--- a
+++ b/Docs/body/leg_tlem2_model.md
@@ -0,0 +1,204 @@
+(tlem2)=
+
+# Twente Lower Extremity Model v.2.2
+
+The Twente lower extremity model version 2 (TLEM2) is a successor to the {doc}`TLEM 1
+model <leg_tlem_model>`. It contains **6 DOF** and **169
+muscles**.
+
+```{raw} html
+<video width="45%" style="display:block; margin: 0 auto;" controls autoplay loop>
+    <source src="../_static/TLEM2_rotating_model.mp4" type="video/mp4">
+Your browser does not support the video tag.
+</video>
+```
+
+
+## Example Configuration
+
+Short example of how to configure the model with the TLEM model, Hill type
+muscle model and only one leg:
+
+:::{seealso}
+:class: margin
+The {doc}`Leg configuration parameters <../bm_config/leg>` for a
+full list of configuration parameters.
+:::
+
+```AnyScriptDoc
+#define BM_LEG_MODEL _LEG_MODEL_TLEM2_
+#define BM_LEG_RIGHT ON
+#define BM_LEG_LEFT OFF
+#define BM_LEG_MUSCLE _MUSCLES_3E_HILL_
+```
+
+
+## Background
+
+The model is based on published anatomical data produced from a cadaver study in
+the [TLEMsafe EU project](https://tlemsafe.eu/). The first implementation of
+the musculoskeletal model was created by Vincenzo Carbone and René Fluit from
+the University of Twente [^cite_cfpk15].
+
+The key feature of TLEM 2 compared to older TLEM 1 model is a consistent
+dataset, where both muscle attachment and bone surface scans are from the same
+subject. This makes TLEM2 the more anatomically consistent model. Bone contact
+at joints such as the knee thus consists of naturally congruent surfaces, making
+it easier to implement Force Dependent Kinematics on joint movements ({doc}`see
+tutorial <tutorials:ForceDependentKinematics/index>`)
+
+The model was refined during the [Life Long Joints
+project](https://web.archive.org/web/20230108081423/https://lifelongjoints.eu/) where its anatomical fidelity and joint
+force prediction accuracy were improved by De Pieri et al. [^cite_dlgr17], 
+mainly, by implementing better a wrapping surfaces for the muscles ([TLEM
+v2.1](#TLEM2-v2.1)). 
+
+
+::::{figure} _static/Wrapping_TLEM2.png
+:width: 80%
+
+New wrapping surfaces for (clockwise) Gluteus Maximus, Ilio-Psoas, Gluteus
+Medius & Minimus, Hamstrings & Gastrocnemius. All figures are
+from the publication by De Pieri et al. [^cite_dlgr17]
+
+::::
+
+
+Subsequently, the model has been updated again (currently [TLEM
+v2.2](#TLEM2-v2.2)) with muscle wrapping for the Achilles tendon, as well as
+updates to the implementation of the ankle complex in preparation for new multi
+segment foot models. 
+
+
+
+
+
+
+
+## Resources
+
+More details on the TLEM2 model can be found online:
+
+- Webcast: [TLEMsafe: Personalization of musculoskeletal models and prediction of functional outcome](https://www.anybodytech.com/download/tlemsafe-personalization-of-musculoskeletal-models-and-prediction-of-functional-outcome/)
+- Webcast: [TLEMsafe: An integrated system to improve predictability of functional recovery of patients requiring musculoskeletal surgery](https://www.anybodytech.com/download/tlemsafe-an-integrated-system-to-improve-predictability-of-functional-recovery-of-patients-requiring-musculoskeletal-surgery/)
+
+
+
+
+
+## History and changes:
+
+(TLEM2-v2.2)=
+
+TLEM v2.2 (Released in AMMR 3.0.0)
+: Wrapping surfaces have been added to the Achilles tendon around the ankle in
+  the TLEM 2 leg model (now designated TLEM 2.2). This ensures an even ratio of moment arms between
+  the soleus and gastrocnemius muscles. Hence, gastrocnemius is recruited less, 
+  especially during downhill walking and stair descent, solving the tendency of the model 
+  to overpredict the knee contact forces at toe off. 
+  This is the first of a number of improvements to the leg model by Dr. Enrico De Pieri, 
+  who is working on a publication on improvements and validation of the TLEM 2 leg model.
+: The ankle complex has been redefined to compensate for the non-neutral position in which the 
+  cadaver was scanned. The method described in Stolle et al.[^cite_slnbrmv22] was adapted to 
+  identify coordinate systems at the tibia, talus, and calcaneus using their respective 
+  bone surfaces. The coordinate systems were then used to reposition the bone surfaces using 
+  the average values provided in Stolle et al.[^cite_slnbrmv22] for talus-calcaneus and 
+  calcaneus-tibia. These values are based on weight-bearing scans in neutral, bilateral 
+  standing position of 95 healthy adult subjects. This improves the alignment of the tibia, 
+  talus, and calcaneus bones.
+  
+  With the redefined alignment of the ankle complex, the ankle joint axis was updated using 
+  the method described in Montefiori et al.[^cite_mmmmmprhdww19] The joint axis was defined 
+  as the axis of a cylinder fitted to the talar trochlea. The ankle joint centre was defined 
+  at the midpoint of the medial and lateral malleoli projected on the ankle axis.
+
+  The knee joint was also updated to compensate for the non-neutral scan of the cadaver. The
+  updated joint ensures that the patella tendon is straight in the neutral position. 
+  The net effect is rotation of the tibia about its long axis with the feet still pointing in 
+  the same direction in the neutral position. 
+: The foot and talus models have several updates in preparation for the 
+  release of advanced multi-segment foot models in the future:  
+  - The talus coordinate system is updated to be coincident with the foot 
+    coordinate system in the neutral position. This facilitates scaling
+    of subject-specific foot models that would normally include the foot 
+    and talus in the same coordinate system. For backwards compatibility,
+    a new reference node, `TalusCompatibilityFrameAMMR24`, is created in the 
+    talus segment. This reference node has the same position and orientation 
+    as the previous coordinate system of talus.
+  - The update of the talus coordinate system allows reusing some of the 
+    parameters from the foot model and simplifies the code. The talus now uses the
+    subtalar joint parameters from the foot model. The ankle joint parameters 
+    have been updated to be expressed in the new coordinate system. However, 
+    both joints are consistent with the previous implementation. 
+  - The anatomical frames of the foot and the talus are now defined using bony 
+    landmarks on the foot and the lateral and medial malleoli. The vertical axis 
+    is defined as the perpendicular to three coplanar points that can be considered 
+    parallel to the ground. In the new implementation, these are the lowermost points
+    on heel, fifth metatarsal, and medial sesamoid on first metatarsal. This will update 
+    the neutral position of the foot and talus. Moreover, this will also affect the 
+    ankle plantarflexion and subtalar joint angles.
+    :::{warning}
+    Ankle and Subtalar joint angle measures are updated. Please
+    run `MarkerTracking` again for mocap models if using TLEM 2.2.
+    :::
+  - The malleoli coordinates in the foot coordinate system have been fixed to 
+    match the malleoli on the shank in the neutral position.
+  - The model tree has been updated. The talus segment is moved inside the 
+    foot segment. For backwards compatibility, a pointer to the talus segment 
+    still exists outside the foot segment.
+
+The following video compares TLEM v2.2 with TLEM v2.1 (in gray). The knee and
+and ankle joint axes in blue belong to TLEM v2.2 while the ankle joint axes in
+gray belongs to TLEM v2.1
+```{raw} html
+<video width="45%" style="display:block; margin: 0 auto;" controls autoplay loop>
+    <source src="../_static/TLEM22_TLEM21_rotating_model.mp4" type="video/mp4">
+Your browser does not support the video tag.
+</video>
+```
+::::{figure} _static/TLEM22_TLEM21_closeup.jpg
+:width: 80%
+
+Comparison of TLEM v2.2 with TLEM v2.1 (in gray). Please note the patella tendon in
+gray inserts in TLEM v2.1 shank. It depicts the rotational offset of the tibia along
+its axis.
+
+::::
+(TLEM2-v2.1)=
+
+TLEM v2.1 (Released in AMMR 2.0.0)
+: Wrapping surfaces for several muscles were updated. These changes were engineered to
+  result in realistic muscle coordination and hip contact forces as documented
+  in the publication by De Pieri et al. [^cite_dlgr17]
+
+## Citing and references
+
+If you need to cite the model use the following references [^cite_dlgr17], [^cite_cfpk15]. Other useful papers using or related to the TLEM2 model are: [^cite_ca16] and [^cite_ckkv16]. 
+
+
+[^cite_dlgr17]: De Pieri,E., Lund,ME., Gopalakrishnan, A, Rasmussen, KP., Lunn, DE., Ferguson, SJ.
+    “Refining muscle geometry and wrapping in the TLEM 2 model for improved hip contact force prediction”
+    PloS One 13 (2018) ( [link](https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0204109) )
+
+[^cite_cfpk15]: Carbone,V., Fluit,R., Pellikaan,P., van der Krogt,MM., Jansen,D., Damsgaard,M.,
+    Vigneron,L.,Feilkas,T., Koopman,HF., Verdonschot,N.,
+    "Tlem 2.0–A comprehensive musculoskeletal geometry dataset for subject-specific
+    modeling of lower extremity", J. Biomech.,48(5) (2015) 734-741.
+
+
+[^cite_ca16]: Carbone,V., "Subject-specific lower extremity modeling: personalization of
+    musculoskeletal models using medical imaging and functional measurements",
+    PhD thesis, University of Twente, Netherlands (2016).
+
+[^cite_ckkv16]: Carbone,V., van der Krogt,MM., Koopman,HF., Verdonschot,N., "Sensitivity of subject-specific
+    models to Hill muscle-tendon model parameters in simulations of gait",
+    J. Biomech.,49 (2016) 1953-1960.
+
+[^cite_slnbrmv22]: Stolle,J., Lintz,F., de Cesar Netto,C., Bernasconi,A., Rincon,MR., Mathew,R., Vispute,D., Siegler,S. 
+    "Three-dimensional ankle, subtalar, and hindfoot alignment of the normal, weightbearing hindfoot, in bilateral 
+    posture", J. Orthop. Res., 40(10) (2022) 2430-2439 ([link](https://doi.org/10.1002/jor.25267)).
+
+[^cite_mmmmmprhdww19]: Montefiori,E., Modenese,L., Di Marco,R., Magni-Manzoni,S., Malattia,C., Petrarca,M., 
+    Ronchetti,A., de Horatio,LT., van Dijkhuizen,P., Wang,A., Wesarg,S., "An image-based kinematic model of 
+    the tibiotalar and subtalar joints and its application to gait analysis in children with Juvenile 
+    Idiopathic Arthritis", J. Biomech., 85 (2019), 27-36. ([link](https://doi.org/10.1016/j.jbiomech.2018.12.041)).
\ No newline at end of file