Cranial cruciate ligament (CrCL) insufficiency is a degenerative condition which causes instability in the stifle (knee) joint. It is a common cause of hind limb lameness and osteoarthritis in dogs worldwide.

The treatments for CrCL insufficiency include conservative management (physical therapy, exercise, nutrition, massage, acupuncture) which may improve function. Surgical management aims to address joint instability through a range of techniques including tibial plateau levelling osteotomy, extra capsular suture stabilization, fibular head transposition and intracapsular ligament replacement.

How does a cruciate ligament injury affect the dog’s gait?

A recent study sought to identify the specific changes in a dog’s movement that an injured cranial cruciate ligament causes, in an attempt to more accurately tailor management and treatment protocols. The study hypothesized that during a walking gait the following would be observed in the affected limb:

• Increased femorotibial flexion. (Femur is the large thigh bone. In the dog’s lower hind leg, there are two bones. The tibia is the bone closest to the dog’s head.)
• Greater cranial (forward) movement of the tibia.
• Greater internal rotation of the tibia.

The study took fluoroscopic images and computed tomographic (CT) scans of the dog’s hind limb joints while they walked on a treadmill. From these images and scans, the research team created 3D models of the dogs’ femur and tibia throughout the gait cycle. For both, the stance and swing phase of the gait, 101 data points were collected – 202 data points in total. Every 10th data point was used to allow averaging between dogs.

Control kinematic data was also collected from the contralateral limb. All dogs in the study had undergone a TPLO (Tibial plateau levelling osteotomy) on the contralateral limb, six months prior to the control data being collected.

18 dogs were included in the study: 11 desexed females and 7 desexed males. The mean age was 6.7 years old and mean body weight 30.3kg.

Within the study group, some of the dogs had degeneration in the stifle joint which may influence the results. Degenerative conditions that were observed were as follows:

• 9 dogs have mild osteoarthritis and 9 dogs moderate osteoarthritis in affected stifle.
• 10 dogs no abnormalities in contralateral stifle. 8 dogs mild osteoarthritis in contralateral stifle.
• 5 dogs mild to moderate osteoarthritis in contralateral coxofemeral joint.
• 8 dogs meniscal pathology identified.
• 9 dogs mild osteoarthritis in tarsus joint but with no pain or loss of range of motion.

Results

Flexion / extension angle

The stifle range of motion over 11 data points indicated that the joint angles of the control joint during the stance phase of the walk were 137 and 147 degrees. While the joint with CrCL insufficiency was held at greater flexion recording angles of 124 and 130 degrees.

Similarly during the swing phase of the gait, the control joint angles were 104 and 146 and the affected joint was 95 and 130 degrees.

Craniolateral translation

Carniolateral translation is the distance between the femoral origin of the cranial cruciate ligament and the tibial insertion. The range of craniocaudal (forward and backward) motion represents the maximum change in distance between the origin and insertion of the ligament throughout the gait.

In the control joint, the mean maximum movement was 1.6mm, while the mean distance for the affected joint was 8.6 mm.

Cranial tibial subluxation

Cranial tibial subluxation is the craniolateral distance between the origin and insertion of the ligament through the gait cycle. In the affected joints, there was significant subluxation with the maximum during the stance phase when the mean was 9.7mm compared to 2.1mm during the mid-swing phase.

Internal / external rotation

Internal / external rotation is the difference between the maximum and minimum axial angular offsets within the joint through the gait cycle. In both the affected and control limb, similar angles were observed, however there were significant differences in the timing of the rotation in the joints.

In the early stage of the stance phase, both stifles were at maximum rotation. By the mid-swing phase the control joint had reached maximum internal rotation while this did not occur with the CrCL insufficient joints until the mid-stance phase. This indicates that for much of the stance phase the affected stifles are abnormally rotated.

Discussion

The study found profound disturbances in the gait cycle for dogs with cranial cruciate ligament insufficiency. The affected joint was held at a greater flexion than the control stifle which may be ascribed to:

• Pain and the presence of fluid in the stifle joint.
• Changes in the activity of surrounding muscles including the quadriceps, gastrocnemius and hamstring group.
• As a way to mitigate cranial tibial subluxation.

Maximum cranial tibial subluxation (movement of tibia forward) was observed during the mid-stance phase. During the mid-stance, the gastrocnemius and quadriceps are engaged to support the dog’s weight and extend the stifle joint. The quadriceps exerts a cranial force on the tibia while the gastrocnemius exerts a caudal force on the femur. The combination of muscle activity may produce cranial tibial thrust during this part of the gait cycle.

While there is cranial tibial subluxation during the swing phase, it is less significant than during the stance phase. It is thought that this may be due to the joint being held in greater flexion perhaps due to fluid in the joint, meniscal degeneration or the osseous structure of the joint which restricts it from returning to a “normal” position. The greater angles of flexion in the stifle may also be due to the contraction of the gastrocnemius during the swing phase to extend the hock.

Finally, during the stance phase in joints with cranial cruciate ligament insufficiency, internal tibial rotation coincides with cranial tibial subluxation. At this stage of the gait cycle, the collateral ligaments compensate for the insufficiency in the cranial ligament. The lateral collateral ligament is not as taut as the medial ligament therefore there is greater possibility for cranial, as opposed to medially translation in the joint. Additionally, the medial meniscus aids in resisting cranial tibial subluxation and provides craniocaudal stability within the joint.

This study has highlighted that:

• Surgical and conservative interventions in dogs with cranial cruciate ligament insufficiency need to address joint instability caused by craniocaudal translation and axial rotation of the tibia.
• Muscle activity imbalance particularly in the quadriceps, gastrocnemius and hamstring muscle group may affect the stability of the stifle joint. Therapeutic exercise, remedial massage and hydrotherapy may be effective in restoring normal muscle function.
• Dogs with cranial cruciate ligament insufficiency have a significantly deviated gait. When dogs’ movement is abnormal it causes weight shifting leading to overloading other joints and soft tissues. This results in secondary areas of pain. Conservation treatments such as remedial massage, hydrotherapy, exercise and diet may address pain and reduce lameness.

Increasingly cranial cruciate ligament insufficiency is being seen as a degenerative condition with potential links to inflammatory conditions. For more information please see: https://www.fullstride.com.au/blog/how-to-prevent-cruciate-ligament-damage-in-dogs

Full Stride provides remedial massage treatments to help address pain and restore mobility.

Until next time, enjoy your dogs.

Source:

Tinga,S, Kim, S.E, Banks, S.A, Jones, S.C, Park, B.H, Pozzi, A, Lewis, D.D. 2018 “Femorotibial kinematics in dogs with cranial cruciate ligament insufficiency: a three dimensional in-vivo fluoroscopic analysis during walking”, BMC Veterinary Research 14:85 (2018)