I just reviewed an MRI and x-rays of a patient with chronic sesamoid injury and there definitely was plantar plate involvement. This is a great article documenting an unstable plantar plate with a 2mm forward position of the non injured sesamoids. The x-rays should be taken in a position where the big toe is bent upwards, called a stress x-ray.
Arrow under the big toe joint shows a disrupted plantar ligament (plantar plate) with intense inflammation.
