The plantar plate is a thickened area of the joint capsule of the metatarsophalangeal joints of the foot. Sometimes there is a dysfunction or even a tear of that ligamentous structure. It is reasonable common as far as foot problems go.
The pain of a plantar plate tear is pain under the affects joint on the plantar surface of the foot and usually just distal to the joint. There are a number of clinical tests involving moving the toe can be done by a clinician to help determine if the problem is with the plantar plate or not. There is also a weird feeling that many people describe as a feeling of the sock being scrunched up under the foot, but when the check it is not like that. While the clinical signs of this problem are fairly obvious, and ultrasound is often used to confirm or check the diagnosis.
The cause of a plantar plate dysfunction or tear is typically just overuse. That is that there is too much load placed on the ligament and it becomes inflamed. This overload could be from sports activity, too much walking or being overweight.
Typically a plantar plate tear is initially treated by holing the toe in a plantarflexed position by taping or something like the ToeFix device. A stiffer sole or rocker sole shoe can often help. They tend to not heal on their own, so this treatment approach is often needed for an extended period of time. If that is not successful, then surgery to repair the tear is often indicated.