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Outcomes of anterior cruciate ligament reconstruction from 2 to 20 years post-surgery

Joints in the body are supported by different structures such as joint capsules, muscles, and ligaments. Joints in the legs are designed for both weight-bearing and mobility, and ligaments play a major role in providing stability to the joints. For locomotion the knee is a key joint, as it connects two long-bones in the leg and is supported by a number of strong ligaments. The anterior cruciate ligament (ACL) is one of the ligaments present in the center of the knee [Figure 1], and it plays a major role in guiding mobility and maintaining stability when we walk, run or hop.

Figure 1. Location of anterior cruciate ligament in knee joint.

The anterior cruciate ligament is commonly ruptured during sports. As a treatment option, repair of the ruptured ligament through surgery is advised, and this has become quite a popular approach. Although the ruptured ligament is functionally repaired with a surgery, it is not completely restored to its original condition, and individuals are known to be at high risk of re-injury and early onset of osteoarthritis for a few years following surgery. However, the underlying causes of these post-surgery complications are not well known. I was especially interested in finding out how long it took a repaired knee to regain its normal condition after surgery. Therefore, for my PhD I asked the question “whether physical, psychosocial, biomechanical or knee function-related impairments persist in participants up to 20 years following an ACL reconstruction surgery in New Zealand?”

How did the process start?

My PhD journey began with a need to understand the way knee moves. Therefore, I started searching for published research papers that described the movement pattern of the knee following ACL reconstruction surgery during different tasks, such as walking, running, climbing and going down the stairs. In summary, all of these papers revealed that, when compared to those without injury (a control group), people with ACL surgery were able to walk without any major differences in terms of knee bending angles on the injured side, during most of the tasks. However, this was not the case when I analyzed the knee moments (the torque generated by the muscles, or we can say the bending force from the muscles) during climbing and going down stairs. Here people with ACL surgery were able to generate less knee straightening torque compared to the controls. In a nutshell, everything was not FINE with their knee, even after 3.5 years following surgery. The results of this analysis have been published, and you can find it here.

Connecting the dots…what about the joint movement?

Thinking about the results from the above study, I started wondering if these differences in knee movement pattern persisted in participants over the long-term following surgery. As the above analysis only showed differences when climbing or descending stairs, which is relatively more challenging than walking, I decided to analyze the knee movement pattern of participants on stairs in our laboratory in the School of Physiotherapy (University of Otago). I set up this experiment to measure the knee angles and moments (bending torque or forces) of participants going up and down the stair using 3D cameras and force plates [Figure 2]. Twenty-five participants with surgery, and twenty-six without surgery, volunteered from the community (and I am very grateful for their time and help!).

Figure 2. Camera set up for the motion capture. Gray are the force plates, black outline near the force plates represents the capture volume.

The fascinating finding from my stair study was that the participants with surgery move their knee differently compared to the those without knee surgery. Surprisingly, participant with ACL surgery were able to generate less knee straightening torque compared to the opposite knee and control group. However, when I looked at movement patterns descending the stairs I didn’t find any major differences. This revealed that differences in knee movement pattern may persist up to 10 years following surgery, and become noticeable as physical activity increases.

What about the muscles of the thigh?

Additionally, I wanted to determine the thigh muscles strength of the quadriceps and hamstrings [muscles at the back and front of the thigh] compared to uninjured people. Thigh muscles strength in these 25 participants was measured on an isokinetic dynamometer machine for testing muscle strength. I found that, for the participants with ACL injury, the front thigh muscle group was weak compared to their uninjured side, and also compared to the muscles of uninjured people. 

How about the participants’ physical activity and quality of life after surgery?

To get a deeper understanding about the participants’ life, and about the consequences of ACL reconstruction relative to physical activity, sports, occupation and quality of life, I interviewed ten participants from those who had taken part in the stair study. The results I found were startling, as participants indicated that even after 2-10 years following surgery, they still had hesitancy in weight bearing on the injured side during certain tasks. They shared that there was still something holding them back, which lead to hesitation. They had a fear of re-injury, and they were not confident during certain movements, especially turning and twisting in sports-related tasks.

In summary, what I have found?

Together, these studies showed that the physical impairments and psychological concerns of participants persisted from mid- to long-term (2-20 years) following reconstructive surgery. I also found that participants had changed knee movement pattern, reduced quadriceps strength, had a high fear of re-injury, and had low confidence levels in using their knee during sports. Therefore, I can strongly say that we still need to develop optimum measures to improve the quality of life of patients following ACL reconstruction surgery.


Academic readings:

Kaur, M. (2018). Outcomes of anterior cruciate ligament reconstruction from 2 to 20 years post-surgery: a mixed-method approach (Thesis, Doctor of Philosophy). University of Otago.  Retrieved from

Kaur M., Ribeiro D.C, Theis, J.C., Webster, E.K, Sole. G (July, 2017) Differences in sagittal plane kinematics and kinetics during stair negotiation in participants with Anterior Cruciate Ligament reconstruction compared to control group. International Society of Biomechanics conference, Brisbane, Australia.

Kaur, M, Ribeiro D.C, Theis, J.C., Webster, E.K, Sole. G (2016). Movement patterns of the knee during gait following ACL reconstruction: a systematic review and meta-analysis. Sports Medicine 46.12: 1869-1895. doi: 10.1007/s40279-016-0510-4.

Kaur, M, Ribeiro D.C, Theis, J.C., Webster, E.K, Sole. G (2018). Patients’ perspectives of anterior cruciate ligament reconstruction surgery. Physiotherapy New Zealand Conference, Dunedin, New Zealand. (Abstract book p 65)