sweeps.
Q4: What is the optimal timing window to initiate the knee slice motion? A: The optimal window opens when you have achieved three conditions: crossface is locked with shoulder pressure driving their head away, underhook is secured and lifting their far shoulder, and their bottom shoulder is pinned flat to the mat. The slice should begin immediately after flattening them, before they can recompose frames or recover to their side. Waiting too long allows them to reestablish defensive structures.
Q5: Your opponent posts their hand on your hip as you initiate the knee slice - how do you adjust? A: Their hand post creates a frame that prevents forward pressure. Address this by first tightening your crossface to limit their hip mobility, then use your underhook arm to strip their posting hand by cupping their elbow and driving it across their body. Alternatively, drive your hip into their hand while maintaining forward pressure to collapse their frame, or switch to a leg weave variation by stepping your free leg over their framing arm.
Q6: What direction of force should your knee apply during the slice, and how does this differ from simply pressing down? A: The force should be diagonal - driving your knee toward their far hip at approximately 45 degrees while simultaneously applying downward hip pressure. This differs from pressing straight down because pure downward force gets blocked by their thigh and creates a stalemate. The diagonal vector cuts across the grain of their leg, separating their knees apart while your hip weight prevents them from simply rotating to follow your movement. Think of it as slicing across, not pressing through.
Q7: What grip adjustments are required when transitioning from gi to no-gi knee slice? A: In no-gi, you lose collar and sleeve grips that help control distance and posture. Compensate by emphasizing tighter body-to-body contact through your crossface and underhook. Use a gable grip or S-grip behind their back with your underhook arm for better control. Your crossface arm should use forearm pressure rather than collar grip to turn their head. Focus more on chest-to-chest pressure since you cannot use gi friction to maintain position.
Q8: If the knee slice is blocked, what is your primary chain attack? A: The primary chain attack when the knee slice is blocked is the backstep pass or long step pass. When opponent successfully blocks your slicing knee by framing or recovering their knee shield, step your slicing leg back while maintaining upper body control, then immediately circle your free leg around to the opposite side. This creates a new passing angle that exploits their commitment to defending the original line of attack. The kimura grip is also available if they overcommit their underhook during defense.
Q9: How does the opponent’s lockdown defense change your approach to the knee slice? A: When opponent establishes lockdown (figure-four leg entanglement on your trapped leg), the standard knee slice becomes compromised because they control your leg mobility. First, address the lockdown by driving your weight back and pummeling your trapped foot toward their hips to create slack. Use your free leg to post and create base while working to extract your foot. Only return to the knee slice once the lockdown is broken. Alternatively, transition to a whizzer pass or darce choke if they overcommit to the lockdown position.
Q10: What should you do if opponent grabs your slicing leg and prevents it from clearing? A: Don’t fight the grip with pure strength. Instead, use your underhook to off-balance them away from your trapped leg, creating the angle needed to free it. Alternatively, you can switch to a leg weave pass by stepping your free leg over their grip and using downward pressure to break their hold. Another option is to redirect entirely to an over-under pass or different passing angle if their grip is too strong.
Q11: Why is it important to immediately establish side control consolidation after completing the knee slice? A: The moment your legs clear represents your most vulnerable point in the pass. If you don’t immediately secure side control with proper hip pressure and crossface maintenance, the opponent can turn back into you and recover guard. Proper consolidation means landing heavy with chest-to-chest pressure, controlling the far hip to prevent rotation, and maintaining the crossface until you’ve fully stabilized. Many practitioners successfully slice their knee but lose the position by failing to consolidate properly.
Q12: What are the key differences between the knee slice and knee cut passes? A: While both involve driving your knee across opponent’s legs, the knee slice typically originates from half guard with one leg trapped and emphasizes a cutting motion with your shin bone, whereas the knee cut usually starts from open guard with both legs free and involves cutting with your knee itself at a sharper angle. The knee slice focuses more on upper body control and flattening, while the knee cut often emphasizes hip switch and angle creation. They complement each other in passing systems.
Safety Considerations
The knee slice pass is generally safe for both practitioners when performed correctly, but several precautions should be observed. The primary safety concern is avoiding excessive pressure on the opponent’s jaw with the crossface, particularly in training situations. Apply firm control without cranking their neck or driving upward into their jaw, which can cause neck strain or jaw injuries. When slicing your knee across, be mindful not to drive your knee directly into their thigh muscle with excessive force, as this can cause painful bruising or muscle damage. In no-gi situations, ensure your forearm isn’t creating a choke across their throat when establishing the crossface. For the person playing bottom, avoid explosive or jerky movements when defending the pass, as sudden direction changes while your legs are entangled can lead to knee injuries. Both partners should communicate about pressure levels, especially when drilling, and the bottom player should tap if experiencing any sharp pain in their knees or hips during the passing motion.