With many of these increasingly popular sports, there is no specific breed requirement or physical examination by a veterinarian. A major concern for veterinarians is that little research has been conducted to determine the effect of these sports on the dogs.
Injuries can be sustained to a variety of tissues, including bone (fractures), ligament and tendon (tears), the cardiovascular system (dehydration and heat stress), skin (lacerations), and many others. Types of injuries vary according to the sport a dog engages in (see Which injuries are most common in various sports?). In this article, I'll describe common injuries in sporting dogs. And in the next article, I'll discuss how to prevent these injuries.
FOOT PAD INJURIES
Foot pad lacerations and nail trauma are common in sporting dogs. Most of these injuries are treated by the owners themselves, but full-thickness foot pad lacerations through the dermis need surgical closure if the dog is to return to athletics.4 The suture material should be large enough to withstand weight-bearing, and the interrupted mattress suture pattern is best to prevent tearing out of the sutures.4 In addition, a heavily padded splint bandage may be applied during the healing period to reduce weight-bearing and shear stress on the sutures.
Puncture wounds on the palmar or plantar surface of the paw can be problematic since a dog can develop deep digital flexor tendonitis, a potentially career-ending problem. Systemic antibiotics are recommended as well as surgical management with débridement and suturing of the puncture.4 Broad-spectrum antibiotics should be administered while culture and sensitivity test results (culture obtained during débridement procedure) are pending, and then therapy should be based on both aerobic and anaerobic culture results.
Some the most common injuries in sporting dogs involve the shoulder. This is especially true in agility dogs.5 Common shoulder problems include biceps brachii tenosynovitis, supraspinatus insertionopathy, infraspinatus contracture and bursal ossification, teres minor myopathy, and medial shoulder instability (medial glenohumeral ligament sprain, subscapularis tendinopathy, and joint capsule laxity).
Other forelimb injuries in sporting dogs, which have been described elsewhere, include shoulder trauma, elbow injuries, and carpal injuries. Shoulder trauma can result in fracture, osteoarthritis, or luxation. Injuries to the elbow encountered in canine athletes frequently include luxation, medial and lateral collateral ligament rupture, congenital or traumatic fragmented medial coronoid process, or osteoarthritis of unknown cause.4
Biceps brachii tenosynovitis
The biceps brachii originates on the supraglenoid tubercle; passes across the shoulder joint, down the humerus in the intertubercular groove; and inserts on the proximal medial ulna and the proximal cranial radius. Its function is to flex and supinate the elbow, extend the shoulder, and passively stabilize the shoulder in neutral and flexed positions.6,7 Biceps brachii tenosynovitis is usually a chronic injury of the forelimb that develops over time as the tendon tears slowly and then subsequently develops dystrophic mineralization.8 On orthopedic examination, pain will be elicited on palpation of the tendon and flexion of the shoulder joint. In some cases, conservative management will resolve the problem, and some veterinarians recommend rest with one injection of corticosteroids into the shoulder joint, which is confluent with the tendon bursa; however, to my knowledge, no definitive published reports have shown efficacy of corticosteroid injections for biceps tendonitis.8
Rehabilitation, without surgery, often includes therapeutic ultrasound, passive range of motion exercises, strengthening exercises, and underwater treadmill therapy.9
The prognosis is good to excellent for most dogs treated surgically with either technique, but their level of performance in athletics after surgery has not been scientifically evaluated.8,10,12 Further research in injured sporting dogs after their performance in athletic competition is needed to determine how well these dogs regain their function as athletes.
The decision to treat should be based on a dog's clinical presentation since mineralization of the tendon can be present and identified as an incidental finding on radiographs without any clinical signs of lameness or pain on palpation. Treatment can be aimed at surgical removal of the ossified body, but the condition can recur, and, in one report, three of 16 dogs (19%) had a poor surgical outcome.14 Extracorporeal shock wave therapy, laser therapy, and therapeutic ultrasound have been reported as treatments for the condition, along with underwater treadmill therapy and exercises to restore shoulder function and resolve pain associated with the condition, but prospective placebo-controlled trials have not been reported.9,15,16 In horses, various tendon injuries have been treated successfully with platelet-rich plasma and stem cells; this method of stimulating repair of a strained tendon is currently under investigation in dogs.17-20 For athletes that do not respond to rehabilitation, surgery is recommended to resect the torn or mineralized portion of the tendon.14
Infraspinatus contracture and bursal ossification
The infraspinatus muscle arises from the infraspinatus fossa of the scapula, crosses the shoulder joint, and inserts on the humerus at the greater tubercle just distal to the supraspinatus insertion point.6 This muscle has many functions for the shoulder—flexion and extension, passive stability, and lateral rotation of the forelimb.6 Labrador retrievers and other breeds may develop tendon and bursal ossification of the infraspinatus muscle.9,21 One of the first reports of mineralization of the infraspinatus tendon was in Labrador retrievers; progressive lameness was reported to develop in this breed.21,22 Affected dogs may show no clinical signs, or pain may be present on palpation of the tendon craniolaterally on the shoulder joint, and the dogs may exhibit progressive lameness.21 Diagnostic ultrasound may be used to visualize the damaged tendon and to monitor healing after treatment.23
Some dogs respond to conservative management with rest and corticosteroid injection into the bursa or tendon, while others require surgical resection and release of the tendon. As many as 50% may not fully recover from the condition.21 During arthroscopy, pathology is often noted in other shoulder structures such as the medial glenohumeral ligament or biceps brachii tendon, and these problems may contribute to the patient's lameness and dysfunction.24 The prognosis for return to previous levels of athletic ability in animals with this condition alone is unknown since it frequently occurs with other shoulder pathologies.
Teres minor myopathy
The teres minor muscle flexes the shoulder joint and can slightly rotate the forelimb medially. It arises from the infraglenoid tubercle of the scapula and crosses the shoulder to insert on the lateral diaphysis of the humerus.25 Teres minor myopathy results in a consistent lameness with pain on extension of the shoulder.25 When tissue and muscle just caudal to the acromial process are palpated, sometimes a firm band of tissue and shoulder pain are evident. This condition can be diagnosed by ultrasonographic examination of the tendon and muscle. Conservative management may only be effective early in the course of the disease. If the condition is chronic, surgery is needed to resect the fibrous tissue and tendon.25
Medial shoulder instability
Numerous treatment methods have been reported, including conservative management with hobbles and cage rest, thermal capsulorrhaphy, prosthetic medial ligament repair, biceps brachii tendon transposition, and subscapularis tendon imbrication.27,32-34 Conservative management has been reported to have a good to excellent outcome in 25% of dogs, whereas surgical treatment has improved outcomes, with 85% to 93% of dogs attaining good or better function.27,32 However, after surgery, some dogs may have continued lameness.27,32,34 Rehabilitation may improve the function and performance of some dogs after recovery from surgery. In severe cases of instability, arthrodesis may be performed, but the dog cannot continue to compete at the same level as before the injury.32
In the carpus, sporting dogs can incur flexor carpi ulnaris tendinopathy or avulsion, superficial digital flexor tendon elongation (flyball and agility dogs), medial and lateral collateral ligament rupture, abductor pollicis longus tenosynovitis (earthdogs), palmar ligament hyperextension injury (flyball and dock dogs), radial carpal bone luxation or fracture, styloid process fracture and joint instability, or carpal osteoarthritis (racing greyhounds).4,25,35-37
Tendinopathy and even avulsion of the insertion of the flexor carpi ulnaris from the accessory carpal bone can occur in sporting dogs, especially those working on uneven terrain and hard surfaces. In dogs, the injury presents with what looks like hyperextension of the carpus and is differentiated from tears of the flexor retinaculum by palpating distal to the accessory carpal bone (which should palpate normally if the flexor carpi ulnaris is strained or avulsed). If the flexor retinaculum is torn, the dog will stand with the affected limb hyperextended, and there will be swelling or enlargement of the soft tissues on the palmar aspect of the carpus distal to the accessory carpal bone.38
Treatment consists of surgical repair of the avulsion by using a three-loop pulley suture technique (usually with a bone tunnel created in the accessory carpal bone), splinting for three weeks, and then rehabilitation for a gradual return to function.38 Treatment of strains or tendinopathies can be conservative with laser or shockwave therapy used to stimulate healing of the insertion and increase the strength of the healed fibers.39-41 During therapy and for three weeks after treatment, the dog should be maintained in a splint or orthotic brace to support the healing structures.
In the hindlimb, hip dysplasia and osteoarthritis of the hip, stifle, and tarsus are not uncommon and usually a consequence of preexisting developmental orthopedic disease.42 Sporting dogs can also develop gracilis-semitendinosus myopathy and contracture, iliopsoas muscle trauma leading to femoral neuropathy, cruciate ligament rupture, patellar tendonitis, long digital extensor tendonitis due to proximal luxation, and gastrocnemius head or popliteal muscle avulsion injury.24,36,43,44 Chronic injuries of the hindlimb include Achilles tendon rupture, iliopsoas myopathy, partial cruciate ligament rupture, and lumbosacral disease.5,45,46
Below are specifics on identifying and treating iliopsoas muscle injury, popliteal muscle avulsion, gastrocnemius muscle avulsion, superficial digital flexor tendon luxation, and Achilles tendon injury—conditions many practitioners may not be as familiar with.
Iliopsoas muscle injury
The psoas major muscle arises from the transverse processes of the second and third lumbar vertebrae and the ventral vertebral bodies of the fourth through seventh lumbar; it then joins with the iliacus muscle (which arises from the ilium) to become the iliopsoas muscle that inserts on the lesser trochanter of the femur.6 The femoral nerve passes through the muscle fibers of the psoas and iliopsoas muscles, and with hemorrhage in this area or tearing of the muscle, compression and stretching of the nerve from the hematoma may cause a femoral neuropathy.44,47,48
Injury to the iliopsoas muscle is not as uncommon as once thought.49 Dogs that are infrequently active and overextend themselves can experience this injury as well as athletes. Affected dogs may not be lame but may show signs of decreased performance, difficulty rising, and a shortened stiff gait in the hindlimbs.50 In severe cases, they may have signs of femoral nerve paralysis. A sprain of the muscle will be mildly painful on palpation, but when there has been hemorrhage into the muscle fibers, severe pain can be present because of compression and inflammation of the closely related femoral nerve.47
The injury can be diagnosed on ultrasonographic examination.49 Treatment of mild cases often involves therapeutic ultrasonography, passive range of motion exercises, and a gradual return to activity.49 If this therapy fails, surgical resection of the iliopsoas tendon of insertion can resolve the clinical signs.47
Popliteal muscle avulsion
The popliteal muscle flexes the stifle and internally rotates the tibia in relation to the femur. It originates on the lateral femoral condyle with its sesamoid near its origin, crosses the stifle joint caudally, and then inserts on the proximal medial tibia.6
When avulsion occurs, it is at the lateral femoral condyle, and pain will be present on extension of the stifle as well as when the caudal aspect of the stifle is palpated.51 On radiographs, the popliteal sesamoid at the caudal aspect of the stifle joint will be displaced distally. Surgery to reattach the muscle to the lateral femoral condyle is recommended, but as with gastrocnemius avulsion (see below), return to peak performance is unlikely.4
Gastrocnemius muscle avulsion
The gastrocnemius muscle originates in two heads, one on each supracondylar tuberosity, and each contains one sesamoid, called a fabella. The muscle tendon inserts on the calcaneal bone to extend the tarsus and flex the stifle.6
Avulsion of the gastrocnemius muscle at its head results in an acute nonweightbearing lameness, while partial avulsion in which some of the origin of the muscle remains attached to the femur results in partial weightbearing. The hock may be hyperflexed in some dogs when they try to bear weight on the limb because the gastrocnemius muscle functions to flex the stifle.52,53 On radiographs of the stifle, one or both of the fabellae may be distally displaced.
Conservative management of partial avulsions with therapeutic ultrasound and rest can resolve clinical signs of lameness in some dogs.54 Surgical reattachment of the muscle head to the supracondylar femur and restriction of stifle extension for three weeks postoperatively are recommended in athletes. The lameness will resolve, but dogs rarely return to their previous performance level.24
Superficial digital flexor tendon luxation
Collies and Shetland sheepdogs are becoming increasingly popular in flyball and agility sports and are more prone to lateral luxation of the superficial digital flexor tendon than are other breeds.55 The superficial digital flexor arises from the lateral supracondylar tuberosity of the femur and the lateral fabella, crosses the stifle joint and lies proximally cranial to the gastrocnemius, and then passes medially to the caudal aspect of the gastrocnemius tendon as it courses distally. The superficial digital flexor tendon continues distally after inserting on the tuber calcanei to insert on the proximal caudal border of the second phalange.6
The luxation occurs at the level of the calcaneal bone where the retinaculum ruptures. The dog will exhibit pain and lameness in the hindlimb and may have its toes elevated off the floor when standing on the affected limb. The diagnosis is made by palpation of the area where the tendon can be replaced and luxated again, similar to a luxating patella.55
Treatment involves surgical repair of the retinaculum by suturing it over the tendon by using simple interrupted or cruciate sutures with absorbable monofilament suture material. The tendon itself is not sutured so that it may continue to glide over the calcaneal bone and function to flex the digits and extend the tarsus. After surgical repair, rehabilitation and a gradual return to activity are recommended.4
Achilles tendon injury
The Achilles tendon, also called the common calcaneal tendon, is composed of three tendinous structures including the gastrocnemius tendon, the superficial digital flexor tendon, and the common tendon of the biceps femoris, gracilis, and semitendinosus muscles. This tendon is most frequently injured by laceration in both dogs and cats.56 Chronic and acute injuries of the Achilles tendon may occur. Acute injuries are most commonly due to lacerations and often occur within 48 hours before presentation. Subacute injuries have occurred at any time between two and 21 days, and chronic injuries are older than 21 days.57
Subacute and chronic injury pathogenesis and diagnosis. The pathogenesis of subacute or chronic injuries not associated with laceration of the tendon is not well understood. Progressive rupture of the Achilles tendon can develop over time, with injury most commonly to the gastrocnemius component affected.56 Suspected initiators of such chronic ruptures have included chronic corticosteroid ingestion and fluoroquinolone (even one dose in people may cause tendon damage) administration.58,59 Most veterinary cases are in large-breed, active dogs and may be related to chronic repetitive injury during exercise.57
Tendon repair augmentation. Augmentation of the primary repair is controversial. Acute lacerations or injuries of less than 48 hours' duration usually are not augmented. Subacute or chronic lacerations are most often augmented with various implants or tissues intended to remain permanently at the repair site.61,63 Biological implants include free fascia lata graft, porcine small intestinal submucosa, or the semitendinosus muscle.66 Injection of the tendon repair with concentrated platelet gel has been advocated to speed healing postoperatively, but, to my knowledge, no controlled studies have proven its effectiveness in tendon healing in dogs.67 Porcine small intestinal submucosa has been used experimentally in dogs and facilitates complete tendon healing within 90 days of the surgically created Achilles tendon defect.68
Postoperative care and return to function. Protection of the repair early in the healing process is a must. Additional support can be from a cast, external skeletal fixator, splint, or calcaneal-tibial bone screw. All of these methods provide relief of tension on the repair for three weeks to three months after surgery.56,69 Many practices support the repaired tendon with an orthotic such as a neoprene brace, hinged splint, or other custom-made device so that the dog may again begin training as soon as possible.
Immobilization for longer than four weeks will result in deleterious effects on the joints, some of which can be permanent.70 In addition, early mobilization of the joint improves the healing process and augments the tensile strength of the tendon repair.67,71,72 The average length of time that some form of immobilization is needed is about 10 weeks, but most surgeons decrease the amount of support incrementally over that time. A dog may achieve a stable functional hindlimb after repair, but return to competition is less likely than return to function as a pet. A study from New Zealand determined that only seven of 10 dogs returned to full or substantial levels of work after healing, and 29% of those had moderate persistent lameness.46
New methods to enhance and speed healing of tendon repairs are being investigated. Low energy shock wave therapy may enhance neovascularization of the bone-tendon junction in dogs.73 Ultrasound therapy may be able to accelerate healing and tendon maturation in dogs as well.74 While no clinical studies exist, future developments and methods of postoperative care may improve the functional outcome in small animals with Achilles tendon injuries.
This review describes a wide range of causes of lameness in sporting dogs, but many new conditions will be identified as the popularity of dog sports continues to increase. A thorough physical examination and an investigation of intermittent lameness in sports dogs early in the course of their disease can prolong their athletic careers and may even improve performance. Diagnosis of these conditions should involve any appropriate combination of radiography, ultrasonography, nuclear scintigraphy, computed tomography, MRI, and arthroscopy, among other diagnostic tools. Further research is needed to determine the best treatment options for these dogs, but new developments continue to be investigated.
Of course, preventing injury in these canine athletes is the primary goal of owners, trainers, and veterinarians. See the related article "Preventing injury in sporting dogs" for measures you can recommend clients take to help their dogs stay healthy and injury-free as they participate in sports.
Wendy Baltzer, DVM, PhD, DACVS
Department of Clinical Sciences
College of Veterinary Medicine
Oregon State University
Corvallis, OR 97331
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