Student Name: Jacob Spurr-Romanov

Student Name: Jacob Spurr-Romanov

Student ID: S346909

Subject Code: SPE261

Subject: Functional Anatomy

Topic: Knee Extension through a Back Squat

Date:

Introduction

The squat movement pattern is a fundamental and essential movement that can significantly enhance sports performance, prevent injuries, and support overall physical activity. Throughout human evolution, the knee joint has evolved to efficiently handle forces and loads associated with squatting (Myer et al., 2014). The back squat is closely linked to lower body strength development, improved athletic performance, and injury prevention. (Hirschman & Mller, 2015).

This analysis provides a comprehensive overview of the biomechanics of the knee joint during the transition from flexion to extension. It delves into various aspects, including segment motions from the anatomical position, identification of primary muscle movers, the nature of muscle contractions, the role of neuromuscular control, and essential principles for safe knee movements.

Body

The knee is an intermediate hinge-type synovial joint in the lower limb, facilitating movement between the femur, tibia, and patella. Its articular surfaces include the curved medial and lateral femoral condyles, corresponding to the tibial plateaus. The medial tibial plateau is biconcave, while the lateral is concave on the frontal plane and convex on the sagittal plane. Both femoral condyles are convex in both sagittal and frontal planes. The two tibial surfaces with a double concave curvature in the frontal aspect are separated by the intercondylar eminence. The geometric shape of the condyles is the most important factor for the stability of the knee under loads (Vaienti et al., 2017).

Figure 1:

Normal Anatomy of the Knee

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Note. From Malabar Orthopaedic Clinic, by Prof Stephen McMahon, (n.d), (https://www.hipandkneesurgeonmelbourne.com.au/normal-anatomy-knee-joint.html). Copyright by Prof Stephen McMahon.

The knee is the largest joint in the human body with a very complex anatomy. It is a mobile trochoginglymus (i.e., a pivotal hinge joint), which permits flexion and extension as well as a slight medial and lateral rotation. The Slight medial and lateral rotation is the result of the complex arrangement of ligaments and the minimal movement for hyperextension (Kochhal et al., 2019).

Flexion of the knee is produced by the biceps femoris, semitendinosus, and semimembranosus muscles (hamstring) and extension of the knee is produced by the sartorius and quadriceps femoris group of muscles. Garratt et al, (2004) state that muscle forces and ligaments allow the stable articulate movement of the knee to move an average of around 130. Synovial fluid is expended to reduce friction between articular cartilages of synovial joints during movement. The presence of high molar mass hyaluronan (HA) in this fluid gives it the required viscosity for its function as a lubricant solution. Additionally, aids the supply of oxygen and nutrients within the joint and reduces shock. (Tamer, 2013).

Ligaments

The knee joint consists of four main ligaments that connect the femur (thighbone) to the tibia (shin bone). These ligaments are the Anterior Cruciate Ligament (ACL), which prevents excessive forward movement of the tibia, the Posterior Cruciate Ligament (PCL), which prevents excessive backward movement of the tibia, the Medial Collateral Ligament (MCL), which provides stability against inward forces, and the Lateral Collateral Ligament (LCL), which provides stability against outward forces. Together, these ligaments play a vital role in maintaining the stability and integrity of the knee joint during various activities (Hall, 2022).

Figure 2:

Ligament injuries to the knee

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Note. Comprehensive Orthopaedics, by Comp Ortho, (2017). (https://comportho.com/knee/ligament-injuries-to-the-knee/). Copyright by Comp Ortho.

Muscles

Several pulling muscles are involved increase or decrease the angle of the joint, resulting in the knee moving freely (Comfort et al., 2023). With the individual in a standing position, hips, head and feet in a neutral position, the knees bent to 130, arms knee width apart stabilising a bar is where the analysis of knee extension begins.

Figure 3:

Isometric lowered position of a squat.

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Note. From Strength Cond J. Vol. 36, by Myer et al., (2014).

Figure 4:

The primary movers in knee extension, proximal and distal attachment, primary action about the knee, muscle fibre innervation and nature of contraction.

MUSCLE PROXIMAL ATTACHMENT DISTAL ATTACHMENT PRIMARY ACTION(S) ABOUT THE KNEE INNERVATION NATURE OF CONTRACTION

Rectus femoris Anterior inferior iliac spine (ASIS) Patella Extension Femoral (L2L4) Concentric (Shortening)

Vastus lateralis Greater trochanter and lateral linea aspera Patella Extension Femoral (L2L4) Concentric (Shortening)

Vastus intermedius Anterior femur Patella Extension Femoral (L2L4) Concentric (Shortening)

Vastus medialis Medial linea aspera Patella Extension Femoral (L2L4) Concentric (Shortening)

Semitendinosus Medial ischial tuberosity Proximal medial tibia at pes Flexion, medial rotation Sciatic (L5S2) Eccentric (Lengthening)

Semimembranosus Lateral ischial tuberosity Proximal medial tibia Flexion, medial rotation Sciatic (L5S2) Eccentric (Lengthening)

Biceps femoris Ischial tuberosity (Long head)

Lateral linea aspera(Short head) Posterior lateral condyle of tibia, head of fibula Flexion, lateral rotation Sciatic (L5S2) Eccentric (Lengthening)

Sartorius Anterior superior iliac spine Proximal medial tibia at pes Assists with flexion and lateral rotation of thigh Femoral (L2, L3) Eccentric (Lengthening)

Gracilis Anterior, inferior symphysis pubis Proximal medial tibia at pes Adduction of thigh, flexion of lower leg Obturator (L2, L3) Eccentric (Lengthening)

Popliteus Lateral condyle of the femur Posterior medial tibia Medial rotation, flexion Tibial (L4, L5) Eccentric (Lengthening)

Gastrocnemius Posterior medial and lateral femoral condyles Tuberosity of calcaneus via Achilles tendon Flexion Tibial (S1, S2) Eccentric (Lengthening)

Plantaris Distal posterior femur Tuberosity of calcaneus Flexion Tibial (S1, S2) Eccentric (Lengthening)

Note. From ISE EBook online access for basic biomechanics(Eighth edition). Hall, S, (2022). Copyright by Hall, S.

Figure 5:

Muscles of the upper and lower leg.

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Note. Admin, by Doctor Lib, (n.d). (https://doctorlib.info/anatomy/classic-human-anatomy-motion/8.html). Copyright by Doctor Lib.

Safe Movement Principles

The back squat is an extremely beneficial movement when conducted correctly. Common movement compensations include knee valgus (knock knees), rounding or arching of the lower back, an excessive forward lean of the torso, and overly externally rotating or pronating the feet (Comfort et al.,2017). Myer et al (2014) further outline in greater detail the correct criteria to conduct the back squat, whilst using safe practice.

Figure 5:

A Back Squat

Note. From Strength Cond J, by Myer et al., (2014). Copyright from Myer et al.

Conclusion

This analysis provides a detailed overview of the biomechanics of the knee joint during the movement from flexion to extension. It emphasizes that the knee joint is composed of the femur, patella, tibia, and fibula. The analysis covers segment motions from the anatomical position, identifies primary movers, describes the nature of muscle contractions, explores the role of neuromuscular control, and presents essential principles for safe knee movements. (Garratt et al., 2004).

Hirschmann & Mller (2015) emphasized the significance of back squatting for the general population. They highlighted that it plays a crucial role in improving lower body strength, enhancing athletic performance, and preventing injuries.

References

Comfort, P., & Kasim, P. (2017). Optimizing squat technique. Strength and Conditioning Journal, 29(6), 10-13.

Comfort, P., Haff, G., & Suchomel, T. (2023). National Strength and Conditioning Association position statement on weightlifting for sports performance.J Strength Cond Res, 37(6), 1163-1190. https://doi.org/10.1519/JSC.0000000000004476Comprehensive Orthopaedics. (2017). Ligament injuries to the knee. https://comportho.com/knee/ligament-injuries-to-the-knee/Doctor Lib. (n.d). Classic human anatomy in motion. https://doctorlib.info/anatomy/classic-human-anatomy-motion/8.htmlGarratt, A., Brealey, S., & Gillespie, J. (2004). Patient-assessed health instruments for the knee: a structured review. Oxford Rheumatology, 43(11), 1414-23. https://doi.org/10.1093/rheumatology/keh362Hall, S. (2022).ISE EBook online access for basic biomechanics(Eighth edition). McGraw-Hill Higher Education.

Hall, S. (2018). Basic Biomechanics. McGraw-Hill US Higher Ed ISE. http://ebookcentral.proquest.com/lib/cdu/detail.action?docID=5561467.

Hirschmann, M., & Mller, W. (2015) Complex function of the knee joint: the current understanding of the knee.Knee Surg Sports Traumatol Arthrosc,23, 27802788 https://doi.org/10.1007/s00167-015-3619-3Kochhal, N., Thakur, R., & Gawande, V. (2019) Incidence of anterior cruciate ligament injury in a rural tertiary care hospital. J Family Med Prim Care, 10(12), 4032-4035. https://doi.org/10.4103/jfmpc.jfmpc_812_19Kushner, A., Brent J., Schoenfeld, B., Hugentobler, J., Lloyd, R., Vermeil, A., Chu, A., Harbin, J., McGill, S., & Myer, G. (2015). The back squat part 2: targeted training techniques to correct functional deficits and technical factors that limit performance. Strength Cond J, 37(2), 13-60. https://doi.org/10.1519/SSC.0000000000000130.

Malabar Orthopaedic Clinic. (n.d). Normal anatomy of the knee. https://www.hipandkneesurgeonmelbourne.com.au/normal-anatomy-knee-joint.htmlMyer, G., Kushner, A., Brent, J., Schoenfeld, J., Hugentobler, J., Lloyd, S., Vermeil, A., Chu, A., Harbin, J., & McGill, M. (2014). The back squat: A proposed assessment of functional deficits and technical factors that limit performance. Strength Cond J, 36(6), 4-27. https://doi.org/10.1519/SSC.0000000000000103.

Tamer, M. (2013) Hyaluronan and synovial joint: function, distribution, and healing. Interdiscip Toxicol, 6(3), 111-25. https://doi.org/10.2478/intox-2013-0019.

Vaienti, E., Scita, G., Ceccarelli, F., & Pogliacomi, F. (2017) Understanding the human knee and its relationship to total knee replacement. Acta Biomed, 88(2), 6-16. https://doi.org/10.23750/abm.v88i2-S.6507