Pelvic limb lameness is a frequent reason for pet owners to seek veterinary care. Common causes of the lameness include cranial cruciate ligament disease (CrCLD), canine hip dysplasia (CHD), degenerative lumbosacral stenosis (DLSS) and/or iliopsoas muscle-tendon strain (IS). As a veterinarian, the challenge is to determine which disease is the major contributor to the patient's presenting concern.
The patient age, breed and gender is not tremendously helpful is deciphering the source of the problem since many of the aforementioned ailments are common in young to middle aged, active, large breed dogs of any gender.
Obtaining an accurate and detailed patient history is of vital importance. Clarifying the owner's observations and concerns can be extremely helpful. For instance, the patient that has chronic, mild stiffness in both hindlimbs when rising, but now has a recent onset of a unilateral lameness may suggest CrCLD superimposed upon chronic CHD. Conversely, the normally active "frisbee" dog that displays very little stiffness or lameness, but now is reluctant to jump may suggest LS disease and/or iliopsoas strain injury. In addition to clarifying the pet owner observations (stiffness, lameness, reluctance to jump, etc.), it is important to determine the nature of the onset (peracute, acute, insidious), progression (episodic, waxing/waning, progressive, improving), and duration of the identified problem. It is also helpful to identify factors that seem to exacerbate the problem (activity, patient cool down, rising in the morning, etc.) as well as its response to any therapies (rest, prescribed medications, over-the-counter medications and even medications that may have been prescribed for another pet).
Gait and Mobility
I like to observe my patients as they approach the hospital, as they walk to the exam room and while obtaining a patient history. It is during this time that they are moving about naturally because they do not know how closely that I am watching them. For example, the pet may shift weight away from one pelvic limb as evidence of discomfort. Alternatively, the patient may put his front limbs up on the counter in search of a treat...strongly suggesting that neither hip extension nor lumbar extension is uncomfortable. The patient may have difficulty sitting...shifting his/her weight to the thoracic limbs to do so; this finding is strongly suggestive of a bilateral pelvic limb problem such as CHD or bilateral CrCLD (Figure 1 [VIN editor: Figure 1 was not provided at the time of publication.]). All of these observations are relevant and significant clues as to the source of their discomfort.
General physical exam findings may give clues as to the etiology of the presenting pelvic limb problem. For example, fever and lethargy may suggest a septic, immune-mediated or neoplastic etiology. Poor femoral pulse quality in one limb may suggest a primary or secondary vascular etiology.
While there are numerous specific orthopedic palpation tests applicable to the pelvic limb (drawer test, tibial compression test, Ortolani sign, etc.), the importance of simply determining the anatomic location of the patient discomfort is often overlooked. Imagine that you have developed lameness and discomfort in your own leg, the location of the discomfort is among the most relevant of pieces of information that you would likely relate to your physician. Unfortunately, our patients are unable to articulate the location of their pain. Therefore, it is our job to help our patients develop enough trust in us that they are willing to otherwise indicate "it hurts here." While this principle is the focus of another lecture ("Tell Me Where It Hurts" - The Art of the Canine Lameness Exam), it can be summarized as taking the time to develop a friendly relationship with your patients before pursuing your role as a doctor. In essence, if you patient trusts you, he or she is less likely to mask the location of their discomfort or squeal as a result of his/her anxiety and nervousness.
I prefer to palpate the pelvic limbs for asymmetry with the dog in a balanced stance whenever possible (Figure 2 [VIN editor: Figure 2 was not provided at the time of publication.]). This allows me to detect subtle differences in muscle mass, joint swelling, tissue warmth, etc. The normal stifle has a discretely palpable patellar ligament that feels similar to a pencil with small indentations on each side that feel similar to a bruise on an apple (Figure 2 [VIN editor: Figure 2 was not provided at the time of publication.]). The loss of these normal findings indicates periarticular fibrosis, joint effusion or both. Medial buttress, associated with CrCLD chronicity, is palpable as an exaggerated bump extending across the medial aspect of the stifle joint.
Pain upon forced full flexion or extension of the stifle is a simple test that is suggestive of early CrCLD (Figure 3 [VIN editor: Figure 3 was not provided at the time of publication.]). Stifle lameness is suspected when dogs display a painful response to stifle flexion because dogs with a healthy stifle should tolerate full passive stifle flexion even if somewhat forceful. If pain is detected upon combined tarsal and stifle flexion (Figure 3 - left [VIN editor: Figure 3 - left was not provided at the time of publication.]), the maneuver should be repeated with only stifle flexion. A pain response to full stifle extension may suggest CrCLD, but the examiner must be aware that discomfort may occur even with a healthy stifle if too much extension force is used.
The cranial drawer test and tibial compression tests are important for assessing palpable instability (Figure 4 [VIN editor: Figure 4 was not provided at the time of publication.]) and have been described elsewhere. Partial tears of the CrCL often reveal cranial drawer instability only when the stifle is held in flexion. Periarticular fibrosis in chronic CrCLD or minimal CrCL tearing in early CrCLD may not permit detection of stifle instability. Thus, the absence of palpable instability does not necessarily preclude the clinical diagnosis CrCLD or its surgical treatment.
Finally, the examiner should be sensitive to detecting "clicks" typical of meniscal injury. Gross injury to the medial meniscus is very common in conjunction with CrCL pathology especially in large breed dogs with chronic CrCL pathology and/or gross stifle instability. One should be aware, however, that the absence of a meniscal click does not rule-out meniscal injury.
Discomfort in the pelvic region can arise from the coxofemoral joint, the lumbosacral spine and/or the iliopsoas muscle tendon unit as well as other locations. Knowledge of the regional functional anatomy will guide a careful exam making it possible to better discern the anatomic source of the pain. The iliopsoas muscle passes along the ventral aspect of the lumbar spine, coursing along the ventrum of the pubic brim and the tendon inserts upon the lesser trochanter of the femur such that hip extension, especially when combined with internal rotation places the muscle-tendon unit (MTU) under tension. Thus, mild pain upon hip extension that is exacerbated by internal rotation is suggestive of IS. Intense pain detected upon gentle palpation of the pubic rim region on the affected side during rectal exam is further support. Very soft digital palpation pressure over the lesser trochanter or sublumbar spine may also elicit discomfort or palpable muscle spasm in IS patients. Extension of the lumbosacral spine often exacerbates cauda equine compression in dogs with DLSS because of dynamic protrusion of the degenerative intervertebral disc and the hypertrophic ligamentum flavum. LS extension also exacerbates foraminal stenosis due to osteophytosis and capsular hypertrophy of the articular facet joints. During patient examination, I am careful to observe whether pain arises during hip extension or if it occurs only during LS extension that often occurs during terminal hip extension. If discomfort is only detected after the LS spine begins to extend, the LS junction is a likely source of pain. If pain arises before LS spine extension, the hip may well be the source...especially if it is exacerbated by hip abduction.
Diagnostic imaging is useful in ruling out disorders such as CrCLD, CHD, and osseous neoplasia, however the presence of radiographic CHD does little to tell the veterinarian if it is the primary source of the patient's problems. Thus, imaging is used to support the findings of the careful examination rather than as a substitute for it.
A Rule of Thumb
In patients with mildly symptomatic, chronic CHD and acute onset of unilateral lameness associated with CrCLD, the stifle is usually treated first.