Recovery and rehabilitation for cruciate ligament disease in dogs

Introduction

Cranial cruciate ligament disease (CCLD) is the most common cause of stifle disease and a frequent cause of unilateral limb lameness in dogs (1). Various surgical procedures have been described and studied to treat the condition over several decades, but there is not a single “one-size fits all” surgical technique for CCLD. Similarly, rehabilitation following CCLD is not uniform, but must be tailored to the surgical procedure, patient and outcome goals. However, early phases of rehabilitation are nearly identical for any given stifle stabilization procedure, with a focus on pain control to encourage early controlled weight bearing. Medium and long-term recovery is influenced by the surgical technique employed, as a biomechanical stabilization procedure (e.g., tibial plateau leveling osteotomy (TPLO), tibial tuberosity advancement (TTA)) requires tissue adaptation at a different rate than extracapsular stabilization. This paper offers a broad overview of the factors for a successful recovery following cruciate injury.

Postoperative control of edema and pain

The focus of initial postoperative rehabilitation following surgical stabilization of the cruciate-deficient stifle is increasing early limb use. This is accomplished by aggressively addressing pain and edema, which in turn decreases muscle atrophy (2). Traditionally, pharmaceutical therapy was the only means used to address postoperative pain in animals, but in the modern era non-pharmacologic methods are equally as important in its management. Edema reduction is a component of pain management strategies, as an edematous limb has increased pain due to skin tightness, poor muscle activation and decreased Range of Motion (ROM). 

Some common methods to address pain and edema immediately postoperatively include electrotherapy, cryotherapy, Passive Range of Motion (PROM), Active Range of Motion (AROM), laser therapy, massage, extracorporeal shockwave therapy (ESWT) and pulsed-electromagnetic field (PEMF) therapy (3,4,5,6,7). Most commonly, rehabilitation to address edema and pain postoperatively begins the morning following surgery. 

Cryotherapy and electrotherapy can be performed immediately prior to PROM to reduce pain before any limb manipulation. Cryotherapy is a staple of edema and pain control, as it has a wide array of physiologic effects that are beneficial to the postoperative patient; these include decreased nerve transduction velocity, decreased muscle spindle firing (which reduces muscle spasms), reduced enzyme activity via tissue cooling, and decreased cytokine concentrations, contributing to a mild anti-inflammatory effect. Cryotherapy is applied for 20-30 minutes two to four times daily for the first three or four days postoperatively, but may continue throughout the recovery period as needed for additional pain control. A thin protective cloth layer, such as a pillowcase or t-shirt, should be used to protect the incision and increase patient comfort during therapy. 

Electrotherapy can be administered concomitantly with cryotherapy, thus reducing treatment times (Figure 1a). Transcutaneous electrical nerve stimulation (TENS) is the protocol of choice for postoperative analgesia, which is achieved utilizing the gate-theory of pain control (6). TENS stimulates large diameter sensory afferent nerves, shutting the “gate” on the nociceptive pain signals. Reduction in pain may occur for several minutes to hours following cessation of treatment, creating a beneficial environment to perform manual techniques such as PROM and early limb-use exercises. Application of electrotherapy pads are oriented around the operative joint (Figure 1b) and intensity is increased to a comfortable level or until muscle fasciculations are noted. Typical treatment duration for electrotherapy is 20-25 minutes once or twice daily. 

PROM exercises

Maintenance and improvement of stifle joint ROM is critical for long-term joint health and early limb use. Capsular fibrosis in cruciate ligament disease particularly limits stifle extension, which in turn affects weight bearing when ambulating. Stifle flexion is more tolerant to restrictions, but in severe cases of joint fibrosis, lack of stifle flexion can affect stride length and ability to sit properly. Initiation of PROM should occur within the first 12-24 hours postoperatively, and since patient comfort is imperative to success, any pain medications should be administered 30-60 minutes prior to manual work. When performing ROM exercises in the immediate postoperative period, careful hand placement will maximize patient comfort. Positioning the hands close to the stifle reduces the fulcrum effect and strain on the joint but be aware of where the hands are in relation to the incision; a broad, gentle touch is key to improving comfort. Avoid pulling or distracting the stifle or limb, as this increases patient discomfort; the focus should be on pushing the distal segment while stabilizing the proximal segment in order to slowly and smoothly flex and extend the stifle joint. 10-15 repetitions two to three times daily of PROM, followed by five repetitions of stretching held for 20-30 seconds, should be performed for the first two weeks following surgery. Continuation of PROM and stretching may be necessary in more severely affected joints, but transition to AROM exercises at the time of suture removal is sufficient if extension is normal or near normal.

The other joints (especially the hip) and soft tissues should not be overlooked when performing PROM and stretching. Hamstring tightness can contribute to reduced stifle extension, and the hip flexors (iliopsoas, tensor fascia latae and sartorius muscles) can refer additional pain to the stifle while limiting hip extension. Massage following PROM of these muscles should also be performed to reduce spasm and tightness. 

Muscle strengthening

Remobilization following cruciate stabilization procedures involves not only the joint capsule, tendons and ligaments but the muscular flexibility and stability of the surrounding thigh and hamstring muscles. Progressive muscle atrophy begins immediately postoperatively and peaks around 2-3 weeks after surgery. Recovery of this muscle mass may not occur until perhaps six weeks or even several months later, thus therapeutic exercise should focus on muscle activation and strengthening during the entire recovery period. Degree and intensity are determined by tissue recovery rates, type of surgery and patient tolerance. Simple leashed walks are the cornerstone of therapeutic exercise in the recovery period and offer excellent low-impact exercise. An abdominal sling is recommended for the first week postoperatively with unilateral disease and at least two weeks for bilateral disease. The sling is intended to prevent slips, falls, explosive movements and jumping, and to provide light support to encourage a proper gait pattern while allowing comfortable weight bearing. It is also important to remember the ergonomics of the individual walking the patient to prevent back and shoulder strain (Figure 2a). Slings should be washable, durable and affordable, and a full body harness may be easier for very large dogs and dogs with bilateral disease (Figure 2b). Most dogs tolerate wearing a full body harness for the duration of the day, but it is recommended to remove it at night while the patient is sleeping. All slings and harnesses should be removed if soiled or wet to prevent skin breakdown and to maintain cleanliness. 

Isometric exercises which activate postural muscles should begin immediately postoperatively and can be accomplished with stretch-and-hold lateral postures for a treat or toy. Advancement to three-legged standing and forelimb-elevated standing should begin at approximately two weeks postoperatively. Sit-to-stand exercises may begin as early as three weeks postoperatively for extracapsular repairs if palpably stable, but should be delayed for biomechanical stabilization repairs until four to five weeks to allow for further remodeling of the patellar ligament due to the patellar desmitis inherent to these techniques (Figure 3) (8). If a dog is unable to sit squarely without abducting the limb, a modified or assisted sit-to-stand should be performed first before progressing to a standard sit-to-stand (Figure 4). Posture is important in all exercises during recovery but is of utmost importance in sit- or down-to-stand exercises. In order to maximize limb use, a platform can minimize a dog using its forelimbs to pull itself forward rather than pushing up with the hindlimbs (Figure 5). Stair climbing, incline walking, land treadmill work (including jogging), walking in reverse, “superman” two-legged standing, weaving, figure 8’s, progressive stride lengthening, cavaletti rails, sit-to-stands facing up or horizontally on an incline, or short “fetches” from a static position are just a few later-stage strength-building exercises. Exercises can be made more challenging by adding unstable surfaces and props (Figure 6). 

Proprioceptive exercises are initiated immediately postoperatively and frequently occur as compound exercises to address both muscle activation and balance. Joint proprioceptors are lost early following injury and surgery, and are the last to return. While there are low-threshold mechanoreceptors embedded within the joint capsule, muscle spindles that signal changes in length of muscles provide the primary information regarding joint position. Thus, proprioceptive exercises must include muscle activity to effectively retrain joint proprioception. Rhythmic stabilization, which involves alternating isometric contractions against resistance without movement, is a key proprioceptive neural facilitation technique that should be started immediately postoperatively. Rhythmic stabilization differs slightly from basic weight shifting; bouncing on an unstable surface or manual compression of the pelvis while standing are two common methods of performing rhythmic stabilization (Figure 7), but this can be very fatiguing, and the patient may only tolerate 60-90 seconds of the motion without a rest. The goal is 5 minutes total per session and may be alternated with simple weight-shifting during a session for patient compliance. The exercise should be repeated 2-3 times daily for the first two to four weeks. Proprioceptive exercises should be continued throughout the entire recovery period, and in later stages proprioceptive input can be accomplished by performing strength exercises on unstable surfaces such as balance disks, peanut balls or other unstable props. For example, sit-to-stands with the forelimbs elevated and the hindlimbs on a balance disk, or standing on two peanut balls while catching a toy, are two advanced later-stage options. 

Advancement of exercise depends on a variety of factors. In addition to a home-based vs. professional outpatient setting, influencing factors such as equipment, inherent dog ability or training level, client willingness or availability, type of surgery, complications, chronicity of disease and patient comorbidities should be considered. Consistent follow-up is also integral for program advancement. In a professional outpatient setting, exercise progression often occurs every 3-7 days or every second or third session. This may involve increasing repetitions, duration or speed when performing the exercises. With home-based programs, advancement tends to be slower, at a rate of every 2-4 weeks as patient contact is less frequent. 

In addition to the special considerations for the patellar ligament remodeling with biomechanical repairs (such as TPLO/TTA), bony healing also limits recovery times and lameness progression. There appears to be a role for laser (9) and shockwave therapy (10,11,12) in the healing of the osteotomy site and patellar ligament remodeling when used early. In cases of delayed healing or non-union, shockwave therapy is the ideal treatment; ESWT specifically stimulates bone morphogenic protein-2 (13), an essential cytokine for promoting osteotomy healing. Additionally, shockwave provides pain relief to support and encourage limb use.

Most of the therapies described above can be started within the first 24 hours post-surgery, with additional exercises commencing anywhere from 5 days to 5 weeks postop. The reader is referred to the literature for a summary of the options and possible timings for their introduction, as these can vary enormously depending on a multiplicity of factors related to the individual patient (14).

Weight management

Weight management and nutrition are also key to successful recovery from cruciate ligament surgery and injury. Obesity is a risk factor for development of cranial cruciate ligament rupture (15). Weight loss often comes at the expense of muscle mass, but can be offset with diet and regular exercise. Low calorie, high protein diets with additional omega-3 fatty acid supplementation are ideal for the cruciate patient, whether being managed surgically or conservatively. While a high omega-3 fatty acid diet alone may be as beneficial as rehabilitation (16), diet and exercise are still superior in maintaining muscle mass. Specifically, underwater treadmill (UWTM) exercise can attenuate the loss of muscle mass in dogs during a standard weight loss program (17). Treadmill protocols can be designed to focus on stifle ROM, muscle strength and endurance while reducing ground impact on the operative limb. Twice weekly UWTM therapy is a standard frequency during the recovery period, but may be increased or decreased based on patient needs and tolerance. However, a minimum of weekly sessions during the critical initial 2–8-week period is recommended to appreciate consistent benefits. Swimming is also useful, but intensity of movements in the water, and entry or exit to the water, are often too risky within the first 3-5 weeks postoperatively. Open water swimming is an excellent mid and late term exercise for cardiovascular fitness, calorie burning and core strength, and sessions should begin with 3-5 minutes of continuous swimming. Fetching in water, where return to solid ground interrupts deep water swimming, may also be suitable, but careful monitoring for increased lameness due to jumping in and out of the water is key. Uncontrolled swimming should not begin until leash restrictions have been lifted.

Non-surgical management of CCLD

Many patients are not candidates for surgical treatment of cruciate ligament tears due to comorbidities or client limitations. It is feasible to manage all states of cruciate disease conservatively, but the owner should be properly educated about expected outcomes and limitations with this option. While some patients are successful without surgery, many can have significant lameness that persists for many months or even indefinitely. It can, however, be reasonable to attempt conservative management for 6-12 weeks and pursue surgery at a later date if non-surgical management is unsuccessful. Exercise restriction should still involve 8-12 weeks of eliminating running, jumping, rough play or tight pivoting, similar to recommendations for a postoperative patient. Therapeutic exercise protocols are not different for the first 8-12 weeks between surgical and non-surgical management, but conservative management progression is slower and requires a minimum of 3-6 months of controlled exercises to allow for maturation of scar tissue and muscle compensation to stabilize the stifle. Use of an orthosis (e.g., a splint or brace) is not a substitute for surgical repair; the goal of orthotic use is to improve proprioceptive feedback and encourage stifle extension, but the device cannot eliminate instability. Regenerative medicine, such as platelet-rich plasma or stem cell therapy, is another treatment choice for conservative management to encourage, and may help reduce synovitis and progression of damage in partial cruciate tears (18). 

Conclusion

A multi-modal approach should be utilized for successful management of cruciate ligament disease. Controlled therapeutic exercise is required of any rehabilitation for cruciate ligament disease, and progression of exercise depends on a wide variety of factors. Non-surgical management is plausible, but surgical treatment provides superior weight bearing and more consistent outcomes long-term. The rehabilitation of cruciate ligament disease is identical in the first 8-12 weeks of the program regardless of treatment, but modifications must be made based on surgical procedure or non-surgical management, chronicity of disease and other individual patient factors. The key to successful rehabilitation of these cases is consistent adherence to the exercise protocol, alongside regular follow-up to allow adjustments based on individual patient response.

References

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