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Digital Sheath Tenosynovitis in Horses

By

Matthew T. Brokken

, DVM, The Ohio State University

Last full review/revision Sep 2015 | Content last modified Jun 2016

Tenosynovitis of the digital flexor tendon sheath is common in all types of working horses. Chronic digital sheath tenosynovitis may be bilaterally symmetric in the hindlimbs in horses with minimal clinical significance (“windpuffs”). The digital sheath encompasses the superficial and deep digital flexor tendons and extends from the distal one-third of the metacarpus/metatarsus distally to just proximal to the navicular bursa. Asymmetric tendon sheath effusion typically indicates a problem. Lameness degree is variable, depending on the structure(s) involved, and may increase with exercise. Horses are typically sore on firm flexion of the distal limb. Although some cases of tenosynovitis are primary and respond to conservative therapy with or without treatment of the sheath with corticosteroids and/or hyaluronic acid, others are secondary to lesions of structures contained within the sheath. Ultrasonographic examination of the entire digital flexor tendon sheath, including the intersesamoidean ligament and distal sesamoidean ligaments, is recommended and typically leads to a diagnosis. However, marginal tears of the deep digital flexor tendon (typically dorsolateral in the pastern) and tears of the manica flexoria can be difficult to diagnose via ultrasound but are confirmed through tenoscopic examination of the sheath. Verification of site of lameness should be confirmed via intrathecal injection of analgesia.

Palmar/plantar annular ligament constriction can be primary due to desmitis of the ligament or secondary to longstanding tenosynovitis or enlargement of the flexor tendons contained within the fetlock canal. Clinical signs are similar to those of other causes of tenosynovitis and include pain on palpation, swelling, and lameness, especially after forced flexion of the distal limb. Careful ultrasonographic examination is recommended to assess accompanying pathology. Treatment can be either conservative (ie, steroids) or surgical (palmar/plantar annular ligament desmotomy). Surgery is best performed tenoscopically, which allows visualization of the remainder of the sheath for primary pathology and assessment of the degree of constriction.

Other common causes of tendon or ligament pathology distal to the fetlock include desmitis of the distal sesamoidean ligaments (oblique and straight), deep digital flexor tendon, superficial digital flexor tendon, and the distal digital annular ligament. Any of these conditions can result in tenosynovitis of the digital sheath and can typically be diagnosed using ultrasonography or MRI.

OTHER TOPICS IN THIS CHAPTER
Lameness in Horses
Overview of Lameness in Horses
The Lameness Examination in Horses
Imaging Techniques in Equine Lameness
Arthroscopy in Equine Lameness
Regional Anesthesia in Equine Lameness
Disorders of the Foot in Horses
Osseous Cyst-like Lesions in the Distal Phalanx in Horses
Bruised Sole and Corns in Horses
Canker in Horses
Fracture of Navicular Bone in Horses
Fracture of Distal Phalanx in Horses
Keratoma in Horses
Laminitis in Horses
Navicular Disease in Horses
Pedal Osteitis in Horses
Puncture Wounds of the Foot in Horses
Pyramidal Disease in Horses
Quittor in Horses
Quarter Crack in Horses
Scratches in Horses
White Line Disease in Horses
Sheared Heels in Horses
Sidebone in Horses
Thrush in Horses
Disorders of the Pastern and Fetlock
Fractures of the First and Second Phalanx in Horses
Fractures of the Proximal Sesamoid Bones in Horses
Osteoarthritis of the Proximal Interphalangeal Joint in Horses
Palmar/Plantar Metacarpal/Metatarsal Nonadaptive Bone Remodeling in Horses
Sesamoiditis in Horses
Chronic Proliferative Synovitis in Horses
Digital Sheath Tenosynovitis in Horses
Disorders of the Metacarpus in Horses
Tendinitis in Horses
Suspensory Desmitis in Horses
Inferior Check Desmitis in Horses
Bucked Shins in Horses
Exostoses of the Second and Fourth Metacarpal Bones in Horses
Fractures of the Small Metacarpal (Splint) Bones in Horses
Fracture of the Third Metacarpal (Cannon) Bone in Horses
Disorders of the Carpus in Horses
Fracture of the Carpal Bones in Horses
Subchondral Bone Disease of the Third Carpal Bone in Horses
Tearing of the Medial Palmar Intercarpal Ligament in Horses
Osteoarthritis of the Carpus in Horses
Distal Radial Exostosis and Osteochondroma of the Distal Radius in Horses
Carpal Hygroma in Horses
Rupture of the Common Digital Extensor Tendon in Horses
Disorders of the Shoulder in Horses
Developmental Diseases of the Shoulder in Horses
Fractures of the Shoulder in Horses
Bicipital Bursitis in Horses
Infection of the Shoulder in Horses
Suprascapular Neuropathy in Horses
Osteoarthritis of the Shoulder in Horses
Disorders of the Elbow in Horses
Developmental Orthopedic Disease in the Elbow of Horses
Fractures of the Elbow in Horses
Osteoarthritis of the Elbow in Horses
Collateral Ligament Injury in the Elbow of Horses
Disorders of the Metatarsus in Horses
Bucked Shins/Dorsal Cortical Fractures of the Third Metatarsal Bone in Horses
Exostoses of the Metatarsal Bones in Horses
Diaphyseal Fracture of the Third Metatarsal Bone in Horses
Incomplete Longitudinal Fractures of the Plantar Aspect of the Third Metatarsal Bone in Horses
Focal Bone Reaction and Avulsion Fractures of the Third Metatarsal Bone in Horses
Fractures of the Second and Fourth Metatarsal Bones in Horses
Enostosis-like Lesions of the Third Metatarsal Bone in Horses
Disorders of the Tarsus in Horses
Failure of Ossification of the Distal Tarsal Bones in Horses
Osteoarthritis of the Distal Tarsal Joints in Horses
Osteoarthritis of the Talocalcaneal Joint in Horses
Osteoarthritis of the Tarsocrural Joint in Horses
Synovitis/Capsulitis of the Tarsocrural Joint in Horses
Osteochondrosis of the Tarsocrural Joint in Horses
Osteitis of the Calcaneus in Horses
Fractures of the Distal Tarsal Bones in Horses
Fracture of the Talus in Horses
Fracture of the Fibular Tarsal Bone (Calcaneus) in Horses
Fracture of the Lateral Malleolus of the Tibia in Horses
Tarsal Joint Luxation in Horses
Desmitis of the Collateral Ligaments of the Tarsus in Horses
Rupture of the Fibularis (Peroneus) Tertius in Horses
Stringhalt
Curb in Horses
Disorders of the Tarsal Sheath in Horses
False Thoroughpin in Horses
Luxation of the Superficial Digital Flexor Tendon from the Tuber Calcanei in Horses
Gastrocnemius Tendinitis in Horses
Calcaneal Bursitis in Horses
Capped Hock
Disorders of the Stifle in Horses
Osteochondrosis of the Stifle in Horses
Subchondral Cystic Lesions in Horses
Meniscus and Meniscal Ligament Injuries in Horses
Cranial and Caudal Cruciate Ligament Injuries in Horses
Collateral Ligament Injuries in Horses
Intermittent Upward Fixation of the Patella and Delayed Patella Release in Horses
Fragmentation of the Patella in Horses
Patellar Luxation in Horses
Patellar Ligament Injuries in Horses
Gonitis and Osteoarthritis in Horses
Chondromalacia of the Femoral Condyles in Horses
Fractures of the Stifle in Horses
Disorders of the Hip in Horses
Luxation of the Coxofemoral Joint in Horses
Pelvic Fracture in Horses
Osteoarthritis and other Coxofemoral Joint Diseases in Horses
Disorders of the Back and Pelvis in Horses
Spinal Processes and Associated Ligaments in Horses
Articular Process−Synovial Intervertebral Articulation Complexes in Horses
Vertebral Bodies and Discs in Horses
Muscle Strain and Soreness in Horses
Lumbosacral Junction Abnormalities in Horses
Sacroiliac Joint Abnormalities in Horses
Developmental Orthopedic Disease in Horses
Osteochondrosis in Horses
Physitis in Horses
Flexural Deformities in Horses
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In all animals, the motor unit of skeletal muscle consists of the motor neuron, the neuromuscular junction, and muscle fibers. Muscle dysfunction—such as ataxia, paresis, or paralysis—most commonly originates in which of the following locations?
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