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Companion animal practice
Investigation of lameness in dogs
  1. Philip Witte and
  2. Harry Scott

2. Hindlimb

Abstract

Hindlimb lameness is seen significantly more frequently than forelimb lameness at the authors' clinic. Lameness in the hindlimb is commonly associated with the stifle (cranial cruciate ligament disease) and the hip (hip dysplasia). Due to the predominance of certain conditions, it is easy to become complacent when diagnosing hindlimb lameness. A thorough investigation must be performed to avoid incorrect diagnosis, even in cases where radiographic signs are suggestive of a specific condition. For example, radiographic signs indicative of osteoarthritis of the hip correlate poorly with clinical signs and should be treated as an incidental finding in the absence of other signs of hip joint pain. This article describes an approach to investigating hindlimb lameness in dogs. An article in the January issue of In Practice (volume 33, pp 20–27) discussed how to investigate lameness in the forelimb.

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Philip Witte graduated from Bristol in 2005. He spent two years working in mixed general practice in Herefordshire followed by six months working with Cape buffaloes in South Africa. He subsequently completed an internship in surgery at Southern Counties Veterinary Specialists, where he is now an orthopaedic resident. He is currently working towards the RCVS certificate in advanced veterinary practice (small animal surgery).

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Harry Scott graduated from Liverpool in 1977. He worked in small animal general practice and completed certificates in dermatology and orthopaedics followed by a fellowship by examination in canine spinal surgery. Since 1999, he has worked in referral practice both in the UK and abroad, and is currently head of orthopaedics at Southern Counties Veterinary Specialists. He holds the RCVS diploma in small animal surgery (orthopaedics) and is an RCVS specialist in small animal surgery (orthopaedics). He has recently become a certified canine rehabilitation practitioner.

Signalment

As discussed in Part 1, signalment can help to formulate a list of differential diagnoses. However, it can also suggest the priority in which particular conditions should be considered in the investigation. For example, in a young small breed dog presented with hindlimb lameness and resentment of hip extension, Legg-Calvé-Perthes disease would be a likely diagnosis, but in a large breed dog of a similar age hip dysplasia may be a more likely cause.

History

As with forelimb lameness, the progression of hindlimb lameness will also influence how the list of differential diagnoses is formulated.

Gait examination

Following a thorough general examination, initial orthopaedic assessment should include observation of the dog's gait and stance (orthopaedic examination of the hindlimb in dogs will be discussed in more detail in an article to be published in the April 2011 issue of In Practice). Dogs with bilateral hindlimb lameness will shift their centre of gravity cranially to transfer weight to the forelimbs by standing with the hindlimbs tucked under the body and arching the back. In severe cases, the degree of kyphosis in dogs with bilateral hindlimb lameness may mimic the appearance of a dog with thoracolumbar spinal pain. Unilateral toe touching lameness is more typical of an acute/subacute injury, such as cranial cruciate ligament rupture and/or meniscal injury. Severe lameness is unlikely to be seen in a dog with more chronic disorders, including osteoarthritis (OA), secondary to hip dysplasia. Dogs with hip dysplasia and mild subluxation may be more comfortable standing with the feet apart in a wide-based stance, while animals with severe subluxation will be more comfortable with the feet placed together in a narrow-based stance. Following initial observation, the dog should also be made to perform some simple manoeuvres in the consulting room such as sit-to-stand and lie-to-stand. Dogs with hip dysplasia and lumbosacral disease will typically have difficulty rising from a sitting or lying position. Dogs with stifle and, to a lesser extent, hock pathology may display a positive ‘sit test’ (see Box 1).

Box 1: Sit test

Dogs with stifle joint pain and, to a lesser extent, hock joint pathology will be unwilling to sit squarely on their haunches with the affected stifle and hock joints fully flexed and will typically either sit in a raised position or adopt a posture whereby they sit on one hip with the affected stifle/hock in a more comfortable extended position.

The purpose of gait analysis is to determine the affected limb and the severity of lameness. Gait analysis is performed at a walk and a trot until the examiner is satisfied that the lame limb has been identified. Initial observation of the patient at a slow walk is preferable because it is easier to evaluate each limb individually. By placing the hands over the dog's hips during walking (Fig 1), it may be possible to palpate the ‘clunking’ that occurs with subluxation and reduction of an unstable dysplastic hip during the stance and swing phases of each step. When performing this test, it is important to distinguish between ‘clunking’ originating in the hip joints and crepitus, which may be referred along the femora from abnormal stifles.

Fig 1

By walking behind the dog with the hands on its hips during gait analysis, the observer should be able to palpate any subluxation and reduction of dysplastic hips

Mild lameness cannot always be detected when a dog is walking but may become more apparent when it is made to trot, as more force is placed on the limbs at greater velocity. However, differentiation between fore- and hindlimb lameness may be more difficult at a trot. In contrast to the head movement seen in dogs with forelimb lameness, although less marked, the head will tend to nod down when the affected hindlimb contacts the ground as the dog attempts to redistribute weight to the forequarters using the head and neck as a counterbalance. In more severe cases, particularly at greater speed, lameness may manifest as a ‘bunny hopping’ gait in which animals move both hindlimbs simultaneously in adduction. This gait, which reduces weightbearing by each individual hindlimb and also reduces extension of the hip joints, is often associated with severe hip dysplasia. Observation at faster gaits (canter and gallop) may be performed in selected cases but is less useful because the speed of movement makes it difficult to assess the motion of individual limbs. Following gait analysis, the severity of the lameness should be graded (see Part 1, and Table 1, above right).

Table 1

Grading lameness at a walk and trot

Neurological deficits are seen more commonly in the hindlimbs than the forelimbs, largely as a consequence of the frequency of thoracolumbar and lumbosacral disc disease and the location of ascending neurological tracts. If hindlimb ataxia is suspected, a thorough neurological assessment should be performed. History-taking should involve questions relating to urination and defecation, as well as hindlimb coordination, especially scuffing of the claws or crossing of the legs when walking or trotting. It is worth noting that, although dogs may vocalise in other ways, yelping is not a feature that is usually seen in cases with OA. Unprovoked yelping generally indicates pain of neurological origin, and warrants thorough and prompt neurological investigation.

Box 2: Key visual signs of hindlimb lameness

  • Stride/step alterations

    • Short-stepping (‘limp’)

    • Ratio of stance to swing portion

  • Gluteal musculature

    • Jerking upward during weightbearing

  • Altered limb movement

    • Circumduction

    • High-stepping versus claw scuffing

  • Altered limb placement

    • External rotation

    • Internal rotation

Physical examination

Following gait examination, the examiner should know which limb(s) is/are affected. Physical examination of the affected limb should be performed in conjunction with examination of the contralateral limb (but beware of bilateral lameness). Examination should be performed in a systematic and consistent manner (eg, from distal to proximal) to make sure that nothing is missed. The contralateral limb should be palpated first so that the dog becomes accustomed to being handled before any painful areas are touched. The purpose of the physical examination is to localise the affected area of the joint or long bone.

Palpation of musculature

Palpation for muscle atrophy should always include the gluteal muscles, the quadriceps and the hamstrings (biceps femoris, semimembranosus and semitendinosus muscles). Disuse (or reduced use) atrophy will produce a palpable asymmetry in the musculature within a few weeks. Muscle mass is generally slower to recover, and apparently normal animals will frequently show atrophy for a number of months following apparent resolution of lameness as muscle bulk returns. In general, the muscles that are most vulnerable to atrophy are antigravity muscles that cross a single joint such as the quadriceps (excluding the rectus femoris which crosses the hip and stifle joints). Muscles that are least vulnerable to atrophy are flexor muscles that cross more than one joint such as the hamstrings.

Palpation of bones

An attempt should always be made to differentiate bone pain from surrounding soft tissue or adjacent joint pain. Bone conformation should be assessed visually and by palpation, although imaging, particularly computed tomography (CT), is more useful for investigating angular deformity or torsion. Femoral conformation is significant in the aetiology of medial patellar luxation (genu varum) and lateral patellar luxation (genu valgum). Although other sites can be affected, swelling and discomfort at the distal femur or proximal tibia in an adult dog warrants further assessment for bone neoplasia. A marked pain response on palpation of bone is a feature of panosteitis, which is seen predominantly in juvenile German shepherd dogs.

Palpation of joints

Effusion may be palpable, obscuring the definition of the straight patellar ligament in the stifle and circumferentially at all levels of the tarsal joints. In contrast, hip joint effusion is not appreciable by palpation. Harder thickenings indicative of chronic conditions may be apparent at, for example, the proximal medial tibia in cases of long-standing cranial cruciate ligament disease (‘medial buttress’). Avulsion fractures of the medial or lateral malleolus may be associated with substantial firm swelling, often accompanied by crepitus and discomfort on palpation. Firm digital palpation should be repeated to consistently elicit resentment until the examiner is satisfied that the location of the source of discomfort has been correctly identified.

Manipulation of joints

Joint manipulation is likely to be the most uncomfortable part of the physical examination and should therefore be performed last. All joints should be tested in flexion and extension, internal and external rotation, and adduction and abduction, where indicated. The range of motion possible, resentment to manipulation, the presence of crepitus and end-feel should be noted (see Part 1, and Table 2 below).

Table 2

Variation in end-feel*

Examination of specific joints

Hip

Hip joint manipulation should isolate flexion–extension from adduction–abduction and should also assess internal and external rotation. Even in the absence of hindlimb proprioceptive deficits, physical examination should be aimed at differentiating between caudal lumbar/lumbosacral pain and hindlimb pain. Hip extension inevitably results in lumbosacral extension, which will be resented in dogs with lumbosacral spinal pain as well as those with hip pain, while hindlimb abduction will generally not be resented by a dog with lumbosacral disease (unless there is concurrent hip OA). Many dogs appear to function reasonably well despite relatively advanced coxofemoral joint OA, but show severe resentment to attempted hip joint extension. It is therefore prudent to perform hip joint manipulation slowly and gently. Three manoeuvres commonly used for assessing laxity of the hip joint in young dogs are the Barden sign (‘hip-lift test’), Barlow sign and the Ortolani sign (see Boxes 3, 4, 5). Sedation or general anaesthesia is usually required to perform these tests adequately as pain and muscle spasm will detract from their value in the conscious animal. These tests are of limited value in dogs with complete luxation of the hip joints or in dogs with advanced OA.

Box 3: Barden sign

With the dog in lateral recumbency, the uppermost thigh should be grasped with one hand and lifted laterally without abduction, while the thumb or forefinger of the other hand is placed on the greater trochanter. A positive Barden sign is elicited when the thumb or forefinger is elevated more than 4 to 6 mm.

Box 4: Barlow sign

This test is essentially the first part of the Ortolani sign involving subluxation of the femoral head. The hip is placed in an abducted starting position and slowly adducted. In dogs with joint laxity, a distinct click may be felt as the femoral head subluxates and leaves the acetabulum, which constitutes a positive Barlow sign.

Box 5: Ortolani sign

The Ortolani sign is elicited with the dog in dorsal recumbency and both femora positioned perpendicular to the table top. In dogs with joint laxity, firm pressure applied to the stifles along the axis of the femora towards the hips results in subluxation of the joints. With the stifles still held firmly, the limbs are then slowly abducted. In dogs with joint laxity, a distinct click is felt as the femoral head returns to the acetabulum, which constitutes a positive Ortolani sign. The test can also be performed with the dog in lateral recumbency with the limb in question uppermost.

Consideration of iliopsoas strain should be made in dogs that resent hip extension, abduction and internal rotation (Breur and Blevins 1997). Specific palpation of the iliopsoas muscle belly, the iliopsoas tendon and the point of tendon insertion on the lesser trochanter will elicit significant discomfort in cases of iliopsoas strain.

Stifle

Manipulation of the stifle joint should always include attempts at medial and lateral luxation of the patella with the joint held in both flexion and extension. The examiner should be satisfied that the patella is seated firmly within the femoral trochlea, and that it glides smoothly as the joint is flexed and extended. The stifle joint should be stable in the transverse plane. Any laxity in this plane is indicative of collateral ligament injury. Cranial drawer (Box 6) and cranial tibial thrust (Box 7) are commonly used manoeuvres to assess the cranial translation of the tibia with regard to the femur. This is a diagnostic feature of cranial cruciate ligament rupture.

Box 6: Cranial drawer

This test involves placing the thumb of one hand on the lateral fabella, with the index finger on the patella, and placing the thumb of the other hand on the caudal tibial plateau, and the index finger on the tibial tuberosity. The tibia should then be moved cranially with respect to the femur. More than a few millimetres of movement with a poorly defined end point represents a positive result. A false negative result may be seen in some dogs with chronic cranial cruciate ligament disease where there is extensive periarticular fibrosis with or without meniscal injury blocking cranial tibial translation and also in dogs with partial cranial cruciate ligament rupture. Animals with rupture of the craniomedial band of the cranial cruciate ligament will only have a cranial drawer sign when the stifle is partially flexed. It should be noted that increased laxity is present in young large breed dogs, but the end point remains well defined. Sedation or anaesthesia may be required to elicit laxity, especially in dogs with recent rupture owing to pain and muscle spasm. In very large breeds, the test is more difficult to perform unless the dog is anaesthetised. However, cranial tibial thrust can be elicited in the conscious animal.

With the distal femur grasped between thumb and forefinger of one hand and the proximal tibia grasped between the thumb and forefinger of the other hand, an attempt should be made to induce cranial translation of the tibia with regard to the femur (arrows). Increased movement and a poorly defined end point are indicative of cranial cruciate ligament disease

Box 7: Cranial tibial thrust

With the stifle joint held at a normal standing angle (120°), the thumb of one hand should be placed on the lateral fabella and the index finger of the same hand on the tibial tuberosity. Then, with the metatarsus grasped in the other hand, flexion of the hock should be forced with the stifle fixed in position. This compresses the tibia, resulting in a cranial force on the proximal tibia. In the absence of a functional cranial cruciate ligament, there will be cranial tibial translation (ie, the gap between the thumb and index finger will increase). Tibial thrust is well tolerated and can often be performed without sedation or anaesthesia even in the larger breeds. Once a positive test has been elicited, it is worth initiating tibial compression with the stifle joint extended and allowing the joint to flex and extend while maintaining compression. This action may precipitate displacement and replacement of the caudal horn of the medial meniscus, sometimes palpable as a ‘click’. Absence of this finding does not rule out meniscal disease.

In the absence of a functional cranial cruciate ligament, flexion of the hock (arrow) with the stifle in partial flexion results in cranial translation of the proximal tibia with regard to the distal femur

Hock

The three components of the common calcanean (or Achilles) tendon (the superficial digital flexor tendon, conjoined tendon of the biceps femoris, semitendinosus and gracilis muscles, and the gastrocnemius tendon) should be assessed. Swelling of the insertion of the tendon of the gastrocnemius tendon on the tuber calcis and resentment on palpation are seen with Achilles tendinopathy. This may be associated with a partially plantigrade stance with characteristic flexing of the digits if the superficial digital flexor tendon is intact. Common ligamentous injuries in this region may involve the collateral ligaments of the tarsocrural joint, including avulsion fractures of the medial (tibial) or lateral (fibular) malleoli (Fig 2). Injury to these ligaments is typically acute in onset, often resulting in mild lameness for which the dog may not be immediately presented. Where medial or lateral instability can be demonstrated on manipulation, it should be possible to accurately determine whether the instability is more apparent with the hock in flexion (indicative of injury to the short component of the collateral ligament) or in extension (indicative of injury to the long part). Medial or, more commonly, lateral luxation of the superficial digital flexor tendon within the tendon sheath as it courses over the proximal end of the tuber calcis is an uncommon cause of hindlimb lameness.

Fig 2

Avulsion fracture of the lateral fibular malleolus (arrow) is often associated with varus instability owing to the attachment of the lateral collateral ligament at this site

Damage to the plantar ligaments will result in hyperextension of the tarsometatarsal or intertarsal joints. Avulsion and other fractures of the bones of the tarsus are generally presented as acute incidents due to the greater level of discomfort usually apparent.

Metatarsus and pes

The interphalangeal joints are uncommon sources of lameness. Chronic, fluctuating lameness as a sequela to OA of these joints or malunion/non-union of previous digital fractures is not seen very often. Foreign bodies in pads and migrating interdigital foreign bodies must not be omitted from the list of differential diagnoses for chronic hindlimb lameness.

Radiography

Radiography is typically the primary imaging modality for the investigation of lameness. Orthogonal views should be obtained for all investigations.

Pelvis and coxofemoral joint

Standard radiographic views of the pelvis are ventrodorsal (with the hindlimbs extended and placed in a frog-leg position) and lateral (see Box 8).

Box 8: Views of the pelvis

Lateral

  • Patient in lateral recumbency

  • Limb in question closest to the plate

  • Neutral coxofemoral joints with the femora parallel (as shown in Fig 3)

or

  • Dependent hip somewhat flexed and upper hip somewhat extended, which gives more information by splitting the femora in the radiograph

Ventrodorsal

  • Patient in dorsal recumbency

  • Hindlimbs extended with femora parallel, often held in position with tape

and/or

  • Hindlimbs abducted to give the ‘frog-leg’ view

PennHIP views

See box on the right

PennHIP

The Pennsylvania Hip Improvement Program involves acquiring ventrodorsal radiographs of the canine pelvis with the hindlimbs in three different positions to quantify the degree of laxity in the hips. The three PennHIP views are:

  • Ventrodorsal pelvis with the hindlimbs extended. In this view, the coxofemoral joint capsule is twisted by the act of extending the hindlimbs, and the resulting tension in the joint capsule pulls the femoral heads into the acetabula, artefactually improving coxofemoral approximation. This view is the standard for assessing the degree of bone change consistent with OA;

  • Ventrodorsal pelvis compression view. This view maximally reduces the femoral heads into the acetabula;

  • Ventrodorsal pelvis distraction view. This view maximally subluxates the femoral heads from the acetabula.

Fig 3

Positioning for lateral (above) and ventrodorsal (below) radiography of the pelvis and hips. Note the use of a measuring aid and left/right markers in the image above, which are used to aid measurement of structures and to clarify left versus right positioning in digital images

The distraction index (DI) is calculated from the last two views. DI is a direct measurement that compares the location of the femoral head within the acetabulum in the compression and distraction views normalised for the femoral head radius. The DI is an accurate measurement of hip laxity and, in young dogs, has been shown to correlate well with the development of OA in later life.

PennHIP was developed in the USA and is increasingly available in other parts of the world. PennHIP has been restricted in the UK by the need for manual positioning of the hindlimbs during radiography. A recently devised technique for hands-free PennHIP has meant that some practitioners in the UK are now performing PennHIP on a regular basis. The PennHIP website contains a complete list of all certified PennHIP practitioners in the world (www.pennhip.org).

The lateral view of the pelvis (see Fig 3 for positioning) may be used for determining the position of a luxated hip and for evaluating pelvic symmetry where, for example, there is a history of previous pelvic fracture or sacroiliac luxation. Ventrodorsal views of the pelvis and hips (see Fig 3 for positioning) are commonly viewed to determine the degree of laxity in the coxofemoral joints and to examine the joints for signs of OA. Common signs of coxofemoral OA include a curvilinear opacity at the site where the joint capsule attaches on the femoral neck (known as Morgan's line, Fig 4), remodelling of the cranial and caudal acetabular rim, flattening of the femoral head and irregular widening of the femoral neck. Positioning is critical, with obliquity appearing to open or close sacroiliac joints and increase or decrease acetabular femoral head coverage. If the pelvis is rotated, there will be an apparent asymmetry in the sizes of the obturator foramina and an increase in the width of the ilial wings on the side furthest away from the plate and an apparent increase in femoral head coverage on the contralateral side (Fig 5).

Fig 4

Caudolateral curvilinear osteophytes at the site where the joint capsule attaches on the femoral neck (Morgan's line) is indicative of early coxofemoral osteoarthritis

Fig 5a and Fig 5b

Satisfactory ventrodorsal radiographic view, with the hips extended. Rotation of the pelvis in the same dog has had the effect of apparently worsening coxofemoral conformation on the left and improving coxofemoral conformation on the right

Radiographic features of hip dysplasia tend to correlate poorly with clinical signs, and dogs with severe subluxation may show no clinical lameness. Therefore, a finding of a wide coxofemoral joint space on a radiograph is not sufficient to diagnose hip dysplasia as the cause of lameness.

Stifle and tibia

Caudocranial and mediolateral views are typically acquired for examination of the stifle (Fig 6, Box 9). In caudocranial views of the stifle, the fabellae should be bisected by the femoral condylar cortices and the patella should lie centrally. In the mediolateral view, the femoral condyles should be superimposed over one another, but should not overlie the tibial plateau. The triangular fat pad within the cranial stifle joint is commonly assessed to determine the presence or absence of an effusion or soft tissue within the joint. Effusion will also cause caudal displacement of the fascial plane within the gastrocnemius muscle caudal to the joint space. Periarticular osteophytosis typically occurs on the distal pole of the patella, the fabellae and on the caudal aspect of the tibial plateau.

Fig 6a, b

Positioning for mediolateral and caudocranial radiography of the stifle, including full-length views of the tibia, which enables measurement of the tibial plateau angle

Box 9: Views of the stifle

Mediolateral

  • Patient in lateral recumbency

  • Limb of interest closest to the plate

  • Contralateral limb pulled cranially or abducted

Caudocranial

  • Patient in sternal recumbency

  • Limb of interest extended caudally with the pelvis raised using a foam wedge

Tarsus and pes

The tarsus consists of three rows of seven bones stabilised by a sheath of soft tissues, collateral ligaments and numerous small ligaments. Radiographic interpretation, as in the carpus, is limited by superimposition of the other bones. CT, where available, is the modality of choice for imaging tarsal bone injuries.

Stressed dorsoplantar views are used to reveal tarsal valgus or varus instability associated with collateral ligament injury or malleolar avulsion fracture (Box 10).

Box 10: Views of the tarsus

Dorsoplantar (views in neutral ± stressed/unstressed valgus/varus)

  • Patient in dorsal recumbency

  • Limb pulled caudally to place the paw horizontally on the table

Mediolateral (± stressed flexed/extension)

  • Patient in lateral recumbency

  • Limb of interest closest to the plate

Arthroscopy

Arthroscopy is of limited application in the hip and tarsal joints. Hip arthroscopy has been used to assess the joint before triple pelvic osteotomy to address hip dysplasia and for arthroscopically guided biopsy of femoral head lesions (Scherrer and others 2005). Arthroscopic removal of avulsed bone fragments in cases of coxofemoral luxation has also been reported. Tarsal arthroscopy is challenging because of the small size of the joint, but can be used to evaluate the articular surfaces of the tibiotarsal joint and to identify and remove osteochondral flaps associated with osteochondritis dissecans.

Arthroscopy of the stifle joint is commonly performed before surgery to address stifle instability occurring secondarily to cranial cruciate ligament disease. A thorough assessment of the cruciate ligaments and the menisci may be performed arthroscopically (Fig 7) with removal or debridement, as necessary. The articular fat pad obscures the view (particularly when there is inflammation present in the joint) and may be debrided using a motorised shaver to improve visibility. Meniscal injury in the absence of cranial cruciate ligament rupture accounts for a significant proportion of knee joint arthroscopy in humans, but is rare in dogs. Arthroscopy allows minimally invasive investigation of the intra-articular stifle features in cases where a partial tear of the cranial cruciate ligament is suspected. Partial tears typically progress to complete rupture if treated non-surgically, although the timeframe varies from weeks to years. Onset and progression of OA in the canine stifle in the absence of the stabilising effect of the cranial cruciate ligament is rapid (with radiographic signs of periarticular osteophytosis developing within four weeks of the initiating cause). Arthroscopy of the stifle carries minimal morbidity and, therefore, should be performed sooner rather than later in the course of stifle-related lameness.

Fig 7

Arthroscopic view of the cranial and caudal cruciate ligaments, showing partial rupture of the cranial cruciate ligament

Synoviocentesis

Synoviocentesis was discussed in Part 1, and carries similar indications for the investigation of hindlimb lameness. Joint fluid samples should be grossly assessed for colour, turbidity, viscosity and volume, and should be submitted to a laboratory for cytology, and for culture and sensitivity testing, if deemed abnormal. Haematogenous spread of sepsis to severely osteoarthritic hip joints occurs with some frequency. Acute non-weightbearing lameness in cases of chronic OA should be considered an indication for synovial fluid cytology, culture and sensitivity testing. Samples should be submitted in blood culture medium to improve diagnostic yield (Montgomery and others 1989).

The hip joint may be sampled via a craniolateral approach to avoid the sciatic nerve situated caudally. By slightly abducting and externally rotating the femur, the dorsal joint space may be opened, thus allowing needle insertion dorsal to the greater trochanter. The needle will contact the dorsal acetabular rim and may be walked ventrally into the joint space from that point. Needle size depends on the size of the dog, but the authors commonly use 21 gauge, 40 mm needles for medium to large breed dogs.

Stifle synoviocentesis may be performed with the joint in a neutral position. The needle (23 gauge, 25 mm) should be inserted just lateral to the straight patellar ligament midway between the tibial tuberosity and the patella at a 45° angle to the skin with the tip directed towards the lateral parapatellar joint pouch (Fig 8). In view of the frequency with which hindlimb lameness associated with the stifle joint is encountered in veterinary practice, synoviocentesis of this joint should be within the general practitioner's repertoire.

Fig 8

Stifle arthrocentesis should be performed in a sterile manner with the needle inserted into the joint space lateral to the distal pole of the patella

The tarsus is sampled with the tibiotarsal joint held in 90° flexion. The needle (23 gauge, 16 mm) should be inserted plantaromedially, parallel to the calcaneus into the gap between the medial aspect of the lateral malleolus and the distal tibia.

Further imaging

Further diagnostic imaging of the canine hindlimb (eg, CT, ultrasonography, magnetic resonance imaging [MRI] and nuclear scintigraphy) may provide useful information in some cases. CT has been used for assessing acute and chronic malleolar avulsion fractures and can give a more accurate prognosis for the likely success of surgical reduction of such fragments. CT is also invaluable for accurately assessing the individual bones of the hock (eg, in cases of central tarsal bone fracture/luxation, Fig 9) where superimposition in plain radiography is limiting. Recent literature regarding contrast CT or MRI for assessing stifle anatomy (particularly meniscal injury) has been encouraging, although these modalities are unlikely to replace arthroscopy for the evaluation of the menisci because complete assessment requires manual probing. Where evidence of neurological dysfunction is associated with hindlimb lameness, imaging involving myelography or, preferably, MRI of the lumbar and lumbosacral spine should be performed.

Fig 9

3-D computed tomography reconstruction of the right hock, showing central tarsal bone fracture/luxation (arrow) in a four-year-old male collie-cross following trauma

Box 11: Differential diagnosis

Lameness localised to the joints of the hindlimb

Coxofemoral joint

  • Hip dysplasia +++

  • Legg-Calvé-Perthes disease ++

  • Coxofemoral luxation ++

Stifle

  • Cranial cruciate ligament disease +++

  • Meniscal injury (medial injuries are more common than lateral ones) +++

  • Patellar luxation (medial luxation is more common than lateral luxation) +++

  • Femoral condylar osteochondrosis/osteochondritis dissecans (lateral condyle more common than medial condyle) +

  • Spontaneous fracture of the lateral fabella +

  • Patellar fracture +

  • Patellar tendon rupture/avulsion +

  • Medial/lateral collateral ligament rupture +

  • Stifle luxation +

  • Avulsion/displacement of the long digital extensor tendon +

Tarsus

  • Talar osteochondrosis/osteochondritis dissecans ++

  • Tarsocrural luxation/subluxation (and associated malleolar fracture) ++

  • Shear injuries ++

  • Intertarsal subluxation ++

  • Central tarsal bone fracture/luxation ++

  • Calcaneus fractures +

  • Talus fractures +

  • Fractures of the numbered tarsal bones +

  • Avulsion of the gastrocnemius tendon +

  • Achilles tendinopathy +

  • Superficial digital flexor tendon avulsion/luxation +

  • Tarsometatarsal luxation +

Any joint

  • Osteoarthritis +++

  • Septic arthritis ++

  • Articular fracture ++

  • Joint neoplasia +

  • Polyarthritis +

Lameness localised to the bones/soft tissues of the hindlimb

Pelvis

  • Sacroiliac luxation +++

  • Fracture

    • Ilial +++

    • Acetabular +++

    • Pubic/symphyseal +++

    • Ischial +++

  • Fracture of the ischial tuberosity +

  • Von Willebrand's heterotopic osteochondrofibrosis +

  • Neoplasia +

Femur

  • Distal femoral physeal fracture +++

  • Aseptic necrosis of the femoral head +++

  • Femoral diaphyseal fracture +++

  • Femoral capital physeal fracture/separation ++

  • Neoplasia ++

  • Gracilis/semitendinosus myopathy +

  • Iliopsoas strain +

Tibia/fibula

  • Tibial tuberosity with or without proximal tibial physeal fracture +++

  • Diaphyseal fracture +++

  • Panosteitis ++

  • Medial/lateral malleolar fracture ++

  • Neoplasia ++

  • Metaphyseal osteopathy +

  • Distal tibial varus/valgus secondary to premature closure of the distal tibial/fibular physis +

  • Hypertrophic pulmonary osteopathy +

Metatarsals

  • Fracture +++

  • Luxation ++

  • Metaphyseal osteopathy +

  • Neoplasia +

Digits

  • Chronic/acute fracture +++

  • Luxation ++

  • Sesamoid disease ++

  • Osteomyelitis – haematogenous spread of infection +

  • Septic arthritis +

  • Neoplasia +

All bones

  • Osteomyelitis +

  • Bone cyst +

Immature dog, Mature dog, + Rare, ++ Seen with some regularity, +++ Common

Note some conditions may be seen in both immature and mature dogs

Ultrasonography may be of use in investigating hindlimb lameness that is thought to be associated with trauma to tendons or ligaments, particularly the straight patellar ligament/quadriceps tendon and the common calcanean tendon. The straight patellar ligament may occasionally be partially or completely ruptured or avulsed following trauma. Radiographic features of straight patellar ligament rupture include patella alta and stifle joint effusion. Depending on the chronicity of the condition, thickening and a deficit in the straight patellar ligament may be apparent on ultrasonography (Fig 10).

Fig 10

Ultrasonographic image of avulsion of the straight patellar ligament (SPL) from the tibial tuberosity. This is a rare traumatic condition causing severe stifle instability and hindlimb lameness

Ultrasonographic assessment of the common calcanean tendon may similarly help to determine the extent of trauma to the three individual components.

Bone biopsy

Bone biopsy was discussed briefly in Part 1. Despite the mantra that primary bone tumours occur commonly in the distal femur and proximal tibia (‘away from the elbow, close to the knee’), areas of lytic bone at any site should be sampled if neoplasia is suspected.

Summary

Effective treatment of hindlimb lameness requires accurate diagnosis. Lameness associated with the hindlimbs is most commonly associated with two common conditions: cranial cruciate ligament disease and hip dysplasia. It is, however, inappropriate to make assumptions about the aetiology of hindlimb lameness without a thorough investigation, which should begin with gait analysis and palpation/manipulation of the hindlimbs in the conscious animal. Radiography, advanced imaging and biopsy sampling may follow, as appropriate. A structured approach to the investigation of hindlimb lameness will aid consistent diagnosis.

Acknowledgments

The authors would like to thank Steve Joslyn and Mark Bush for their suggestions during the preparation of the original manuscript of this article and the nurses at Southern Counties Veterinary Specialists for their help with the images.

References and further reading

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