Most verbs have this characteristic.
"Slouched" is a verb in its past tense or past participle form.
The word huck is a verb. The past tense form is hucked.
The word degrade is a verb. The past tense form is degraded.
"Tethered" is a verb (with present indicative form "tether") in its past tense or past participle form.
The word protruded is a verb. It is the past tense form of the verb protrude.