Diagnosis

Impaired mobility arises from a number of conditions, each with unique treatment approaches. Mobility impairment should be defined in comparison to an individual ani­mal's baseline, which is generally before injury and often at its optimum immediately after the end of growth and development.

1) A reduction in the amount of time an animal can ambulate. An example would include paresis secondary to interver­tebral disc disease.

2) A change in the quality or character of movement, e.g. animals with proprioceptive deficits, muscle strains, or compensatory weight shifting secondary to osteoarthritis.

3) An inability to rise from a lying or seated position. Osteoarthritis and interverte­bral disc disease may require short- or long-term assistance, through the use of direct manipulation, slings, and special harnesses.

4) Painful movement. Pain should be consid­ered impaired mobility even when visual changes in locomotion are not present. Chronic muscle or articular pathology may, in early stages, produce discomfort without obvious gait abnormalities.

The diagnostic approach for disorders of movement should be methodical and com­prehensive. Animals with relatively clear primary diagnoses may have secondary or compensatory changes that promote or induce other injuries. The vast majority of mobility changes will have a neurologic or musculoskeletal origin, and as such, the history and physical examination should be comprehensive and include an assessment of neurologic function, soft tissue pain, joint function, and orthopedic integrity.

Chronic Disease Managementfor Small Animals, First Edition. Edited by W. Dunbar Gram, Rowan J. Milner and Remo Lobetti.

© 2018 John Wiley & Sons, Inc. Published 2018 by John Wiley & Sons, Inc.

History and Physical Examination

Owners should be asked to describe the ways in which their pet's mobility has changed and whether there was an acute inciting incident or if it developed slowly without a definitive origin.

Special consideration should be given to cats, which as a species may be less overt with clinical signs of mobility disorders. Screening questions can include whether the cat is still able to jump to the same height, whether they continue to be found in similar areas throughout a house rather or if they are more sedentary in a particular area. A gen­eral assessment of activity can be solicited from the owner - if such information cannot be provided, an accelerometer may be used to monitor activity and to compare to pub­lished averages. A period of weight gain in the absence of dietary change may indirectly suggest reduced voluntary activity.

A comprehensive rehabilitation exam ben­efits all dogs with changes in their ability to ambulate. This examination should include the elements in the following subsections.

Comprehensive Physical Examination with a Systems Approach

Aging animals in particular may present with concurrent medical conditions. An ophthalmic examination allows for screening for changes that may impact vision, assessment of the integument may provide information about nutritional status and the presence of any chronic dermatoses, assessment of dentition allows for the recognition of conditions caus­ing oral pain, cardiothoracic abnormalities may reveal disorders expected to reduce stamina (heart disease, chronic bronchitis), abdominal palpation could reveal concurrent neoplasia or gastrointestinal disorders, body condition should be assessed given the obvi­ous impacts of adiposity on joint and spinal loading, and the urogenital system externally examined as dogs with impaired mobility are predisposed to urinary tract infections and perineal dermatitis.

Neurologic Examination

Animals are frequently misdiagnosed with orthopedic issues when the primary pathology is neurological and vice versa. Consequently, an abbreviated neurological examination can quickly and simply screen for common neu­rogenic causes on a differential diagnosis list.

The neurologic examination should mini­mally include the following:

1) Assessment of a patient's affect and behavior. Altered mentation and behav­iors are suggestive of forebrain disease. Aging animals should be evaluated for cognitive dysfunction.

2) Assessment of critical cranial nerves which could influence mobility. This includes menace detection (cranial nerves II and VII), pupillary light reflex (II, III), palpebral reflex (V, VII), assess­ment of facial symmetry (VII), and a gag reflex (IX, X). Any head tilt should be closely evaluated for central or peripheral vestibular causes.

3) An evaluation of an animal's stance can suggest different neurologic lesions. A wide-based stance is characteristic of proprioceptive ataxia, a narrow stance may be due to paresis, and decreased weight bearing could be either pain or root signature.

4) Proprioception should be evaluated in all patients. This should be done with ade­quate support of an animal because allowing a pet to bear weight on the dorsal surface of its paw may test sensory rather than proprioceptive fibers. Proprioceptive fibers, located primarily in the outer tracts of the spinal cord are often first affected by many compressive myelopa­thies. Hopping and wheel-barrowing pro­vide additional tests of proprioception.

5) Withdrawal reflexes should also be assessed in all patients. A weak or absent withdrawal reflex is suggestive of a disor­der affecting either the peripheral nerves (neuropathy) or a central lesion within the area of the reflex arc (C6-T2 for fore­limbs, L4-S2 in the hindlimbs).

6) Additional reflexes may be tested to further localize pathology. These are described in greater detail elsewhere, but it is important to note that the forelimb reflexes are less reliable in normal patients than are those of the hindlimb.

7) Examination of anal tone is advised in all older animals with impaired mobility. A rectal examination, apart from being a component of a comprehensive physical examination, can provide assessment of the lumbosacral space, disorders of which may be characterized by pain, neurologic deficits, and/or abnormal micturition or defecation.

Orthopedic Examination

The orthopedic examination should be sys­tematic in order to best evaluate potential pathology. A system whereby the examiner moves from head to tail, and from ventral to dorsal, appears to enhance the ability to detect lesions. This procedure can be done as follows:

1) Cervical range of motion should be eval­uated. Both neurologic (intervertebral disc disease, cervical spondylomyelopathy) and orthopedic diseases (arthritis) may cause resistance to range of motion.

2) The forelimb should be evaluated by start­ing with the digits and moving proximally. Digital osteoarthritis and sesamoiditis are frequently overlooked as a source of mobility impairment. The carpus should be evaluated for laxity as well as crepitus. The elbow should be evaluated in exten­sion and the presence of any effusion determined. Long bones should be pal­pated, especially in large breed dogs at risk of osteosarcoma. The shoulder joint is supported by soft tissues and as such the range of motion in the shoulder should be evaluated in all directions. Retired canine athletes may be at increased risk of medial shoulder instability, characterized by an increased abduction angle. Delayed cranial reach ofthe shoulder may be due to infraspi­natus pain and contracture. The biceps should be evaluated for tenosynovitis - the area of the bicipital bursa and the insertion should both be evaluated. The scapula itself should be moveable based on its muscular attachment. Reduced flexion of any joint may be suggestive of osteoarthritis.

3) The thoracolumbar spine should be eval­uated for pain from the spinal column or from the surrounding epaxial muscula­ture. The presence of kyphosis may sug­gest underlying pain in this area, and both kyphosis and lordosis may result in altered carriage of the limbs and changes in stride length and quality.

4) The hindlimb is evaluated in a similar fashion as the forelimb, with digits and sesamoids being evaluated first. The tar­sus should be examined for reduced range of motion. Long bones should be pal­pated, especially the proximal tibia and distal femur in large dogs. Stifle range of motion should be assessed and compared to the contralateral side. Medial buttress should be assessed. The thickness of the patellar tendon should be palpated, and the presence of effusion caudal to this tendon noted. Cranial drawer and tibial thrust testing should be completed, and drawer should be evaluated in flexion to assess for chronic partial tears. The hip can be examined dynamically by placing a hand over the hip during gaiting and pas­sively by an assessment of extension.

5) Pelvic symmetry should be evaluated and lumbosacral and tail palpation performed.

Soft Tissue Assessment

The examination of soft tissue and fascia is commonly overlooked in a patient with mobility impairment. However, some soft tissue pathology may be the primary source of pain or alterations in gait, and most ani­mals with chronic orthopedic or neurologic pain will display secondary discomfort, spasm, or strain in adjacent soft tissue struc­tures. A skilled soft tissue assessment takes a commitment to the assessment of various muscles and ligaments in normal patients on routine physical examination. Careful moni­toring of a patient's demeanor or behavior during muscle manipulation can provide feedback on potential discomfort in a certain area. The following represents a list of major muscle groups that warrant examination.

1) Brachiocephalicus: This muscle of the neck can become a source of discomfort due to strain from forelimb lameness, contralateral hindlimb lameness, or pri­mary cervical pathology.

2) Infraspinatus and supraspinatus: These muscles may produce primary shoulder pathology and instability when injured, but may also be a source of discomfort with forelimb pathology or in overweight animals.

3) Triceps: The triceps should be evaluated in animals with elbow pathology. The long head of the triceps appears particu­larly predisposed to sensitivity.

4) Epaxial muscles: Sensitivity in the epaxial muscles can be both a primary and sec­ondary finding. Concurrent evaluation of the patient's neurologic status is critical.

5) Iliopsoas: The combined psoas major and iliacus muscles are a common cause of mobility impairment in canine athletes but may also be a secondary source of pain in animals with hip or stifle disor­ders. The muscle can be assessed by lat­eral palpation of the lumbar vertebrae and by palpation of the muscle when the hindlimb is extended and internally rotated. Abduction may also trigger dis­comfort when the coxofemoral joint is extended.

6) Sartorius: This muscle lies cranially to the quadriceps and is frequently sore and contracted in patients with cranial cruciate insufficiency or coxofemoral disease.

7) Pectineus: The pectineus functions as an adductor of the hindlimb and is located on the medial surface of the proximal hindlimb coursing from the iliopubic eminence to the femur. The muscle is a frequent cause of discomfort in animals affected by hip dysplasia and/or arthritis.

8) Calcaneal tendon complex: Stifle flexors joining the calcaneal tendon are predis­posed to injury with significant load bear­ing. More commonly, however, pain may cause persistent activation of the muscles including the gracilis, biceps femoris, and semitendinosus.

Differential Diagnoses

A comprehensive physical examination per­mits broad categorization of a patient's symptoms and allows the practitioner to bet­ter localize the anatomic site of mobility impairment if not apparent during visual gait assessment.

Neurologic findings should prompt consid­eration of a select group of common differen­tial diagnoses, and mobility impairment will most commonly be a result of pathology in the spinal column. Spinal dysfunction may generally be graded using five categories:

1) Spinal pain only

2) Ambulatory paresis

3) Nonambulatory paresis

4) Plegia with pain sensation

5) Plegia without deep pain sensation

Intervertebral disc disease is the most commonly encountered chronic neurologic impairment affecting mobility. Large breed dogs will typically present with chronic lesions of lower severity and some present exclusively with proprioceptive deficits. Conversely, Dachshunds and other chondro- dystrophic breeds may present with either chronic or acute disc protrusions. Many such dogs have other sites of disc protrusion, and therefore may require chronic management even after acute decompressive surgery.

Congenital malformations should be con­sidered in young animals with ataxia or other neurologic signs. Large breed dogs with cervical spondylomyelopathy may respond well to integrative treatments when signs are mild to moderate. Small-breed dogs with caudal occipital malformation and other congenital malformations respond variably to integrative interventions.

Acute vascular events and trauma to the spine may cause significant and sudden presentation of neurologic symptoms. Fibrocartilaginous embolism is a frequent cause of asymmetrical hindlimb plegia which generally has an excellent rate of recovery. Similarly, noncompressive traumatic lesions to the spinal column typically result in lesion improvement. However, both may cause chronic mobility impairment when recovery is incomplete.

Neoplastic lesions may present as progres­sive chronic conditions, and the presence of asymetrical muscle mass with a root signa­ture in an older dog should prompt this differential diagnosis.

Osteoarthritis is the most common cause of impaired mobility in animals, and more than half of all small animals living to life expectancy will have evidence of the condi­tion. Radiographic diagnosis is generally definitive, but the presence of reduced range of motion and significant crepitus are strong indicators of this chronic inflammatory con­dition. Young animals with developmental orthopedic disease, especially of the elbows, often present with early-onset arthritis which can significantly impact an animal's lifelong comfort level and in some cases may result in euthanasia before life expectancy is reached. Osteoarthritis can affect any joint, including the articular facets. Degenerative joint dis­ease should be distinguished from traumatic arthritis, infectious arthritis, and immune- mediated polyarthropathies. In areas where rickettsial diseases are common, screening should be performed.

Developmental orthopedic diseases includ­ing hip dysplasia and elbow dysplasia (char­acterized by ununited anconeal process, fragmented medial coronoid process, osteo­chondrosis dissecans, and/or elbow incon­gruity) are important causes of lameness in young animals and predispose to degenera­tive joint disease. Early prophylactic integra­tive interventions may reduce the onset of clinical signs. Gait abnormalities are fre­quently observed by the owners, and exami­nation may reveal the presence of incongruity, pain, and effusion.

Active dogs and performance animals may present with chronic orthopedic injuries resultant from a single episode of trauma. These include digital fractures, especially in racing Greyhounds, carpal or tarsal chip fractures, or avulsion injuries. Radiographs or computed tomography, when available, are generally adequate to distinguish degen­erative joint disease from chronic conditions amendable to surgical intervention.

Older dogs should be carefully evaluated for early neoplastic lesions causing mild lameness or subtle changes in mobility. Osteosarcoma, for example, has been iden­tified due to the presence of increased tem­perature over the distal radius of a Great Dane during a rehabilitative examination for hindlimb lameness. Such examples illus­trate the importance of a comprehensive examination.

Soft tissue pathology may be identified in either an orthopedic examination or in a dedicated soft tissue assessment. The characterization of such lesions remains controversial. The human literature refers to myofascial trigger points as hyperirritable areas within a taut band of muscle. The molecular mechanisms of such phenomena are unclear, however, it is thought that such palpable areas represent non-neurologic acti­vation of muscle fibers which then induce sec­ondary inhibition of the muscle and weakness. These areas are characterized by an aversive response on palpation, and are frequently addressed with local manipulative therapies.

Muscle strains are more commonly recog­nized by practitioners than trigger points and typically result from eccentric loading, that is stretching of a muscle during activation. The established grading system in veterinary medicine is as follows:

Grade 1: mild: myositis and bruising but min­imal disruption of architecture

Grade 2: moderate: myositis and partial tear­ing of fascia and/or muscle

Grade 3: severe: tearing of the fascial sheath, disruption of fibers, hematoma

Muscles responsible for significant loading, such as the biceps, gracilis, iliopsoas are most commonly affected. The grading system is of less utility for chronic lesions. Chronic repet­itive strain results in a combination of Stage 1-like inflammation and local trigger points with secondary muscle inactivation.

Chronic tendonitis occurs in several areas in the dog, and is most common in active ani­mals or those with previous surgical inter­vention. Patellar tendonitis, for example, is a possible complication of osteotomies for cruciate ligament insufficiencies. Biceps ten­osynovitis with or without calcification is encountered in some dogs. Other areas of potential tendonitis are less common; for example, the tendon of the abductor pollicus longus (dewclaw) may be subject to repeti­tive strain. Tendon strains are described sim­ilarly as to those affecting muscle:

Grade I: minor stretching or tearing

Grade II: partial tear with functional pre­servation

Grade III: near complete or complete tear with secondary instability and functional compromise.

Sprains describe acute ligamentous injury, and are therefore separate from strains. If severe, surgical intervention is typically required to restore stability.

Infectious and neoplastic causes of myositis are far less common than primary pathology resultant from repetitive strain or acute eccentric loading. The practitioner must carefully assess examination findings to determine whether soft tissue pathology is primary or compensatory to another inciting cause, such as osteoarthritis or paresis.

Diagnostic Challenges

Endocrine disorders may affect muscle, tendons, ligaments, and peripheral nerves. For example, hypothyroidism in some cases induces a peripheral neuropathy in dogs and selective atrophy of muscle fibers. Hyperthyroidism is associated with general weakness in cats with­out definitive histologic lesions. Hyperadren- ocorticism induces changes in muscle condition, such as necrosis and atrophy of faster twitch muscle fibers, as well as in fibro­blast maturation.

Metabolic disorders and electrolyte distur­bances cause weakness, fatigue, and other symptoms which must be separated from primary causes of impaired mobility. Patients with potassium abnormalities, diabetes, hypertension, and others must be examined in the context of the patient's entire medical history and symptoms. When metabolic con­ditions are identified, concurrent manage­ment is indicated.

Mobility declines with age and caretakers may be financially unprepared or unwilling to invest in the cost of diagnostic evaluations for suspected non-surgical lesions. Such owners should be counseled on the general disadvantages of empiric treatment. However, many treatment modalities can be elected without specific knowledge of the precise lesion localization because of systemic treatment effects. Radiographs are likely the most accessible and cost-effective of tests for orthopedic localization. Other considerations include computed tomogra­phy (CT), with its advantage of being multi­dimensional and more time and cost effective for the assessment of multiple joints. CT rarely provides adequate resolution for neu­rologic lesions, except in the case of a miner­alized disc protrusion. Alternatives include MRI, at a significant owner investment, or for muscle and tendon injuries, diagnostic ultrasound. The latter requires a linear high frequency probe and a trained operator.

Novel Diagnostics

A variety of new diagnostic resources are available. Gait analysis is increasingly com­mon in rehabilitative practice and allows for generation of patient-specific data on the rel­ative weight distribution between limbs. The advantage over force plates are that entire gait cycle parameters can be analyzed instead of simply one leg at a time. Standing force ana­lyzers may provide information about inac­tive weight distribution, but similar information may be obtained from looking carefully at the amount of central pad contact in a dog's comfortable standing position. Kinematic data uses analysis of video footage to determine joint angles during motion. Similar work has been done using walking fluoroscopy. Thermal cameras are available that purportedly detect cutaneous tempera­tures, elevations of which may be suggestive of tissue inflammation. These technologies are typically reserved for those cases in which a definitive localization cannot be made dur­ing the comprehensive evaluation or are reserved for confirmation of clinical suspi­cions. Overreliance on technology in the diagnosis risks missing pathology which may be identified on a thorough examination.

Comorbidities

Obesity must be prioritized in any patient with impaired mobility, and the concurrent management of obesity is discussed later. Obesity results in increased mechanical load­ing in patients with impaired mobility. The hor­monal effects of adiposity, such as on adipokine balance, may actually worsen osteoarthritis and other conditions by causing a chronic inflam­matory state. Dogs fed to maintain lean body mass have a lower risk of arthritis, and when arthritis does occur, a reduced severity of clini­cal signs. Moreover, overweight dogs live an estimated two fewer years than lean dogs.

The presence of any other systemic disease may increase a patient's fatigue and decrease adaptability to impaired mobility. Consequently, animals should receive a comprehensive health screen before treatment of mobility is initiated.

Prognosis

Most chronic mobility disorders are incura­ble. Surgical interventions may improve an acute deterioration in the case of interverte­bral disc disease or severe hip dysplasia. More commonly, however, patients develop impairment of other joints, other discs, or have progression of non-surgical osteoar­thritis. The goals of most interventions are to preserve existing function, to maintain or improve muscle mass, to maintain existing neurologic function, and to provide general comfort through a multimodal approach.

A New Integrative Approach

Normal functional mobility relies on a complex synergy between multiple body systems and tissues. The approaches designed to preserve such function should be equally multimodal. A multifaceted approach of weight management, drug therapy, nutritional management, dietary supplements, surgery, and exercise has long been advocated for osteoarthritis. A similar individualized patient approach should be elected for all mobility disorders and can be divided into the following categories:

1) Controlled exercise: Exercise should be low-impact, high-resistance in order to preserve muscle mass without overloading joints. Hydrotherapy may be especially helpful for severe cases of altered ambulation.

2) Pain control: A combination of therapeutic modalities should be used to address pain. These may include acupuncture, pharma­ceutical drugs, nutraceuticals, soft tissue therapies, and photobiomodulation.

3) Nutrition: Nutritional requirements change as an animal's condition or diag­nosis changes. A dog with significant paresis and intolerance to exercise may require caloric reduction. However, the amount of protein per calories should be elevated to maintain lean body mass.

4) Tissue stimulation: Endogenous repara­tive process may be engaged with a variety of modalities, such as platelet therapies, shockwave, acupuncture, electrostimula­tion, stem cells, and others. The suitability of such modalities is tissue- and condition­dependent. Treatment of issues following secondary compensation is critical.

5) Weight management: Obesity must be avoided in all animals with compromised mobility.