Management of a Rock Climber’s Unilateral Squat and Knee Flexion Deficits 1-Year Post ACL Reconstruction: A Case Report
Abstract
Case Description: A 27-year-old female one-year post-ACL reconstruction (semitendinosus/gracilis graft) presented with limitations to her knee flexion range of motion (130 degrees vs. 140 degrees), semitendinosus peak strength (6.86 kg vs. 4.01 kg), and rate of force production (31.76 kg/s vs. 17.54 kg/s) respectively. The flexion deficit was particularly observable during a unilateral squat assessment and limited her ability to rock climb.
Methods: The climber then underwent a semitendinosus-biased strengthening program. 30-35 lbs of prone knee flexion with medial tibial rotation (3 times weekly for 8 to 12 repetitions at slow velocity). At the end of 8 weeks, the patient’s ACLR knee attained 140 degrees of flexion, a peak strength, and rate of force production of 4.01 kg and 26.11 kg/s respectively. Improvements in these areas occurred despite no post-protocol changes in the hamstring-to-quadricep ratio (.30).
Conclusion: Flexion and unilateral squat limitations can continually persist post-rehabilitation. Addressing flexion range of motion deficits via strengthening the affected semitendinosus site in 8 weeks appeared to restore the patient's functional baseline.
Introduction
A pistol squat requires a high amount of semitendinosis muscle activation, especially during the descending phase. The majority of anterior collateral ligament reconstruction (ACLR ) involves using a semitendinosus and gracilis muscle graft (STG) for the ACL. Notably, this graft leads to significant strength and velocity deficits in the hamstring that can last as long as two years post-surgery. Furthermore, recent systematic reviews indicate that nearly 50% of athletes post ACLR do not return to play one year post-surgery, indicating that current ACLR rehabilitation protocols and return to sport guidelines are lacking in terms of their ability to prepare athletes for their sporting demands after surgery.
Eliassen, Saeterbakken, and van den Tillaar's (2018) seminal study yielded several important insights regarding unilateral squats.
Compared to bilateral squats, unilateral squats have less activation of the rectus femoris, vastus lateralis and medialis, biceps femoris and erector spinae.
In unilateral squats, particularly the pistol squat variation, greater muscle activation is found in semitendinosus, especially during the descending phase.
A pistol squat shifts one’s center of mass forward, resulting in less hip external rotation, slightly more knee abduction, and an overall greater knee adduction moment, thus requiring greater activation of the semitendinosus and vastus medialis.
In regards to rock climbing, a unilateral squat is particularly useful for several moves of leveraging the climber. These moves include a high-foot (where the foot is placed on a hold higher than the high level), a rock-over (where the upper body rolls past the hips and ankle), and a drop knee (where the tibia rotates medially towards the foot to allow for lateral flexion of the trunk facilitating a greater amount of shoulder extension). All these moves require end-range knee flexion and the ability to generate force from this end-range position, making the unilateral squat a very transferable exercise.
Below is a case study describing how objective strength testing for the hamstrings led to an effective rehab program addressing the patient’s deficits.
Case Report
The patient is a 27-year-old female who underwent ACLR with a STG graft. She had been attending physiotherapy for ACLR rehabilitation for 12 months and was recently cleared by her orthopaedic surgeon and physiotherapist to return to sport. The patient, however, reported to the author that she did not feel at her athletic baseline despite being told her range of motion, quadriceps strength, and ACL integrity were adequate for sport. Upon a strength and power of her hamstring muscles, the author found the following deficits on 03/11/2023.
The patient was then prescribed a heavy-slow resistance program described below.
Strength Program:
Frequency: 2-3 times/week
Intensity: 30-35 lbs depending on knee flexion angle and tension
Type: Prone knee bend with bias on semitendinosus (medial rotation of tibia) and time under tension of 5-8 seconds.
Volume: 8 repetitions x 2 sets
After an 8-week program, the patient was able to achieve symmetrical active flexion with her uninjured knee (140 degrees) and a symmetrical pistol squat. Neuromuscular improvements could also be seen in her semitendinosus strength and rate of force development values.
Discussion & Conclusion
Despite many prospective studies describing decreased knee flexor strength as a risk factor for recurrent ACL injury (post ACLR), the assessment of the hamstrings is not formalized within ACL return-to-sport screening. With the sport of rock climbing gaining greater popularity among the general public, clinicians should become aware of the potential pitfalls in ACLR with STGs. This case study highlights a new frontier of ACLR research for rock climbers due to the ubiquitous need for a unilateral squat in climbing.
The need to bias the semitendinosus muscle would imply introducing a new set of exercises different from traditional hamstring exercises used in the ACLR rehab protocol. Theoretically, the issue with this is that the semitendinosus tendon, being grafted, is subject to arthrogenic inhibition post-surgery resulting in the need for the biceps femoris, semimembranosus, and adductor magnus to compensate for its own deficit. Conventionally, hamstring exercises in ACL protocols focus on the proximal hamstring tendon and reverse Nordics, all these bias the three distal tendons potentially equally. The main problem with performing reverse Nordic hamstring exercises is that the exercise involves both limbs. Thus this remains problematic from a rehabilitation perspective if the clinician wants to impose a heavy eccentric load biased towards the semitendinosus fascicle. One accessible solution to this is to prescribe hamstring exercises that isolate and bias the semitendinosus. This can be done through a prone knee bend with a heavy band around the ankle and having tibial external rotation.
Despite the accumulating evidence showing ACLR patients have persistent and significant deficits in their hamstrings and quadriceps compared to the non-surgical limb after the one-year milestone, nearly all ACLR rehabilitation protocols lack specific guidelines or prescriptions after the one-year milestone. Sports such as rock climbing ,which place significant loads on the lower extremity with unilateral moves, (such as the high-step or a heel hook) require a more in-depth protocol specific to these specific deficits to ensure athletes can safely return to climbing with good performance outcomes. This case study highlights the need for clinicians to adopt objective, quantifiable measures in strength and rate of force development for the lower extremity following ACLR rather than traditional means of return-to-sport criteria.
Key Takeaways:
Many athletes are unable to return to sport following ACLR
There is a current gap in the rehab protocols for ACLR patients that needs to be addressed
Standardized objective, quantifiable, and trackable measures for the hamstring muscles should be incorporated into post-surgical assessment of the ACLR patient
Rehab protocols should focus on unilateral exercises for the hamstring muscles with particular attention to the semitendinosis
References
Eliassen, W., Saeterbakken, A. H., & van den Tillaar, R. (2018). Comparison of bilateral and unilateral squat exercises on barbell kinematics and muscle activation. International journal of sports physical therapy, 13(5), 871.
Kellis, E., Galanis, N., & Kofotolis, N. (2019). Hamstring-to-quadriceps ratio in female athletes with a previous hamstring injury, anterior cruciate ligament reconstruction, and controls. Sports, 7(10), 214.
Nielsen, J. L., Arp, K., Villadsen, M. L., Christensen, S. S., & Aagaard, P. (2020). Rate of force development remains reduced in the knee flexors 3 to 9 months after anterior cruciate ligament reconstruction using medial hamstring autografts: a cross-sectional study. The American Journal of Sports Medicine, 48(13), 3214-3223.
Buckthorpe, M., Danelon, F., La Rosa, G., Nanni, G., Stride, M., & Della Villa, F. (2021). Recommendations for hamstring function recovery after ACL reconstruction. Sports Medicine, 51(4), 607-624.
Ardern, C. L., Taylor, N. F., Feller, J. A., & Webster, K. E. (2014). Fifty-five per cent return to competitive sport following anterior cruciate ligament reconstruction surgery: an updated systematic review and meta-analysis including aspects of physical functioning and contextual factors. British journal of sports medicine, 48(21), 1543-1552.
Makihara, Y., Nishino, A., Fukubayashi, T., & Kanamori, A. (2006). Decrease of knee flexion torque in patients with ACL reconstruction: combined analysis of the architecture and function of the knee flexor muscles. Knee Surgery, Sports Traumatology, Arthroscopy, 14, 310-317.
 | A guest post by
|