Canis ISSN: 2398-2942
Lameness: hindlimb - investigation
Contributor(s): Gareth Arthurs, Toby J Gemmill
Orthopedic examination of the pelvic limbs
- If possible, start with the dog standing and stand or crouch behind the dog. Palpate and assess pelvic limb muscle bulk / atrophy with the dog standing. Compare the size of quadriceps muscle group cranial to the femur and the hamstrings (semitendinosus and semimembranosus) caudal to the femur. These muscles are relatively easy to palpate even in obese dogs. This provides information as to which pelvic limb is affected because each affected limb will have a degree of muscle atrophy.
- The majority of the pelvic limb examination cannot be performed with the dog sitting; the dog should be positioned either standing or lying in lateral recumbancy. As for the thoracic limb, be methodical and thorough; start distally and work proximally or vice versa. This should ensure that lesions are not missed.
- Examine the digits carefully, methodically and systematically. The digits have a large range of movement in flexion and extension with a reasonable amount of medial and lateral movement:
- Check the interdigital skin for signs of dermatitis, wounds or lacerations.
- Check the interdigital hair for signs of saliva staining.
- Check the pads (individual digits and large stopper pads) for wounds or embedded foreign bodies.
- Check the claws and nail-beds for signs of disease/abnormalities.
- Check each of the interphalangeal and metatarsophalangeal joints individually for normal, pain-free range of movement in extension and flexion, and for instability medially and laterally. If unsure, compare any suspicious digit to the adjacent digit.
- Check each of the proximal and distal interphalangeal joints and the metatarsophalangeal joints individually for swelling, pain, heat or crepitus.
- Check the metatarsophalangeal joints specifically for pain on deep palpation in the region of the palmar sesamoid bones (particularly sesamoid bones 2 and 7 in affected breeds such as the Rottweiler) Sesamoid: disease.
- Moving proximally, palpate each of the metatarsal bones individually checking for swelling, thickening, pain, heat or overlying soft tissue (extensor/flexor tendon) abnormalities.
- The hock consists of the talocrural joint which allows a large range of flexion and extension, and the subtalar joints which have only a lmited range of motion. The subtalar joints consist of the proximal and distal intertarsal joints, the tarsometatarsal joint, and numerous small articulations between individual tarsal bones:
- Palpate the general region of the tarsal bones, the tarsal joints and the tarsometatarsal joint. From proximal to distal, the bones of the tarsus consist of the calcaneous, talus, central tarsal bone, 1st, 2nd, 3rd and 4th tarsal bones, and distally the proximal aspects of the 2nd, 3rd, 4th and 5th metatarsal bones. The proximal intertarsal joint consists of the calcaneo-quatral and talo-central joints, the intermediate joint is the centrodistal joint and the distal joint is the composite tarso-metatarsal joint. It is difficult to palpate the tarsal bones separately and distinctly except for the calcaneous and the lateral aspect of the 4th tarsal bones that can be palpated distinctly. Check for swelling, thickening, pain, heat , crepitus or soft tissue swelling. The intertarsal and tarsometatarsal joints are low motion joints hence little to no movement/instability should be palpable in the normal patient.
- The talocrural joint works as a constrained hinge joint; the joint has a large range of movement through full extension to flexion. Working distally to proximally, check:
- Talocrural range of movement; the normal talocrural joint should move from approx 40 degrees of flexion to 165 degrees of extension. Full talocrural extension and flexion is not possible without simultaneous passive stifle extension and flexion respectively but to test talocrural range of movement and pain, it is the talocrural joint that must be tested actively. Certain breeds such as the German Shepherd Dog have a slightly reduced range of talocrural movement.
- Medial and lateral hock stability; the dog's normal hock has no instability in flexion but in extension, a small amount of lateral laxity may be appreciated Hock: dorsal instability Hock: dorsoplantar and collateral instability Hock: plantar instability.
- Rupture of the short collateral ligaments can lead to rotator instability with the talocrural joint in flexion.
- Talocrural swelling / effusion; it is best to palpate this at one of the 4 pouches of the talocrural joint that are positioned dorsomedial, dorsolateral, plantaromedial or plantarolateral
- Pain, crepitus or limited range of movement with any of these manoeuvres.
- Invariably a small firm sesamoid bone can be palpated in the tendon of insertion of cranial tibial muscle at the point that this tendon crosses from lateral to medial over the dorsal aspect of the hock joint just proximal to its point of insertion on the proximal dorsal aspect of the 2nd metatarsal bone.
Tibia and fibula
- Gently palpate the tibia, working from the hock distally to the stifle proximally. Both the lateral and medial malleoli can be palpated distally. Extending proximally, the fibula can only be palpated for a short distance. Almost all the cranial and medial surfaces of the tibia can be palpated from distal to proximal. Landmarks to palpate proximally include the cranial tibial muscle on the proximolateral aspect of the tibia and the tibial tuberosity on the cranial aspect of the proximal tibia. The gastrocnemius muscle can be palpated caudal to the proximal tibia; although there are medial and lateral bellies, they are not readily distinguishable. Deep to gastrocnemius are the popliteal and digital flexor muscles but these cant be palpated directly. As the gastrocnemius muscle is palpated distally, its size and shape changes as it contributes to and becomes the Common Calcaneal tendon: this can be palpated right up to the point of insertion on the proximal aspect of the Calcaneus. Integrity of the common calcaneal tendon (hock extensor mechanism) can be readily checked: it should not be possible to flex the hock without simultaneous stifle flexion. If the hock will flex whilst the stifle is extended, this indicates common calcaneal tendon mechanism injury. Thickening of the tendon can be an indicator of tendon pathology Gastrocnemius tendon avulsion Hock: calcaneal tendon injury.
- The stifle joint is a complex hinge joint. The cranial landmarks of the stifle that should be palpable include the patella, the straight patellar tendon and the tibial tuberosity. These structures form the distal aspect of the quadriceps extensor mechanism on the cranial aspect of the stifle joint. On the lateral aspect of the stifle joint, the fibular head should be palpable on the distal aspect, the lateral condyle should be palpable just proximal to it, and just proximal again, the lateral fabella (the sesamoid of the lateral belly of the gastrocnemius muscle) should just be palpable.
- Either side of the patellar ligament, a small concave depression should be palpable, deep to which is the infrapatellar fat pad and stifle joint which are not palpable. When a stifle effusion is present, these depressions are either more difficult to appreciate or an effusion is directly palpable. In addition, the lateral and medial borders of the patellar ligament become less distinct to palpate Stifle: rupture of the patellar ligament.
- In obese dogs, all these landmarks can be more challenging to palpate due to subcutaneous adipose tissue overlying and obscuring them.
The stifle's full range of movement should be from flexion of 40 degrees where the crus (tibia and associated soft tissues) touch the hamstrings through to extension of about 160 degrees. Full range of movement should be possible without pain or instability. As the stifle is extended, the hock will extend secondarily. Check lateral and medial collateral ligament stability and integrity; there should be no instability Stifle: instability due to other ligament insufficiency.
- Patella: the patella should track normally in the trochlear groove through a full range of extension and flexion. Patellar luxation Patella: lateral luxation Patella: medial luxation is most easy to appreciate starting with the stifle in full extension and then gradually flexing the stifle. If the patella luxates as the stifle is flexed, the patella will typically stay luxated until the stifle is extended again. If the patella seems stable through a normal range of stifle movement, test further by placing gentle lateral and then medial pressure on the patella whilst the stifle is flexed. Subsequently test patellar stability by internally and then externally rotating the tibia whilst the stifle is flexed; not all dogs with tolerate this while conscious.
- Stifle test for cranial cruciate ligament insufficiency Stifle: cranial cruciate ligament disease : craniocaudal stability of the stifle should be tested - in general, this checks the integrity of the cranial cruciate ligament - but rarely caudal cruciate ligament instability occurs. There are two ways of testing craniocaudal stability of the stifle and although these can be performed in the conscious dog, they are more reliably performed with the dog sedated or anesthetized and in lateral recumbency.
- Cranial drawer Stifle: cranial drawer test : The stifle is grasped in two hands. For the right stifle, the dog is placed in left lateral recumbency. The clinician is positioned behind the dog. The proximal tibia is taken in the right hand with the thumb on the fibular head and the index finger on the tibial tuberosity. The distal femur is taken in the left hand with the thumb over the lateral fabella and the index finger on the patella. (These positions are reversed for the left stifle). It is very important that the fingers and thumbs are placed on the bony landmarks and not on the adjacent soft tissues. The stifle is grasped firmly but gently, and the hand on the tibia is positioned caudally in case the tibia is already subluxated. The proximal tibia is then pushed cranially relative to the distal femur. The stifle should be stable and movement should not be possible. A dog that has cranial cruciate ligament instability will show cranial movement of the proximal tibia relative to the distal femur, and frequently the end point is indistinct. Performing this test successfully requires practice and developing the correct technique; this is a test of technique and not operator strength! False positive results can occur:
- Young puppies have relatively lax stifles and may have apparent craniocaudal instability. This can be distinguished from pathological cruciate instability as there is no associated stifle effusion and the craniocaudal instability will have a well defined end point as the physiologically lax cranial cruciate ligament becomes abruptly taut during manipulation. In addition, the instability should be identical between left and right stifles.
- Adult dogs can have mild cranial instability of the tibia relative to the femur in association with mild internal rotational instability of the tibia - this is normal. This can be distinguished from pathological cruciate instability as there is no associated stifle effusion, the instability has a clearly defined end point, and there is no difference between the suspected and the contralateral stifle. In addition, if the test is repeated and internal rotation of the tibia is prevented by the hand on the tibia, craniocaudal instability will also be controlled and eliminated.
- A false negative result for cranial drawer cruciate instability can occur when there is a partial cranial cruciate ligament rupture, when the degree of stifle effusion or periarticular thickening / fibrosis is such that this contributes to stifle stability and therefore masks cranio-caudal stifle instability, or when the dog is large, tense or painful that instability cannot be elicited. Such dogs require re-examination under sedation Sedation / sedative protocols or general anesthesia General anesthesia: overview.
- Tibial thrust test Tibia: compression test. For the right stifle, the dog is placed in left lateral recumbency. The stifle is cupped by the palm of the left hand and the index finger is extended distally so that the tip of the finger exerts gentle caudal pressure on the tibial tuberosity. The foot is taken in the right hand with the calcaneus cupped by the palm and the fingers extend distally towards the digits. Start with the stifle fully flexed and then work incrementally through to full extension. At each incremental angle of stifle extension, firm pressure is applied to the plantar aspect of the tarsus using the fingers of the right hand - this mimics the force of weight bearing through the limb and causes slight hock flexion. Displacement of the tibial tuberosity is monitored by observing it and by using the third finger of the left hand to feel it. If the tibial tuberosity moves cranial relative to the femur, this is a positive cranial tibial thrust test. This can occur at different angles of stifle flexion/extension therefore the test should be repeated throughout the full range of stifle movement. A positive cranial tibial thrust test indicates cranial cruciate ligament disease / rupture.
- The condyle of the distal femur and the greater trochanter of the proximal femur are easily palpated in all but the most obese patients. The majority of the femoral diaphysis inbetween is not palpable due to overlying muscles which can be palpated separately; these include the quadriceps group cranial to the femur, tensor fascia lata and biceps femoris muscles lateral and caudal to the femur, semimembranosus and semitendinosus caudal to the femur, and adductor, gracilis and pectineus muscles medial to the femur. Abnormalities of these muscle groups are unusual; the most common palpable abnormality is muscle atrophy that reflects chronic pelvic limb lameness - there is usually a palpable reduction in the size of the quadriceps and hamstring muscle groups.
- The hip is a ball and socket joint comprising the acetabulum and femoral head; this allows the joint to move in three dimensions; extension/flexion, internal/external rotation and abduction / adduction. A normal hip has a wide range of pain and crepitus free movement; the hip should flex to about 50 degrees and extend to about 160 degrees.
- It is impossible to fully extend the hip without simultaneously extending the stifle and increasing patello-femoral contact pressure. If concurrent stifle pathology exists, this may cause stifle pain which will give a false positive pain response to hip extension. Therefore a positive pain response to hip extension must be interpreted carefully and stifle pathology ruled out to avoid a false positive result. If independent stifle extension shows no pain response, this makes such a false positive result for hip pain less likely. A false positive pain response to hip extension can also occur if lumbosacral pathology exists; this is because extending the hip also exerts pressure onto the lumbosacral spine. Therefore lumbosacral pain should be separately investigated by careful examination of the area.
- In addition, extension of the hip will create tension in the hip flexor muscles; discomfort can occasionally be seen on hip extension in animals with iliopsoas myopathies and tendinopathies. The discomfort in these patients is often exacerbated by internal rotation of the limb during full hip extension.
- Abduction of the hip will often elicit a pain response if hip pathology is present, but this manoevre does not stress the lumbrosacral or sacroiliac joints, the stifle joint, or the iliopsoas muscles.
- Bardens hip lift Barden test and Ortolani tests Ortolani test assess hip laxity, and are usually employed in skeletally immature dogs. They are an important part of the orthopedic work-up of a dog with hip dysplasia but not usually part of the initial assessment. These are potentially painful tests for the dog that should only be performed under sedation or general anesthesia. A full description of these tests can be found in orthopedic textbooks (Houlton 1994, Piermattei and others 2006).
- The thumb displacement test is used as a diagnostic test for craniodorsal hip luxation. The clinician's thumb is placed in the bony depression between the ischial tuberosity and the greater trochanter. In the normal dog, as the pelvic limb (and hip) is gently externally rotated, the greater trochanter of the femur moves caudally and impinges onto and displaces the thumb. If the dog has a craniodorsal hip luxation, the clinician's thumb is not displaced with external rotation of the pelvic limb because the greater trochanter of the femur is not in close enough proximity. Note that this test is not painful in the normal dog but may be painful for a dog with a luxated hip.
- Palpate the pelvis for symmetry, stability, and check the dog is not painful on palpation. Anatomical landmarks to palpate include the ischial tuberosity, the greater trochanter of the femur, and the cranial dorsal ilial spine. Palpate each of these structures, checking for discomfort, swelling, and change in texture, shape or position. The relative positions of these 3 landmarks make the shape of an inverted triangle in the normal patient. This relationship is lost in instances of pelvic fractures Pelvis: fracture or hip luxations. For example, if a dog suffers a craniodorsal hip luxation Hip: luxation , the greater trochanter moves dorsally and typically lies immediately inbetween the ischial tuberosity and the dorsal ilial spine, ie the inverted triangle shape is lost.
Further diagnostic tests
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Pelvic limb lameness - common differential diagnoses
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