Albert Barnes Commentary Psalms 38:7

"For my loins are filled with burning; And there is no soundness in my flesh." — Psalms 38:7 (ASV)

For my bones are filled with a loathsome disease - This would seem to indicate the seat of the disease, though not its nature. The word used here, according to Gesenius (Lexicon), properly denotes the internal muscles of the loins near the kidneys, to which the fat adheres. The word rendered “loathsome”—the word “disease” being supplied by our translators—is derived from קלה qâlâh—a word which means to roast, to parch, as fruit, grain, etc.; and then, in the form used here, it means scorched, burned, which in turn signifies a burning or inflammation; and the whole phrase would thus be synonymous with “an inflammation of the kidneys.” The word used here does not imply that there was any eruption or ulcer, though it would seem from (Psalms 38:5) that this was the fact, and that the inflammation had produced this effect.

And there is no soundness in my flesh - See (Psalms 38:3). His disease was so deep-seated and so pervading, that there did not seem to be any soundness in his flesh. His whole body seemed to be diseased.