Post C, Guerrero T, Ohlerth S, Hässig M, Voss K, Montavon PM. Vetsuisse Faculty, University of Zurich, Clinic for Small Animal Surgery, Winterthurerstrasse 260, 8057 Zurich, Switzerland. E-mail: cpost@vetclinics.uzh.ch. VCOT 2008 21 5 440-5 This study describes the appearance of 'joint mice' in the sheath of the deep digital flexor muscle tendon (DDFT) due to osteochondritis dissecans (OCD) lesions in the talocrural joint of 12 dogs. Surgical excision of all free fragments in the DDFT sheath was performed in five dogs, and their clinical progression was documented. The excision of free fragments from the DDFT sheath, but not arthro-tomy, proved clinically beneficial despite the presence of degenerative joint disease. The anatomical communication between the talocrural joint and the DDFT sheath and its dimensions are further illustrated with the use of contrast media and dissection of cadaver limbs.