JILL K. LUTHER, DVM 1 , CRISTI R. COOK, DVM, MS, Diplomate ACVR 1 , and JAMES L. COOK, DVM, PhD, Diplomate ACVS 1 1 Comparative Orthopaedic Laboratory, University of Missouri, Columbia, MO Vet Surg June 2009 38 4 520-529 Objective—To evaluate after 12 weeks the effects of caudal medial meniscal release (MR) in the cranial cruciate ligament-intact canine stifle. Study Design—Blinded, prospective in vivo study. Animals—Purpose-bred hound dogs (n=10). Methods—Either MR (n=5) or a sham (SH) surgery (n=5) was performed via arthroscopy. Orthopedic examination and subjective lameness evaluation were performed in each dog preoperatively and at 4, 8, and 12 weeks after surgery. Twelve weeks postoperatively, ultrasonographic, radiographic, and arthroscopic examinations were performed on the operated stifles. Gross pathology of the articular cartilage, cruciate ligaments, and menisci was assessed. India ink staining of the femoral and tibial articular surfaces was performed to determine the percent area of articular cartilage damage. Results—At 8 and 12 weeks after surgery, MR dogs were lamer than SH dogs. At 12 weeks, the degree of radiographic OA was significantly higher in MR stifles than in SH stifles. Gross and sonographic meniscal pathology was more severe in MR stifles compared with SH stifles. MR stifles had significantly more severe articular cartilage pathology compared with SH stifles 12 weeks after surgery; pathology was most severe in the medial compartment. Conclusions—MR alone is associated with articular cartilage loss, further meniscal pathology, degenerative joint disease, and lameness. Clinical Relevance—Subsequent osteoarthritis and dysfunction of the stifle joint should be considered when making clinical decisions regarding MR in dogs.