I understand your concerns. Please clarify if "back" cruciate ligament refers to the caudal cruciate ligament. The majority of dogs with caudal cruciate ligament tears return to full function with medical therapy alone. For cranial cruciate ligament tears, however, it's important to recognize that ~50% of small (<15 kg) dogs and most cats, but only ~20% of larger dogs such as Bella return to full function with conservative (nonsurgical) therapy. By contrast, all of the surgical treatments listed below have a reported success rate of ~85% for patients of all sizes. Arthritis arises within days of injury and an unstable stifle (knee) will quickly become osteoarthritic necessitating a lifetime of nonsteroidal antiiflammatory drugs and neutraceuticals. The expensive TPLO is not essential but does appear to return my patient to full function more quickly than less expensive prosthetic techniques. Here's a full synopsis of cruciate injury for you taken from Clinical Veterinary Advisor, 3rd Ed., Cote', 2015... Partial or complete tearing of the cranial cruciate ligament (CrCL), causing stifle instability; a very common condition in dogs and an uncommon condition in cats. Isolated caudal cruciate ligament tears are rare. Multiple ligamentous disruptions of the stifle are uncommon traumatic injuries of both dogs and cats.SynonymsAnterior cruciate ligament (ACL) ruptureFor multiple ligamentous disruption: stifle derangement, stifle luxationEpidemiologySpecies, Age, SexSeen in dogs, and less frequently in cats, of all agesGenetics and Breed PredispositionDogs: more common in large breeds, especially rottweilers, Labrador retrievers, Newfoundlands, Staffordshire terriers. Genetic predisposition has been demonstrated in Newfoundlands and boxersCats: not known to be a heritable problemRisk FactorsUnderlying systemic disease: hyperadrenocorticism, autoimmune disease, cutaneous astheniaOverweight conditionOvariohysterectomyAssociated DisordersPatellar instabilityMeniscal injuryOsteoarthritisImmune-mediated arthritisClinical PresentationDisease Forms/SubtypesTraumatic CrCL tearsDegenerative CrCL tearsAvulsion of the insertion of the CrCL: usually in immature dogsInjury to the medial meniscus: often accompanies CrCL ruptureIsolated caudal cruciate tears (rare)Multiple ligamentous injuryHistory, Chief ComplaintVariable lameness of one or both hindlimbs; onset acute or progressiveAffected hindlimb may be held up or off-weighted when animal is standing.Lameness may worsen with exercise and improve with rest.Physical Exam FindingsUnilateral or bilateral hindlimb lameness; affected limb may be held up in acute injuries, will be weight-bearing with more chronic afflictionAffected stifles are externally rotated and more flexed than normal when walking Stifle joint effusion and thickening of joint capsule, often most pronounced over medial aspect of proximal tibia (medial buttress formation)Asymmetrical sitting position with one stifle abductedCranial drawer sign, cranial tibial thrust may or may not be elicited.Meniscal clicking may be present during joint manipulation.With caudal cruciate rupture, the tibia can be caudally displaced relative to the femur (caudal drawer sign).With multiple ligamentous injury, both cranial and caudal drawer sign as well as mediolateral instability can be elicited; stifle may be obviously luxated.Etiology and PathophysiologyBiomechanical instability of the stifle joint results from an imbalance of forces necessary to control the cranial tibial thrust, excessive internal rotation, and hyperextension of the stifle usually limited by an intact cranial cruciate ligament.In dogs, CrCL rupture is usually due to degeneration rather than direct trauma. The cause of this degeneration is unknown: conformation problems, collagen abnormalities, immune disease, and low-grade bacterial infection may play a role.In cats, and in both species with multiple ligamentous injury, direct trauma is usually the cause. DiagnosisDiagnostic OverviewDiagnosis is usually based on presence of the characteristic hindlimb lameness combined with evidence of stifle effusion on physical examination and radiographs. Absence of pain on manipulation, of cranial drawer sign, or of cranial tibial thrust doesnot rule out cranial cruciate rupture as the source of the lameness.Differential DiagnosisPatellar luxationLumbosacral diseaseHip dysplasia or osteoarthritisIliopsoas strainBone/joint neoplasiaOsteochondrosis of the lateral femoral condyleInflammatory arthritisCaudal cruciate or collateral ligament injury (uncommon)Long digital extensor tendon avulsion (uncommon)Isolated meniscal injury (boxers almost exclusively)Initial DatabaseRickettsial and/or fungal titers (based on geography)Palpation of stifle joints for instability; this may require sedation:Cranial drawer sign: manual cranial displacement of tibia relative to femurTibial compression test: cranial tibial translation or thrust (cranial movement of tibial tuberosity as hock is flexed)Lateral and craniocaudal stifle radiographsMedium to large dogs: joint effusion almost always is present; degenerative changes evident after 3 weeksSmall dogs, and cats: joint effusion may be minimal; tibia often cranially displaced relative to femur (“static drawer”)Measurements such as tibial plateau slope angle are made for planning when an osteotomy technique is chosen for repair.Caudal cruciate rupture: there may be an avulsed fragment over the caudal tibial plateau; tibia may be caudally displaced relative to femurMultiple ligamentous injuries: stifle often luxated or abnormally positionedAdvanced or Confirmatory TestingArthrocentesis (to eliminate inflammatory arthritides as causes): see p. 1100Arthroscopy or arthrotomy (the most common way to confirm diagnosis)Magnetic resonance imagingTreatment Overview≈50% of small (<15 kg) dogs and most cats, but only ≈20% of larger dogs, return to full function with conservative (nonsurgical) therapy. By contrast, all of the surgical treatments listed below have a reported success rate of ≈85% for patients of all sizes.Surgical management usually involves inspection (and debridement or release if necessary) of menisci, combined with a stabilization technique. Stabilization techniques involve either creation of a structure (“prosthetic ligament”) to mimic the function of the CrCL, or osteotomy to change the geometry of the stifle so there is minimal cranial tibial translation when the limb is bearing weight.Success rates are similar for prosthetic ligament and osteotomy (TPLO, TTA, TTO) repairs. Return to full weight bearing is usually faster with osteotomy techniques. Cats and small dogs are most commonly treated with prosthetic ligament techniques.Acute General TreatmentMedical management:Physical rehabilitationControlled leash walksSit-to-stand exercisesSwimming, water treadmill workNonsteroidal antiinflammatory drugs (NSAIDs):Carprofen 2 mg/kg PO q 12h; orEtodolac 10-15 mg/kg PO q 24h; orDeracoxib 1-2 mg/kg PO q 24h (may use 3-4 mg/kg PO q 24h for first 7 days only); orMeloxicam 0.1 mg/kg PO q 24h; orTepoxalin 10 mg/kg PO q 24hSurgical stabilization of the stifle (CrCL tear):Intra-articular fascia lata, patellar tendon, or hamstring autogenous graft: aims to replace missing CrCL's functionExtracapsular suture stabilization (femoral condyle or fabella to tibia): limits cranial motion and internal rotation. There are a number of variations on this theme.Fibular head transposition: advances the insertion of the lateral collateral ligament so it can limit cranial drawer and internal rotation (less commonly used these days)Tibial plateau leveling osteotomy (TPLO): neutralizes cranial tibial thrust by changing tibial plateau angle and transferring stress from the absent CrCL to the intact caudal cruciate ligamentTibial tuberosity advancement (TTA): neutralizes cranial tibial thrust by making the pull of the patellar tendon perpendicular to the tibial plateau when the knee is bearing weightTriple tibial osteotomy (TTO): simultaneously reduces tibial plateau slope and slightly advances the tibial tuberosity, making it something like a hybrid of TPLO and TTAPinning or wiring of avulsion injuries to reattach ligament origin or insertion can be done in young dogs with large avulsion fragments.Treatment of meniscal injury:Medial meniscectomy (partial or complete)Medial meniscal release (has an effect similar to meniscectomy, sometimes done prophylactically)Treatment of caudal cruciate injury:In almost all cases, conservative therapy suffices for return to full function.Suture or fascial imbrication can be used in persistently lame dogs.Treatment of multiple ligamentous injury:Debride torn menisci.Extracapsular sutures to replace function of caudal cruciate, medial (occasionally lateral) collateral, and cranial cruciate ligamentsIn cats, a transarticular pin can be used to stabilize the stifle for 10-21 days, after which the pin is removed and fibrosis holds things in place.Chronic TreatmentManagement includes the same treatments as in acute cases, but more long-term medical management of osteoarthritis may be required. Success rates are similar for surgical treatment of acute and chronic cranial cruciate injuries.NSAIDs as listed previouslyPhysical rehabilitationDisease-modifying osteoarthritis agents may be helpful, including:Polysulfated glycosaminoglycan 5 mg/kg IM once weekly × 4-6 weeks; orPentosan polysulfate 3 mg/kg SQ once weekly; orOral formulations (glucosamine, chondroitin sulfate, avocado soy unsaponifiables): according to formulation/labeled instructionsFor animals with end-stage osteoarthritis (rare with cruciate disease), total stifle replacement can be considered.Nutrition/DietWeight control helps alleviate lameness due to osteoarthritis.Behavior/ExerciseMost dogs and cats can return to full function after recovery from surgical treatment of cruciate disease.Possible ComplicationsMedical management:Gastrointestinal, hepatic, renal, or other systemic reactions from NSAID therapyContinued lameness; progression of degenerative joint diseaseSurgical management:Suture breakage, stretch, or slippageFracture or implant failureProgression of degenerative joint diseasePostoperative meniscal injury:Damage not recognized at surgeryShear forces not neutralizedInfectionRecommended MonitoringBasic laboratory monitoring of patients on NSAID therapyWeight loss, exercise levels (rehabilitation), and clinical signs as dictated by the patientRadiographic monitoring of healing of osteotomies (usually at 6 and 10 weeks after surgery), and of any repair if clinical signs worsen Prognosis & OutcomeLong-term function for patients that have undergone a reconstructive procedure is good. Published assessments of most techniques in the past 25 years describe improvement in 80%-90% of dogs after surgery, regardless of methodology.Prognosis after surgery is not affected by whether or not meniscectomy has been necessary, or by degree of osteoarthritis evident on preoperative radiographs.The majority of dogs with caudal cruciate ligament tears return to full function with medical therapy.Prognosis for surgically treated multiple ligamentous injury is similarly good: about 80% of animals return to previous level of performance.Postoperative rehabilitation is critical for full recovery. Pearls & ConsiderationsCommentsBilateral lameness may be difficult to recognize and is often confused with neurologic disease.Injury of the contralateral cranial cruciate ligament occurs in 40%-50% of canine patients. No measures have yet been identified to prevent this from occurring.In one arthroscopic study of partial CrCL injury, TPLO stopped the progression of further ligament rupture in six of seven dogs.Editor's note: Practitioners should consider consultation and referral with an orthopedic surgeon; selection of the “best” procedure continues to be controversial among specialists.PreventionNo reliable preventive measures have yet been identified. As several recent studies have implicated ovariohysterectomy as a risk factor for CrCL rupture, this might be a point to discuss with owners of puppies intended for high-performance work.Maintaining lean body weight may be beneficial.