2. The mucous bursa of the extensor tendon of the long pastern (lateral extensor) is somewhat smaller, and lies, likewise, beneath the tendon, between it and the capsular ligament of the fetlock-joint ([Fig. 17, h]).
3. The mucous bursa of the navicular region lies between the under surface (gliding surface) of the navicular bone and the flexor pedis perforans tendon (deep flexor). Its width equals the length of the navicular bone, and it extends upward and downward beyond the bone. Above, it is separated from the sheath of the perforans tendon (“great sesamoid sheath”) by a membranous partition; below, it passes to the attachment of the perforans tendon to the semilunar crest of the os pedis.
(b) There is but one tendon sheath in the foot—the sheath common to the two flexor tendons (great sesamoid sheath). It encloses the flexor tendons from the middle third of the cannon down to the middle of the short pastern, and is intimately united with the flexor pedis perforans tendon ([Fig. 17, f, f′, f″, f‴]. [Fig. 18, d, d′, d″, d‴]).
Fig. 17.
Right forefoot seen from the external side; f, f′, f″, f‴, great sesamoid sheath (tendon sheath); g, mucous bursa beneath anterior extensor tendon of the toe; h, mucous bursa beneath extensor tendon of long pastern; i, synovial distension of the fetlock-joint; 7, suspensory ligament; 9, cannon bone; 10, outer sesamoid bone; 12, fetlock-joint; 13, lateral cartilage; 14, suspensory ligament of the lateral cartilage. (Ellenberger in Leisering’s Atlas and Veterinary Anatomy, Sisson, Saunders.)
Fig. 18.
Right forefoot seen from the inner side; d, d′, d″, d‴, great sesamoid sheath; e, mucous bursa beneath anterior extensor tendon of the toe; f, synovial distension of fetlock-joint; 10, inner sesamoid bone; 11, “x” ligament; 14, fetlock-joint; 15, lateral cartilage; 16, suspensory ligament of lateral cartilage (Ellenberger in Leisering’s Atlas and Veterinary Anatomy, Sisson, Saunders.)
Altering the Relative Tension of the Flexor Tendons
and Suspensory Ligament of the Fetlock-Joint.