お膝元	91140	89.2%
お膝下	691	0.7%
お膝許	24	0.0%
御膝元	1093	1.1%
御膝下	85	0.1%
御膝許	0	0.0%
おひざ元	9137	8.9%

@@ -8,0 +9 @@
+<ke_inf>&rK;</ke_inf>
@@ -11,0 +13 @@
+<ke_inf>&rK;</ke_inf>
@@ -14,0 +17 @@
+<ke_inf>&sK;</ke_inf>
@@ -17,0 +21 @@
+<ke_inf>&sK;</ke_inf>
@@ -20,0 +25 @@
+<ke_inf>&sK;</ke_inf>
@@ -23,0 +29 @@
+<ke_inf>&sK;</ke_inf>

In daijr/s, the senses don't overlap. Koj, however, has a "宮城または幕府などの在る地" sense on its ひざもと entry, and GG5 has a "権力者の居住地" sense that redirects to お膝元.
So sense 4 on our ひざもと entry roughly corresponds to sense 2 here. I don't know if we want to align them.

Shouldn't this be more closely alignes to 
ひざもと？ (or the other way around)

gg5
daijs (sense 3): "権力者の直接の支配下。「家元の―で起こった不祥事」"
meikyo (sense 3): "権力者の支配が直接およぶ所。「財務省の─で起こった収賄事件」"

Splitting into senses.

@@ -30,5 +30,16 @@
-<xref type="see" seq="1721910">膝元・ひざもと・4</xref>
-<gloss>home territory of a powerful figure</gloss>
-<gloss>Imperial Court</gloss>
-<gloss>businessman's turf</gloss>
-<gloss>Shogun's headquarters</gloss>
+<gloss>beside a nobleman</gloss>
+<gloss>close aid (of a nobleman, etc.)</gloss>
+</sense>
+<sense>
+<pos>&n;</pos>
+<gloss>place where a high ranking person resides</gloss>
+<gloss>one's own city (of a shogun, lord, etc.)</gloss>
+<gloss>Imperial capital</gloss>
+<gloss>Imperial court</gloss>
+<gloss>(shogun's) headquarters</gloss>
+</sense>
+<sense>
+<pos>&n;</pos>
+<gloss>place under one's direct control</gloss>
+<gloss>one's own turf</gloss>
+<gloss>one's own backyard</gloss>