Knee Strike

Knee Strike is defined initially on B232 / B404 and It is similar to Kicking (same damage) with reduced reach.
It had three special benefits over a knee making it worth the range reduction:
*no chance of falling on a miss (it wasn't a kick, it wasn't 'otherwise resolved like a kick' like a Back Kick was)
*defence penalties for foes grappled by the kneer. The -2 was presumably in addition to the -4 DX suffered by people grappled in general, although MA had not yet clarified this meant -2 to parry / -2 to block / -1 to dodge.
*no penalty (normally -3) to hit the groin if the foe was grappled from the front (presumably this means any of the 3 front hexes, though some might read that as only the middle-front)
GURPS Martial Arts 76 did not do much to expand things except reference the Grab and Smash rules on MA118. MA90 abbreviates it as Knee.
==Kneeing using DX==
19 June 2009 in an instance of a Krommquote, the response "This is correct." was delivered by Kromm in response to this post by "Perfect Organism" who was later renamed Sam Baughn:
:I'd say you can strike with your knee, but it counts as a Kick rather than a Knee Strike for rules purposes.
:In much the same way that you can define a strike with an elbow to targets you could normally punch as a Punch, but if you want to get the benefits of an Elbow Strike you need to use an appropriate skill.
PO/SB was referring to errata introduced in 
==Damage bonus==
Even though B404 says it does the "same damage" as a kick, common sense would dictate that only kicks delivered with the foot would get the +1 damage (thrust+1 crushing) from wearing boots.
Kicks delivered using the leg, or knee strikes, should logically not get that bonus, and do just thrust+0 crushing.
For comparison, B229 also says "Kicking does +1 damage relative to a punch" but that's obviously relative to a NAKED UNTRAINED (thrust-1 crushing) punch: it would not be relative to a punch with a fist-load (thrust+0) or a punch enjoying a damage bonus from a boxing skill.
Shin Kick on MA112 puts into print such common sense:
:You get +1 damage for rigid leg armor, not for boots.
That would obviously be a sensible guideline for knee strikes as well. The only difference being it would be rigid knee armor and not rigid shin armor that would be needed.
LT100 for example discusses "partial limb armor", dividing "arm" into forearm/elbow/upper arm/shoulder and "leg" into shin/knee/thigh. The 4th joint connecting the leg to the torso hip is already a separate location.
==Hurting Yourself==
B379's "Apply this damage to the body part you used to attack, if you are using hit locations." would logically mean that damage should never be applied to the foot, because knee strikes do not hit with the foot. So logically this should be the leg.
Kicking could plausibly (in basic set) be used with EITHER body part, the foot or the leg.
MA112 brings this up when discussing the Shin Kicks option. 
==See also==
*Elbow Strike
*Shin Kick
Category:Techniques