Author: Kevin B. Rosenbloom, C.Ped, Sports Biomechanist
The knee joint is a complicated, yet highly functional system that not only allows for movements like flexion and extension, but medial and lateral rotation. The following is a summary of its range of motion, brief descriptions of the muscles contributing to the rotational movements and a glance into research about the structure of the knee joint.
Medial and lateral rotation at the knee joint is the inward or outward rotation of the tibia in relation to the femur. This motion also can contribute to the abduction or adduction of the foot. The biceps femoris long and short head muscles are the main contributors to lateral rotation and the sartorius, gracilis and popliteus muscles are the main contributors to medial rotation (Visible Body 2019). However, in order to observe the range of motion (ROM) of the tibial rotation it is recommended to place a patient’s hips and knees into a flexed position first (Mossberg & Smith 1983, Visible Body 2019).
Range of Motion
During an experiment, researchers noted that an increase in rotation is directly affected by an increase in flexion (Mossberg & Smith 1983). However, the literature Mossberg & Smith present reveals this area of research has not been solidified. The authors also mention that there is no determined consensus in whether individuals experience greater, lesser or equal ROMs for medial or lateral rotation. In the study presented by Mossberg & Smith, a sample size taken from a group of female students displayed a mean of 27.8° of lateral rotation with a more flexible individual reaching up to 43° when the knee was flexed at 90°. The study also stated that when a patient’s knee was flexed at 90°, a mean of 12.6° for medial rotation was noted, with a more flexible individual reaching up to 28°.
Automatic Rotation and the Structure of the Knee
Automatic rotation is also an interesting area of discussion. As an individual approaches terminal knee extension, compulsory movements such as medial rotation of the femur and lateral rotation of the tibia appear (Fuss 1992). Fuss’ study described the reasons for this occurrence being the origins, attachments and structures of the anterior and posterior cruciate ligaments (ACL, PCL) and the anterior curvature of the medial femoral condyle.
Figure 1. Knee Joint Sketch (Right): a. Posterior view of the dislocated knee. b. View of sagittal cross-section of dislocated knee. c. Inferior view of femoral articular surface (above) & Superior view of tibial articular surface (below).
Knee Rotator Muscles
Because all of the muscles have been described in previous summaries, this article will offer links to the locations of their descriptions. However, it is recommended to observe the sketches below to observe their placements and bodies. There will also be a brief written overview of their origins, insertion and additional actions (if applicable) for ease of study.
Muscle Overview - Knee Rotators
Figure 2. Sketch of Knee Lateral Rotators (Right), Posterior View.
Figure 3. Sketch of Knee Medial Rotators (Right), Posterior View.
Biceps femoris long 
Biceps femoris short 
References & Works Cited
Fuss, F. K. 1989. “Anatomy of the Cruciate Ligaments and Their Function in Extension and Flexion of the Human Knee Joint,” American Journal of Anatomy 184: 165-176. https://doi.org/10.1002/aja.1001840208.
Fuss, F. K. 1992. “Principles and mechanisms of automatic rotation during terminal extension in the human knee joint,” Journal of Anatomy 180: 297-304. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1259676/.
Gray, H. 1918. Anatomy of the Human Body, 20th Ed. Lead & Febiger. Philadelphia & New York, USA. 251, 253-258, 339-342, 482-485.
Mossberg, K. A., Smith, L. K. 1983. “Axial Rotation of the Knee in Women,” Journal of Orthopaedic and Sports Physical Therapy4; 4: 236-240. https://www.jospt.org/doi/pdf/10.2519/jospt.19184.108.40.206.
Visible Body. 2019. “Muscle Premium,” VisibleBody.com. Purchasable Application. Accessed 21 Feb 2019.
Kevin B. Rosenbloom, C.Ped, Sports Biomechanist
Kevin B. Rosenbloom, founder and president of KevinRoot Medical, is a renowned certified pedorthist and sports biomechanist practicing in Santa Monica, CA. With his continuing research on the historical development of foot and ankle pathologies, comparative evolution of lower extremities and the modern environmental impacts on ambulation, he provides advanced biomechanical solutions for his patients and clients.