The goniometer, as a fundamental measurement tools in physiotherapy, has played a pivotal role in transforming the field from a manual profession into a scientifically grounded discipline. Its application has enabled the objectification of therapeutic procedures through quantitative assessment of the range of motion, thereby opening the door to systematic evaluation of treatment effectiveness and laying the groundwork for evidence-based practice.

Introduction

Physiotherapy inherently embodies the essential connection with nature and the natural world. Rooted in the Greek words phýsis (nature) and therapeía (treatment or care), the term itself reveals the essence of physiotherapy: healing through natural means. This reflects the original concept of using natural agents (such as movement, heat, water, and light) for treatment and rehabilitation. That is how it all began; however, in the evolution of physiotherapy, one instrument played a crucial role. Before its introduction, a fundamental question arose: how can we prove the effectiveness of what we do? Eventually, this became a necessity. It became essential to explain how we measure the effectiveness or ineffectiveness of physiotherapy—thus, the revolutionary instrument for the physiotherapy profession was born: the goniometer.

Seemingly simple, the goniometer has historically demonstrated its epistemological role in the transformation of physiotherapy from a clinical practice to a scientific discipline. The concept of measurable movement and the goniometer as a paradigmatic instrument laid the groundwork for the scientific validation of physiotherapy. This refers primarily to the movement within the human body. One could say that the goniometer marks the beginning of scientific methodology in physiotherapy. It gives the impression that a transition occurred—from the empirical approaches commonly used in proto-physiotherapy, such as manual massage techniques, toward an active approach in which individuals heal through movement. Physiotherapy, as a practice that uses therapeutic movement for healing, prevention, or enhancement, thus necessitated an active approach—where the patient receives movement as therapy and the therapist employs a structured procedure. This moment created the need for proof of the efficacy of such activity. The possibility of measurement as a scientific foundation was born, with the goniometer representing the development of physiotherapy as a scientific discipline. Chronologically, the emergence, use, development, and presence of the goniometer track the evolution of physiotherapy from a trade to a scientific discipline. As a tool for the quantitative assessment of the range of motion, the goniometer has a long history in biomechanical and clinical application.

The measurement of joint mobility is one of the key components in evaluating a patient’s functional status during the physiotherapeutic process. Standardization of such measurements enables monitoring of therapeutic outcomes, goal setting, and scientific validation of treatments (Norkin & White, 2016).

The Historical Development of the Goniometer

The concept of measuring angles and movements dates back to antiquity, where mathematicians like Euclid developed geometric principles that would later be applied in the sciences (Clarys et al., 1999). The first known use of a primitive version of the modern-day goniometer was by a Dutch physician, mathematician, cartographer and philosopher named Gemma Frisius in 1538. He used it to calculate and record the position of celestial bodies with respect to the earth.

Goniometry originates from two Greek words: gonia, which means angle, and metron, which means to measure. The first known prototypes of instruments for measuring joint angles appeared in the 18th century, coinciding with the development of anatomy and orthopedics as scientific disciplines.

In the 19th century, with the advancement of orthopedic devices and a growing interest in rehabilitation, mechanical goniometers made of metal or wood began to be used. Their rudimentary design featured two arms connected by a rotational axis and engraved scales, enabling precise readings of joint angles (Peterson & Renström, 2001).

The true integration of the goniometer into physiotherapy practice occurred in the early 20th century, as physiotherapy became institutionalised, especially during and after the First World War, when evaluating the functional recovery of wounded soldiers became essential (Licht, 1967).

Standardization and Clinical Application in Physiotherapy

By the mid-20th century, measurement procedures were standardised, especially following the publication of guidelines defining normative values for specific joints (American Academy of Orthopaedic Surgeons, 1965). The goniometer became an indispensable part of physiotherapy documentation, particularly within the framework of objective evaluation using the SOAP model (Browne et al., 2005). Manual goniometry is used to assess both active and passive ranges of motion, with measurement reliability depending on standardised patient positioning, therapist experience, and the construction of the device itself (Riddle et al., 1987).

With technological advancements in the latter half of the 20th and early 21st centuries, digital goniometers, inclinometers, and mobile applications for biomechanical analysis enabled more precise and replicable movement evaluations (Ferriero et al., 2011). The integration of sensor technologies and 3D motion capture systems further expanded the possibilities of goniometry in both research and clinical environments (Cutti et al., 2008). Smartphone-based goniometers, using validated applications, have demonstrated high correlation with traditional tools, enhancing the accessibility and mobility of measurements, especially in outpatient and home-based settings (Tousignant et al., 2015).

Discussion

In the context of physiotherapy’s evolution as a scientific and clinical discipline, it is essential to ask how instruments such as the goniometer contribute to the quantification and validation of therapeutic interventions. The goniometer can be viewed not only as a measuring device but also as a symbol of physiotherapy’s transition from predominantly manual and empirically driven methods to an objectified, measurable, and scientifically verifiable approach.

Can it be said that the goniometer was among the first tools enabling physiotherapists to systematically record and evaluate therapy outcomes? At a time when therapeutic methods relied on experiential knowledge and practical skills, the goniometer introduced a new level of standardisation and comparability. In this regard, it can be seen as one of the pioneers of scientific methodology within the field of physiotherapy. Its role is particularly significant given that scientific verification of the efficacy of rehabilitation methods was long hindered by the lack of measurable data. Goniometric measurements laid the foundation for the development of further evaluation tools and scales that now form the core of modern evidence-based practice.

Thus, one may reasonably hypothesise that the goniometer helped physiotherapy move away from a paradigm based solely on manual and subjective techniques, entering the domain of a measurable, scientifically grounded profession.

Conclusion

The evolution of the goniometer—from a mechanical instrument to sophisticated digital systems—illustrates the progressive professionalisation of physiotherapy and the growing demand for quantitative, reliable, and validated methods of evaluation. This historical review underscores the importance of continually improving measurement tools to optimise clinical practice and scientific research in the field of physiotherapy. In most Central and Eastern European countries, the goniometer can be viewed as an instrument marking the chronology of the development of physiotherapy from practice to a scientific discipline.

References

American Academy of Orthopaedic Surgeons. (1965). Joint Motion: Method of Measuring and Recording. Chicago: AAOS.

Browne RH, Franz JE & Hall JH. (2005). Objectivity in clinical outcome measures: Applications in physical therapy. Journal of Rehabilitation Research and Development, 42(3), 45–52.

Clarys JP, Martin AD & Marfell-Jones MJ. (1999). Anthropometric measurement options for the assessment of physical fitness. Human Kinetics, 10(2), 27–43.

Cutti AG, Ferrari A, Garofalo P, Raggi M, Cappello A & Davalli A. (2008). Outwalk: A protocol for clinical gait analysis based on inertial and magnetic sensors. Medical & Biological Engineering & Computing, 46(12),1121–1132.

Ferriero G, Sartorio F, Foti C, Franchignoni F, Molteni F and Cisari C. (2011). Reliability of a new application for smartphones (DrGoniometer) for elbow angle measurement. British Journal of Sports Medicine, 45(8), 649–651.

Licht S. (1967). History of Physical Therapy. Baltimore: Williams & Wilkins.

Norkin CC & White DJ. (2016). Measurement of Joint Motion: A Guide to Goniometry, 5th ed. Philadelphia: F.A. Davis Company.

Peterson L & Renström P. (2001). Sports Injuries: Their Prevention and Treatment. 3rd ed. London: Martin Dunitz.

Riddle DL, Rothstein JM & Lamb RL. (1987). Goniometric reliability in a clinical setting: Shoulder measurements. Physical Therapy, 67(5), 668–673.

Tousignant M, Moffet H, Boissy P, Corriveau H, Cabana F & Marquis F. (2015). Validity of a smartphone-based goniometer for measuring active knee flexion/extension. Telemedicine and e-Health, 21(8), 650–655.

Dedication

This reflection on the goniometer is dedicated to my esteemed colleague and recent doctoral graduate of Alma Mater Europaea University in Slovenia, Dr. Iva Lončarić Kelečić. I had the honor of mentoring her on a path marked by dedication, knowledge, and vision. As the first PhD in physiotherapy in Croatia, Dr. Lončarić Kelečić did more than defend a dissertation—she defended physiotherapy as a science. Her work and perseverance represent a bridge from profession to scientific discipline, and this text stands as a tribute to the milestone she achieved, with the hope of inspiring future generations who enter the science of physiotherapy through practice and continue to drive it forward.