Last updated: May 25, 2026
Quick Definition
A diagonal knee is a Muay Thai-derived strike where a fighter drives the knee upward and across the body at an angle, landing on an opponent’s ribs or flanks. In MMA, it is most often thrown from the clinch to slip past a defending guard.
What is a diagonal knee?
The diagonal knee, known in Thai as Khao Chiang, is one of the core knee techniques of Muay Thai and a regular sight in MMA whenever fighters tie up in the clinch. The strike travels along an upward and inward angle rather than straight forward, which is the feature that separates it from the more familiar straight knee. According to Evolve Vacation, the technique lands “diagonally up and inwards” and targets the ribs or latissimus dorsi muscle on either side of the body.
In the context of mixed martial arts, the diagonal knee fits into a wider family of knee strikes that fighters import from Muay Thai. The Art of Eight Limbs gives Muay Thai practitioners (and the MMA fighters who train in it) eight points of contact, with knees being one of the most damaging at close range. The diagonal version exists because a straight knee, useful as it is, gets blocked easily when an opponent guards the centerline of the midsection. A knee that arrives on a slanted path can sneak around that guard and find the softer tissue along the sides of the body.
How the diagonal knee works
The mechanics are closer to a roundhouse kick than to a piston-style straight knee. Muay Thailand describes the technique as similar to a straight knee but with the hips engaged, “as with a roundhouse kick and the knee thrown inwards and upwards.” Power comes from the rotation of the hips and shoulders, not just from a forward thrust.
The typical target sits along the side of the torso. According to Ubud Muay Thai, the diagonal knee lands on the ribs or flanks and bypasses the arms or elbows that would normally guard a centerline strike. A clean shot to that area can damage the ribs, the external obliques, or the latissimus dorsi, and a flush strike to the liver region can end a fight outright.
Range is flexible. The diagonal knee can be thrown from close to mid-range, in or out of the clinch, although most MMA fighters land it from inside the Thai clinch (the plum) when they have a grip on the opponent’s head or neck.
Diagonal knee vs straight knee
Most people land on a glossary page for the diagonal knee because they have heard it mentioned alongside the straight knee and want to know what makes the two different. The table below summarizes the practical distinctions.
| Feature | Diagonal Knee (Khao Chiang) | Straight Knee (Khao Trong) |
|---|---|---|
| Trajectory | Upward and inward at an angle | Straight up and forward |
| Primary target | Ribs, flanks, latissimus, liver region | Sternum, solar plexus, stomach, head |
| Power source | Hip rotation, similar to a roundhouse kick | Forward thrust from the hips |
| Range | Close to mid-range | Close to mid-range |
| Best used when | Opponent’s centerline is guarded | Opponent’s head is pulled down or guard is open down the middle |
| Thai name | Khao Chiang | Khao Trong |
The straight knee is usually the first knee a Muay Thai or MMA student learns because it is the most direct. The diagonal knee comes in as a follow-up tool once the opponent starts defending the middle.
Other knee strikes in the same family
Diagonal knees are one of several Muay Thai knee variations that show up in MMA. A reader who recognises Khao Chiang will probably encounter the others in commentary.
| Strike | Thai name | Brief description |
|---|---|---|
| Straight knee | Khao Trong | Driven forward up the centerline, usually to the sternum or head |
| Curved knee | Khao Khong | A short, hooking knee thrown in tight clinch range |
| Horizontal knee | Khao Tat | Travels parallel to the floor, targeting the side of the body |
| Long knee | Khao Yao | A charging knee thrown from longer range with forward momentum |
| Flying knee | Khao Loi | A leaping knee aimed at the head, usually at a disoriented opponent |
The Muay Thai canon traditionally lists eight knee techniques in total, including smaller clinch strikes like Khao Noi and Khao Kratai, although only a handful see regular use in MMA cage fights.
Are diagonal knees legal in MMA?
Yes, the diagonal knee is a legal strike in mixed martial arts under the Unified Rules of MMA, which govern the UFC, PFL, and most North American promotions. There is no restriction on the angle of a knee; the restrictions concern who can be hit and where.
Knees to the head of a grounded opponent are not allowed under the Unified Rules. Until late 2024, a fighter counted as “grounded” if any body part other than the soles of the feet touched the mat, including a single palm. In July 2024, the Association of Boxing Commissions and Combative Sports voted to change that definition. According to CBS Sports, a fighter must now have a body part other than the hands (a knee, shin, or buttocks) touching the canvas to be considered grounded. The rule debuted at UFC Edmonton on November 2, 2024.
For the diagonal knee specifically, the rule change matters because Khao Chiang is often thrown inside the clinch when one fighter is trying to break grips or change posture. Under the old rule, a fighter could neutralize knees to the head by quickly placing a hand on the canvas. Under the revised rule, that defensive option no longer applies. ONE Championship, which uses a different ruleset, permits knees to the head of grounded opponents and so allows broader use of clinch-and-knee sequences.
Frequently Asked Questions
What does Khao Chiang mean?
Khao Chiang is the Thai name for the diagonal knee strike. “Khao” means knee, and “Chiang” refers to the angled trajectory of the strike.
Is a diagonal knee the same as a roundhouse knee?
The two terms are sometimes used interchangeably. The diagonal knee uses hip rotation similar to a roundhouse kick, which is why some coaches call it a roundhouse knee. The traditional Thai name is Khao Chiang.
Can a diagonal knee be thrown outside the clinch?
Yes. Although it is most associated with the clinch, the diagonal knee can be thrown at close to mid-range without a grip, particularly as a counter when the opponent leans in or steps forward.
How is the diagonal knee different from the horizontal knee?
The diagonal knee travels at an upward angle, roughly 45 degrees. The horizontal knee (Khao Tat) travels almost parallel to the floor and tends to land flatter along the side of the body.
Do MMA fighters score points for diagonal knees?
Yes. Knee strikes in MMA are scored as part of significant striking. A clean diagonal knee to the body in the clinch is typically counted as a power shot under the criteria used by judges.
Sources
- Evolve Vacation. “The Different Types Of Knees In Muay Thai.” Accessed May 2026.
- Evolve University. “The Ultimate Guide To Muay Thai Knees.” Accessed May 2026.
- MMA Underground. “The 8 main knees of Muay Thai.” Accessed May 2026.
- Ubud Muay Thai. “Mastering Muay Thai Knee Techniques and Variations.” Accessed May 2026.
- Muay Thailand. “Muay Thai Knees.” Accessed May 2026.
- CBS Sports. “Commission removes 12-6 elbows from Unified MMA rules, updates grounded opponent rule.” July 2024.
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