Rupture of the cranial cruciate ligament is the most commonly diagnosed orthopaedic condition in dogs (Harasen, 2011a). This article describes how rehabilitation plays an important part in management of the condition, for both patients that are managed conservatively (part one) and in the aftercare of those that are managed surgically (part two).
The canine cranial cruciate ligament originates from within the intercondylar notch at the distal end of the femur and crosses the stifle joint space to insert on the intercondylar area at the tibial plateau (Alveraz, 2011). Its purpose, along with the caudal cruciate ligament, is to provide stability to the stifle joint and prevent movement of the tibia in a cranial direction (tibial thrust) (Shaw, 2017).
Rupture of the canine cranial cruciate ligament (CrCL) occurs most commonly as a result of degeneration of the ligament which frays and eventually ruptures; rather than as a result of trauma (Davidson et al, 2005). This degenerative process has led to development and use of the term ‘cruciate disease’ to describe the entire process, which varies in duration from an acute incident to a chronic process lasting many months (Corr, 2009).
Certain breeds and individuals are thought to be prone to the development of cruciate disease, with breeds such as the Rottweiler, Labrador Retriever and Golden Retriever amongst those that are over-represented (Harasen, 2011a). Width of the intercondylar notch, width of the tibial tuberosity, and the tibial plateau angle have all been suggested as important genetic aetiological factors affecting the likelihood of the development of cruciate disease (Harasen, 2011a). It has also been demonstrated that environmental factors including obesity, the feeding of high-energy diets and early neutering have been shown to increase the incidence. Dogs with grade 3–4 patellar luxation have also been shown to have a higher incidence of cruciate disease than their unaffected cohorts, as a result of stifle instability and internal rotation of the tibia (Harasen, 2011a).
Clinical signs and diagnosis
Given the prominent presentation of cruciate disease, it should be considered in every patient presented for investigation of hind limb lameness (Millis and Levine, 2014). Affected patients may present as acutely lame following exercise, or as intermittently lame over a period of time. Diagnosis can be achieved from performing a thorough orthopaedic examination, coupled with radiographs of the stifle to look for changes suggestive of cruciate disease and to rule out other causes of lameness (Norris, 2012).
Initial examination will reveal some or all of the following clinical signs:
- Stifle effusion
- Pain on examination of the stifle, particularly during extension
- Loss of muscle mass of the affected limb
- Fibrous thickening of the joint capsule and surrounding structures
- Formation of the ‘medial buttress’ — a fibrous thickening on the medial aspect of the proximal tibia associated with the medial collateral ligament (Norris, 2012)
- An altered sit position whereby the stifle and lower limb are extended laterally (Figure 1) (Shaw, 2017).
If cruciate disease is suspected, a more detailed orthopaedic examination, including the tibial compression test and cranial drawer test, may reveal more information (described below).
The tibial compression test is most easily performed with the patient in a standing position. The forefinger is placed on the patella with the tip of the finger resting on the tibial tuberosity. The hock is then flexed with the stifle in a fixed position, and in cases of CrCL rupture, the clinician may experience cranial displacement of the proximal tibia (Harasen, 2011b).
The cranial drawer test is best performed with the patient in lateral recumbency, lying on the unaffected side. The femur is held stationary in one hand, while using the other hand the clinician attempts to displace the tibia cranially. False positives can occur in young dogs, and false negatives as a result of partial tears (Harasen, 2011b).
A latero-medial radiograph of the stifle will usually demonstrate an effusion within the joint, loss or cranial displacement of the intrapatellar fat pad (Figure 2) and in some cases, osteophyte formation on the femoral condylar ridges (Corr, 2009). It can also be used to assess the level of degenerative joint disease present (which occurs invariably to some degree as a result of stifle instability) (Davidson et al, 2005), and to rule out other orthopaedic conditions (Millis and Levine, 2014).
Following diagnosis of cruciate disease, discussion must be had with the owners about the treatment options available. These options fall into two broads categories: surgical or non-surgical (conservative) management, the latter of which is generally accepted as a combination of some or all of the following:
- Non-steroidal anti-inflammatory drugs (NSAIDs)
- Weight management
- Cage rest
- Exercise modification
- Physiotherapy
- Hydrotherapy (Comerford et al, 2013).
Overall, surgical management has been shown to have better outcomes (Prydie and Hewitt, 2015). It has been estimated that 70–80% of dogs, particularly large breeds, will not show a significant improvement without surgical intervention (Marsolais et al, 2002). Meniscal (generally the medial meniscus) injury has been suggested as a reason for this, which is estimated to occur in around 45% of patients with cruciate rupture (Davidson et al, 2005). An additional clinical sign which may be present in patients that have also experienced a meniscal tear is an audible ‘click’ while assessing stifle range of motion. The treatment of choice is a meniscotomy (Millis and Levine, 2014), and therefore patients displaying signs that are strongly suggestive of a meniscal tear immediately become more obvious surgical candidates.
Another complicating factor regardless of the treatment option selected is that the incidence of cruciate rupture in the contralateral limb has been shown in one study to be approaching 60% (Harasen, 2011a).
The rehabilitation of patients following the most common surgical procedures used currently to manage cruciate disease will be discussed in detail in part two of this article series. Conservative management will be discussed in detail below.
Conservative management of CrCL
Conservative management of cruciate disease is best suited to small patients, without meniscal involvement, with one study reporting a return to normal loading and joint range of motion in over 85% of dogs weighing less than 15 kg (Vasseur, 1984). It may also be attempted in those patients where surgical management is contraindicated due to concurrent conditions or high anaesthetic risk. Goals for conservative management include analgesia, stabilisation of the stifle joint, improvement of the lameness, and maintaining stifle range of motion and managing muscle loss in the affected limb (Prydie and Hewitt, 2015).
Conservative management is generally initiated with 4–8 weeks of strict confinement (Millis and Levine, 2014). There are several types of external stifle braces available to purchase which may be used to support the stifle, but there is currently no evidence to suggest they may accelerate recovery or improve outcomes (Millis and Levine, 2014).
An example of a suitable rehabilitation programme for patients undergoing conservative management is described below. When referring patients for rehabilitation, it is imperative to ensure that the rehabilitation therapist is registered with an association such as RAMP, ACPAT, IRVAP or NAVP to ensure the highest standard of care delivered by qualified professionals.
Weeks 0–2
For the first 14 days following cruciate rupture, the focus of rehabilitation is pain relief, encouraging gentle weight bearing and adapting the exercise programme and environment at home to improve the patient's quality of life and prevent further injury (Prydie and Hewitt, 2015).
Pain relief is generally delivered in the form of NSAIDs, and can be supplemented by use of electrotherapy in the form of pulsed magnetic field therapy (PMFT) and laser therapy. PMFT provides analgesia, the suggested mechanism being the interference of pain signals along unmyelinated nerve cells via hyper-polarisation of cells. It is also hypothesised that pulsed magnetic therapy increases oxygenation in areas of damaged tissue, through increasing ion exchange (notable potassium, which leaks from damaged cells) (Prydie and Hewitt, 2015). Laser therapy may benefit the patient through the delivery of photons of light, which stimulate the mitochondria at a cellular level. This increases cell respiration and ATP production, which in turn is thought to act as a neurotransmitter, and so affect pain modulation. It may also have anti-inflammatory effects through a reduction in enzymes involved in the COX pathway (Millis and Levine, 2014).
The duration and intensity of daily exercise delivered to the patient should be modified. At this stage, exercise should be restricted to 5 minutes of gentle lead exercise at any one time, on an even surface, avoiding playing, jumping and boisterous activity. The home environment should be modified to also prevent this type of activity between walks, and may include the introduction of non-slip runners or mats, crate rest to prevent jumping on and off furniture, and lifting patients where possible to prevent use of stairs. Diet should be discussed with the owners of patients that are overweight to initiate weight loss (Prydie and Hewitt, 2015).
Gentle therapeutic exercise may be introduced at this stage including passive range of motion exercises (PROM) delivered to the hip, hock and digits (Prydie and Hewitt, 2015). This is best achieved with the patient in lateral recumbency with the affected leg uppermost. The aforementioned joints are slowly and smoothly moved through their available range of flexion and extension, through a saggital plane, avoiding internal and external rotation, while the weight of the limb is supported by the therapist. Performing these exercises in three repetitions, twice daily, will assist in the maintenance of the available range of motion within these unaffected joints, enhance proprioception, and allow the distribution of synovial fluid for joint nourishment (Marcellin-Little and Levine, 2015).
Parastanding can also be included, most easily performed by placing a block or book under the affected and unaffected limbs in turn, for 60 seconds, three times, twice daily. This exercise enhances proprioception (Prydie and Hewitt, 2015), and so encourages the initiation of gentle weight bearing. Applying sensory stroking techniques and gentle compressions through the digits will further enhance this proprioceptive enriching technique.
Hydrotherapy should also be initiated at this stage, to encourage gentle weight bearing in a supported environment, provided by the buoyancy properties of water (Wong, 2011), and to further enhance proprioception. This can be delivered via an underwater treadmill, with water height above the level of the stifle, or via free swimming (Prydie and Hewitt, 2015).
Weeks 2–4
From 2–4 weeks post rupture, rehabilitation goals include:
- The management of any ongoing pain as above
- Increased weight bearing
- The initiation of strengthening exercises for the hind limbs and exercises to promote core strength.
Twice daily lead walks should be increased to 10 minutes, while continuing to restrict high impact activity as before (Prydie and Hewitt, 2015).
Gentle strengthening exercises should be introduced at this stage to build core strength and address muscle loss in the affected hind limb. This would ideally involve a combination of weekly hydrotherapy to allow muscle to build in an environment which minimises impact on the joints (Wong, 2011), and a series of land-based exercises including the following:
- Sit to stand exercises — the therapist asks the dog to sit (and ensures a straight ‘tidy’ sit with both stifles flexed by correcting the patient's position if necessary) then encourages the patient to rise into a stand position. This exercise strengthens the hindlimb extensor muscles (Drum et al, 2015), notably the hamstrings and gluteals, and also the core musculature. This exercise is ideally performed 10 times (it may be necessary to build up to this if the patient initially shows signs of fatigue), twice daily.
- Rhythmical stabilisation — assists in strengthening the core and quadriceps muscles (Drum et al, 2015). With the patient standing squarely, the therapist uses a point of control, such as the inguinal region or the handle of the patient's harness, to shift the patient's bodyweight forward and back, and/or from side to side for up to 2 minutes, twice daily.
- Gentle balance exercises — lifting the unaffected hindlimb for 30 seconds, twice daily, to encourage weight bearing and loading through the affected limb.
- Baiting exercises — moving a biscuit from the front of the patient's nose to the left hip 10 times, then repeating the exercise on the right side, twice daily.
Weeks 4–16
From 4 weeks to 4 months post injury, the main goal of rehabilitation is continued strengthening of the affected limb. Exercise should be increased gradually until 20–30 minutes of lead exercise twice daily is achieved. This should then be progressed to include the introduction of gentle slopes, then off-lead exercise, starting with 5 minutes (Prydie and Hewitt, 2015). This should be coupled with continued weekly laser and hydrotherapy treatment, and NSAIDs for pain management as required. The therapeutic exercises described above should be increased by 50%.
From 4–6 months a gradual return to normal function should be initiated, beginning with short periods of play, longer periods of off-lead exercise, and the introduction of steeper incline walking (Prydie and Hewitt, 2015).
Conclusion
Despite many studies demonstrating that surgery is likely to deliver the best outcome for most patients (Alveraz, 2011), conservative management remains a viable option for some patients, as long as correct attention is given to case selection. As per the results of the 1984 study on non-surgical management, the author's experience is that the majority of small patients respond well to conservative management, particularly where rehabilitation therapies and sufficient analgesia are included in the treatment plan. The exception would be patients with concurrent meniscal injury, and possibly certain breeds or individuals with a steep tibial plateau angle (Aertsens et al, 2015). More studies are warranted on the relationship between the tibial plateau angle and the best treatment option, as the ability to measure this angle at diagnosis, and advise owners which form of management is likely to have the best outcome would be extremely advantageous to the veterinary team.
As with all patients referred for rehabilitation, it is important that the therapist works in conjunction with the veterinary/orthopaedic surgeon to ensure that patients not progressing as expected be represented for examination/further investigation, so that the treatment options can be re-evaluated if necessary. This is of particular importance in patients receiving conservative management for cruciate disease, as there is often another important treatment option in the form of surgical management. This will be discussed in detail in part two.
Key Points
- Given the prevalent nature of cruciate disease, it should be ruled out in every case of hind limb lameness.
- Diagnosis is achieved through thorough clinical examination paired with radiographs.
- Treatment options include non-surgical (conservative) and surgical options.
- Conservative management is often best suited to small patients under 15 kg.
- If considering conservative management, rehabilitation therapies can be hugely beneficial to the patient both to help manage discomfort and achieve a full return to function.