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Flexural Deformities in Horses

(Contracted tendons, Club foot, Knuckling)

By

Chris Whitton

, BVSc, FANZCVS, PhD, Equine Centre, University of Melbourne

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

Flexor tendon disorders are associated with postural and foot changes, lameness, and debility. They may be congenital and therefore identified in newborn foals or acquired at an older age. Uterine malposition, teratogenic insults (arthrogryposis), and genetic defects have been either implicated or proved to cause contracted limbs in newborn foals. Chronic pain is the most common cause of acquired tendon contracture. Pain can arise from physitis, osteochondrosis, degenerative joint disease, pedal bone fracture, or soft-tissue wounds and infection. Pain induces reflex muscle contraction with shortening of the flexor musculotendinous units. The horse walks on its toes or knuckles in the fetlocks or occasionally the pastern joint. Nutritional errors referable to problems associated with bone growth (ie, osteochondrosis and physitis) are intimately associated with the syndrome and must be addressed as part of treatment. (See also Contracted Flexor Tendons Contracted Flexor Tendons Ruptured common digital flexor tendon as a sequela of contracted flexor tendons in a foal. Contracted flexor tendons are probably the most prevalent abnormality of the musculoskeletal system... read more Contracted Flexor Tendons and see Angular Limb Deformities Angular Limb Deformities In angular limb deformities, which are congenital or acquired skeletal defects, the distal portion of a limb deviates laterally or medially early in neonatal life. In utero malposition, hypothyroidism... read more Angular Limb Deformities .)

Clinical Findings:

Signs vary widely in newborn foals. Some cannot stand, some attempt to walk on the dorsum of their fetlocks, and others can stand but knuckle in the fetlocks or carpi. One foal may improve spontaneously, yet another, seemingly healthy at birth, may become progressively worse. In older foals, onset tends to be rapid; such animals may walk around on their toes with their heels off the ground. A slower onset is characterized by an upright hoof with an elongated heel and concave toe. Physitis frequently is evident in these horses. Involvement of both forelimbs is common, with a tendency to be worse in one leg. Toe abscesses are a frequent complication of the hoof and locomotion changes, and they add to the pain and deformity.

Older horses (1–2 yr old) commonly knuckle in the metacarpophalangeal joints. Yearlings usually are more severely affected and more difficult to treat than younger animals. It is important to attempt to identify any underlying bone or joint disease, but this is often difficult and may have resolved.

Treatment:

Mild cases in newborn foals often require no treatment. More severe cases require supportive therapy, and it is essential to correct failure of passive transfer of immunity if the foal has not been able to nurse adequately. Use of splints necessitates careful fitting and management, because rubbing sores are common and can be severe. Casts are generally safer if used only for short periods (5–7 days). High-dose oxytetracycline therapy is commonly used (40–60 mg/kg).

Early acquired cases in older foals and weanlings can be managed conservatively with nutritional correction, proper hoof trimming, and analgesia; however, once the deformity is present for >1 wk, this is rarely successful. Surgical treatment can be simple or complex, depending on the degree of involvement. Desmotomy of the accessory ligament of the deep digital flexor tendon (inferior check desmotomy) is the most successful and commonly used procedure for flexural deformity of the distal limb and does not interfere with future performance. Superior check ligament desmotomy may be included for horses with fetlock deformities. For carpal deformities, sectioning of the tendons of insertion onto the ulnaris lateralis and flexor carpi ulnaris is performed. In hindlimbs, tenotomy of the medial head of the deep digital flexor is performed, because the inferior check ligament is often vestigial. In severe cases, tenotomy of the deep digital flexor tendon can be used as a salvage procedure. Nutritional correction, proper foot trimming, and analgesia are integral to recovery when surgery is performed. The prognosis is fair to good for horses diagnosed early and managed properly.

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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