ABSTRACT: Inside the knee joint are two major ligaments: the cranial cruciate ligament (CrCL) and the caudal cruciate ligament (CaCL). The CrCL is frequently ruptured in severe twisting injuries of the knee. Surgical stabilisation is indicated to reduce the joint instability and associated degenerative changes. Many different surgical techniques are used to repair a CrCL: surgical ligament replacement; mechanical osteotomy procedures and, in severe or complicated cases, a total knee replacement (TKR) may be necessary. Physiotherapy can be helpful before and after surgery in order to re-establish muscle strength and mobility in these cases.


The stifle joint contains two major ligaments: the cranial cruciate ligament (CrCL) and the caudal cruciate ligament (CaCL). These cross in the centre of the joint and control cranial and caudal motion (Figure 1).

Figure 1: Anatomy of cruciate ligaments

The CrCL is a band of connective tissue that connects the femur and the tibia and stabilises the stifle. However, it is frequently ruptured in severe twisting injuries of the stifle.1

Ligaments are located around joints to give them more support, to reduce inappropriate range of movement and to reduce lateral twisting motion. Their lack of contractile ability means that they have to work with the muscles within narrow limitations. Damage to a ligament can lead to instability in a joint and surgery may be required to repair it.

The bones that meet at the stifle joint are the femur and the tibia, whilst the patella is located on the cranial aspect of the joint within the trochlear groove. Cartilage covers the articular surfaces of the joint and allows these to glide smoothly upon each other.

The patellar tendon connects the patella to the upper part of the tibia. Part of this tendon may used in reconstructing a torn CrCL.2

Clinical signs and diagnosis

Clinical signs of a CrCLR may involve: low-grade lameness that is exacerbated by exercise to non-weight bearing, stifle joint effusion, quadriceps muscle atrophy, medial soft tissue thickening, pain, a positive cranial draw test (cranial displacement of the tibia relative to the femur), a positive cranial tibial thrust test (displacement of the tibia), crepitus, altered stifle range of movement; and radiographs may demonstrate the presence of osteophytes on the medial and lateral trochlear ridges and distal poles of the patella and fabellae.

Gait abnormalities may be detected in large breeds; however, in smaller breeds the gait is usually normal.1

Physical examination may show: muscle wastage around the thigh area, tenderness around the gastrocnemius and the cranial quadriceps muscles, periarticular fibrosis, decreased extension of the stifle, tense caudal spine muscles, and pain at the lumbosacral area.3

Diagnostic athroscopy, the introduction of an arthroscope into the stifle joint, may be implemented to diagnose a cruciate ligament rupture4 and radiographic evaluation of the stifle joint can be an aid in confirming the diagnosis – cruciate injury leads to the production of joint effusion and fibrous tissue. Computed tomography (CT) and magnetic resonance imaging (MRI) may also be required in more complex cases.

Rupture of the CrCL and the subsequent joint instability will lead to progressive osteoarthritis (OA) and surgical stabilisation is indicated to reduce the muscle atrophy and the degree of degenerative change in the joint.

Surgical techniques

Many different surgical techniques are used to repair a CrCLR: surgical ligament replacement; mechanical osteotomy procedures and, in severe or complicated cases, a total knee replacement (TKR) may be necessary.

More commonly performed surgical techniques include extracapsular stabilisation, where synthetic material or body tissue is used to replicate the CrCL, leading to extracapsular stability, and the abolition of the cranial draw motion by preventing the tibia from moving cranially in relation to the femur.

Mechanical osteotomy procedures – including the tibial plateau levelling osteotomy (TPLO) and the tibial tuberosity advancement (TTA) use the theory that during weight-bearing activities the cranial draw movement is restricted by two different factors: biomechanical forces and active muscle contraction. These act to stabilise the joint during mobilisation.

The healthy stifle joint has a tibial plateau that is angled caudally, but when there is a rupture the femoral condyle is no longer restricted by the CrCL and so it rolls down this angled bone surface leading to a cranial displacement of the tibia relative to the femur. The idea behind these osteotomy procedures is to abolish cranial tibial thrust.

During the TPLO operation, an osteotomy of the proximal tibia is carried out. This allows rotation of the tibial plateau so that it is almost level. This newly shaped bone is maintained in position with screws and a purpose-designed bone plate. This reduces the shear forces which act on the surfaces of the tibia and femur, which in turn produces more compressive forces and prevents the cranial tibial thrust occurring during normal activities (Figure 2).

Figure 2: Postoperative radiograph following a TPLO procedure

During tibial tuberosity advancement (TTA), a transverse osteotomy is performed behind the tibial tuberosity, allowing the tibia to be advanced to its new position, perpendicular between the tibial plateau slope and patellar tendon, resulting in a stable joint (Figure 3).

Figure 3:. Postoperative radiograph following a TTA procedure   

Physiotherapy aims and equipment

Physiotherapy can be helpful before and after surgery, in order to re-establish muscle strength and mobility. Studies suggest that muscle atrophy can be palpated straight afte
r surgery and can be observed within a few weeks postoperatively. Muscles involved include: quadriceps femoris, biceps femoris, semimembranosus and semitendinosus and strengthening exercises should tatget these muscle groups.5

Techniques used to prevent muscle atrophy include neuromuscular electrostimulation (NMES), which can be used following surgery, if appropriate. The muscles will fatigue quickly, so NMES should be used for short periods of a few minutes initially and built up progressively.

Increasing range of movement (ROM) in the affected area is an important aim of physiotherapy. This can be done by carrying out passive range of movement exercises, which should begin when the animal is recovering from surgery, if appropriate. To prevent continuing muscle atrophy, blood flow to the affected area can be increased with massage, as well as the use of ROM exercises.

The prevention of muscle atrophy and the reduction of adhesions and scar tissue are important aims of physiotherapy. Mobilising the affected area – as well as massage of surrounding soft tissues as soon after surgery as appropriate – will also aid the prevention of adhesions and will soften scar tissue.  

Postoperative instructions and rehabilitation protocols should be checked with the veterinary surgeon as they will vary with different surgeons and will depend on the surgery carried out. Cryotherapy is indicated for postoperative pain relief and reduction of inflammation. The effects of cryotherapy include: vasoconstriction, reduced metabolism at a cellular level, pain relief and a reduction in muscle spasms. Ice and cold packs are normally used for 10 to 25 minutes, depending on the individual and desired effect.

After surgery, cryotherapy can be used three to six times a day. Cryotherapy can be administered to the involved joints after passive ROM exercise or exercise training in the later stages of rehabilitation; and in the case of acute arthritis, it can be applied two to three times daily.3

The long-term aims of physiotherapy include a normal ROM for the individual animal. This is done by gradually increasing use of the limb and continued exercises aimed at re-establishing the patients normal ROM. Another long term aim is to get the animal back to normal weight bearing and exercises Postoperative instructions and   as they will vary with different can be used to promote this, including ‘rocking’ sit to stands, ‘dancing’ and physiotherapy balls. 

It is important to maintain the strength of the surrounding tissues by continuing with NMES until the muscles can maintain themselves through exercise. To prevent deterioration of the joint, exercises should be undertaken to maintain muscle strength and tone. These include: regular hydrotherapy and physiotherapy visits, walking up and down hills, walking on different surfaces such as long grass which will encourage an increased ROM; whilst slow jogging and walking in figure-of-eights or circles will aid proprioception and strength (Figure 4).

Figure 4: Use of a 'theraball· to promote weight bearing whilst challenging proprioception

Dietary management should be employed to prevent the patient becoming overweight. Its environment should also be monitored to ensure that there are no slippery surfaces, that the dog has a soft, warm bed, and that ideally it is not exposed to acute movements such as walking up and down stairs.1 


Sian Norris BSc (Hons) RVN Dip Animal Physiotherapy

Sian graduated from the University of Reading in 2001 with a Degree in Animal Science. During her spare time at university, she worked as a veterinary nurse and after graduating went on to gain her qualification as a Registered Veterinary Nurse in 2004. Sian has most recently completed a Diploma in Animal Physiotherapy and currently works as a ward rehabilitation co-ordinator at an orthopaedic referral centre in Surrey.

To cite this article use either

DOI: 10.1111/j.2045-0648.2012.00152.x or Veterinary Nursing Journal Vol 27 pp 91 -94


1.   GROSS. D. M. [2002] Canine Physical Therapy. Orthopaedic Physical Therapy. Connecticut. Wizard of Paws.

2.   MILLIS, D. L, LEVINE. D.. and TAYLOR. R. A. [2004], Canine rehabilitation & physical therapy. St Louis, Mo. Saunders

3.   BOCKSTAHLER. B.. LEVINE. D„ MILLIS. D L.. and WANDREY. S. O.[2004]. Essential facts of physiotherapy in dogs and cats, rehabilitation and pain management: a reference guide with DVD. Babenhausen. BE Vet Verlag.

4.   TURNER. T. [1990]. Veterinary notes for dog owners. London. Popular Dogs.

5.   MILLIS. D. L. LEVINE, D„ MYNATT, T.. and WEIGEL, J. P. (2000). Changes in muscle mass following transection of the cranial cruciate ligament and immediate stifle stabilisation. Presented at the 27th Annual Conference of the Veterinary Orthopaedic Society, March 4-10, 2000, Val d'lsere, France.

Further reading

SHEALY. P. M. Surgical management of cranial cruciate insufficient dog utilising TPLO. Available from http://my.vetmatrixbase.com/vss.org/ custom_content/c_194651_tplo_information.html 

http://www.fitzpatrickreferrals.co.uk/our-services/surgery/conditions/cranial-cruciate- ligament-injury

Veterinary Nursing Journal • VOL 27 • March 2012 •