The owner of a Horsham health club has admitted cheating several insurance companies in a phony billing scheme. 50-year-old Doctor Joseph Lerner of Chalfont pleaded guilty to health care fraud and mail fraud in federal court in Philadelphia.  He is a chiropractor who owns the Horsham 24-Hour Fitness and Wellness Center on Witmer Road.  Federal prosecutors say he billed Blue Cross, Aetna and other insurers, claiming he had given club members treatments that were medically necessary.  But in reality they got massages and personal training, which the insurance companies do not cover.  He billed them for about $3 million, and they paid nearly $2 million on his fraudulent claims.