Inflammation of the proximal aspect of the interosseus medius muscle, or suspensory ligament (i.e., proximal suspensory desmitis, PSD) of the hind limb, is a common cause of acute or chronic lameness of horses and is most commonly diagnosed in competition horses 4 to 10 years old.

Until recently, there was little scientific basis for interpreting response to various techniques of diagnostic analgesia of the digit.