A sensor for detecting infiltration at a catheter infusion site may include a first elongate sensor member couplable to a first location proximate the catheter infusion site, and a second elongate sensor member couplable to a second location proximate the catheter infusion site. The first elongate sensor member may include a first marking and the second elongate sensor member may include a second marking. The first elongate sensor member may slidably couple with and translate relative to the second elongate sensor. The first and second markings may indicate a range of relative positions between the first and second elongate sensor members as the first and second elongate sensor members translate relative to each other. At least one relative position within a range of relative positions between the first and second elongate sensor members may be indicative of infiltration at the catheter infusion site.