The clinch knee, often called the long knee or straight knee from the plum, is one of Muay Thai's defining techniques. It is delivered from inside the clinch, the close-range grappling position unique to the sport, where two fighters fight for control of the head, neck, and arms. The clinch knee operates at the shortest range in striking, almost zero distance, and is scored highly because it requires both control of the opponent's posture and a powerful upward drive of the entire body. A steady stream of clinch knees can break ribs, knock the wind out of an opponent, and decide rounds even when no other strike is landing.
Mechanically, the clinch knee starts with the grip. The most common is the Thai plum, where the kicker laces both hands behind the opponent's head with the elbows pressed tightly together in front of the opponent's collarbones. The grip controls the head, and where the head goes the body follows. To throw the knee, the kicker pulls the opponent's head down and slightly to one side while driving the opposite hip upward. The kneecap travels in a straight line into the rib cage or sternum, while the support foot pivots and the heel often rises off the floor at impact.
Power comes from the hip and from the opponent's own bodyweight. The pull on the head meets the rise of the knee, doubling the force of impact. The support leg drives upward like a piston, the core contracts, and the toes of the kneeing leg point downward to extend the strike. Posture inside the clinch matters enormously. The kicker keeps their own head up and elbows tight, denying the opponent leverage to break the grip.
Tactically, the clinch knee is essential against opponents who close distance to escape kicks, against pressure fighters who try to back the kicker onto the ropes, and against any opponent whose conditioning is suspect. Common entries include catching a kick and stepping into the clinch, parrying a punch and ducking into the body, or simply walking the opponent into a corner. Strong clinch fighters can dominate entire rounds by tying up and kneeing, scoring heavily even when their opponent throws more strikes outside.
Common errors include gripping the head with the hands far apart, which lets the opponent posture up and break the plum; squaring the hips so the knee travels forward rather than upward; standing flat-footed on the support leg, which kills the upward drive; and neglecting to pull the head down to meet the knee.
Variations include the side knee, which curves across into the floating ribs; the diagonal knee, which targets the sternum; and the jumping knee, which adds airborne body weight at the cost of balance. Counters include posturing up to break the grip, swimming the arms inside the opponent's elbows to take the plum back, or using a body lock to negate the knee entirely.
The clinch knee is associated with Dieselnoi Chor Thanasukarn, whose six-foot-two frame and brutal clinch game made him untouchable in the early 1980s, and with Petchboonchu FA Group, a multiple-time stadium champion whose knee work in the clinch is considered a textbook example. In the modern era, Nong-O Hama and Panpayak Jitmuangnon continue the tradition of fighters whose clinch knees decide fights.