Dnsys Z1 SingleJoint Left Leg + X1 Carbon

A left anterior cruciate ligament (ACL) tear is one of the most frequent ligament injuries in sport, particularly affecting pivoting sports (skiing, soccer, handball, basketball) and trail runners on technical terrain. The Dnsys Z1 SingleJoint Left + X1 Carbon bundle can play a significant role at different stages of managing this injury — with important distinctions depending on whether the tear is treated surgically or conservatively.

For a surgically treated tear (ligament reconstruction, typically with a patellar tendon or hamstring graft), the bundle is indicated in the advanced recovery phase, generally from the 4th to 6th month after surgery depending on the surgeon's and physiotherapist's protocols. In this phase, the knee's stabilizing muscles (quadriceps, hamstrings) have been sufficiently reconditioned but confidence in the operated knee is not yet fully restored — this is the period of “kinesiophobia” (fear of re-injuring the knee) that often holds back the return to outdoor activities.

In this phase the left Z1 SingleJoint provides external mechanical support that compensates for the proprioception deficit (the perception of the knee's position in space) that persists for several months after ligament reconstruction. This support lets the patient venture onto varied terrain with a reduced risk of a “false move” on the operated knee, speeding functional recovery and the return of confidence. The X1 Carbon, by assisting the left hip, simultaneously reduces fatigue in the operated leg on climbs — allowing longer outings without over-stressing the limb in recovery.

For a conservatively treated tear (no surgery, with muscle strengthening only), the bundle can be used from the end of the initial ligament consolidation phase (about 6 weeks after the tear), on medical advice. The Z1's left unilateral assistance allows a return to moderate outdoor activities while protecting the ACL from excessive valgus and internal-rotation stress.

An important clarification: the left Z1 SingleJoint does not mechanically prevent rotation of the knee (anterior tibial drawer or forced internal rotation, which cause ACL tears). It reduces compressive loads and provides a proprioceptive reminder, but it is not a ligament-reconstruction orthosis with rigid mechanical restraint. For high-intensity pivoting sports (skiing, competitive soccer), a custom rigid post-ACL brace remains the most appropriate protective device. The Dnsys bundle is ideal for the gradual return to hiking, light trail running and mountain walking.

The question of the modularity of the Dnsys system — and in particular of using the Z1 SingleJoint Left alone without the X1 Carbon — is very relevant for users whose needs vary by situation. The answer is yes, with a few important nuances.

The Z1 SingleJoint Left is a standalone device that can work independently of the X1 Carbon. It has its own battery (14 to 16 km of range), its own AI processor and its own Bluetooth pairing with the Dnsys app. In solo mode (with no X1 Carbon connected), the algorithm switches to “knee-only mode” — it optimizes left-knee assistance without receiving the complementary hip data the X1 Carbon would normally provide. The Z1's solo performance is very good for urban uses and moderate activities; it is on hilly terrain and significant elevation gain that the X1 Carbon's extra contribution is felt most.

The situations where using the Z1 alone is natural and relevant. City walking and daily travel: on flat, paved ground, hip assistance is not essential — the Z1 alone is enough to relieve the left knee over a long day of urban walking. Indoor activities (museums, shopping, work trips): putting on the full X1 Carbon for a museum visit can be excessive — the Z1 alone, more discreet, assists the knee without the full equipment. Guided rehabilitation: during physiotherapy sessions, the therapist may prefer to observe and work on the knee alone, without the hip exoskeleton that changes the overall gait pattern.

The situations where adding the X1 Carbon is recommended. As soon as the hike includes elevation gain (from 100-150 m), hip fatigue interacts significantly with knee fatigue. For outings of more than 8 km. For uneven, technical terrain where hip-knee coordination is called on. For users with a hip condition associated with the knee condition.

Switching between “Z1 alone” mode and “Z1+X1 bundle” mode is automatic — the Dnsys app detects which modules are switched on and connected, and adapts the algorithm accordingly. You do not have to reconfigure anything when you go out with either configuration.

Managing asymmetry is one of the most interesting technical challenges the AI algorithm of the Dnsys Z1 SingleJoint Left + X1 Carbon bundle has to solve. Assisting a single leg in a fundamentally bilateral locomotor system without creating postural dysfunction or harmful compensation is a complex problem that Dnsys engineers have approached in an original way.

The basic problem is this: if the left knee receives motor assistance and the right one does not, the two legs no longer provide the same amount of effort in each walking cycle. Without correction, this would create an asymmetry of force and timing between the two limbs, resulting in a limping gait or a pelvic tilt toward the unassisted side.

The algorithm solves this problem by adopting an asymmetric adaptive assistance strategy. The AI continuously analyzes the metrics of both legs (even if the right is not assisted, the X1 Carbon's inertial sensors measure the movement of the WHOLE pelvis, making it possible to infer the behavior of both legs). It compares the perceived effort level of the left (assisted) and right (unassisted) leg in each cycle. If the metrics indicate satisfactory symmetry (both legs contribute equally to propulsion), assistance stays at its nominal level. If an asymmetry develops (the assisted leg “takes more” than the right), left-knee assistance is slightly reduced to keep the balance.

This approach is fundamentally different from fixed assistance on the right and none on the left — it is a continuous real-time modulation that aims to maintain a natural symmetrical gait. The aim is not to make the left leg perform better than the right, but to make it perform as well as the right throughout the outing, despite its condition.

In practice, users of the left unilateral bundle report that their gait is significantly more symmetrical than with a passive orthosis, and that end-of-outing fatigue is spread more evenly between the two legs than when walking without assistance. RNM mode (available if the configuration includes an X1 Carbon Pro) amplifies this effect by detecting fatigue-related stride asymmetries and adjusting assistance to compensate for them.

Integrating the Dnsys Z1 SingleJoint Left + X1 Carbon bundle into a physiotherapy protocol is a growing application, driven by innovative physiotherapists who see personal exoskeletons as a complementary tool for functional rehabilitation outside the clinic. Here is how this integration works in practice and what healthcare professionals need to know.

The fundamental distinction between use in rehabilitation and sporting use is the assistance philosophy. In a sporting context, you maximize assistance so the user can go further or higher than they could alone. In rehabilitation, the goal is often the opposite: use the minimum assistance needed to allow correct movement, while maintaining maximum active muscle engagement. The Dnsys app has a Rehabilitation mode (accessible only from the healthcare-professional account) that lets you precisely set the assistance percentage and change it gradually week by week according to the patient's progress.

The typical protocol recommended for integrating the bundle into left post-ACL rehabilitation (as an example) runs as follows. Phase 1 (weeks 1-2 of using the bundle): Z1 assistance at 70%, X1 assistance at 50% — the patient regains confidence walking on varied terrain with a high level of protection. Phase 2 (weeks 3-4): Z1 assistance reduced to 50%, X1 assistance at 40% — the muscles are more engaged, proprioception is rebuilt. Phase 3 (weeks 5-8): Z1 assistance at 30%, X1 assistance at 20% — the patient is approaching weaning off the exoskeleton, muscle engagement is close to normal. Phase 4 (beyond): minimal assistance (10-15%) or stopping the bundle, with occasional use for particularly demanding terrain.

For physiotherapists who want to bring the bundle into their practice, Dnsys offers a 3-hour online training (Dnsys Rehabilitation certification) covering how the device works, use of Rehabilitation mode, indications and contraindications, and recommended progression protocols. Certified professionals have access to a patient-monitoring console that lets them remotely follow their patients' walking data between sessions — symmetry, assistance level used, mileage, changes in stride metrics. This functional remote monitoring is a valuable tool for adjusting protocols remotely and encouraging regular practice between sessions.

The unilateral configuration of the Dnsys Z1 SingleJoint Left Leg + X1 Carbon bundle answers specific situations where assistance is only needed on one leg — the left, in this case. Choosing a unilateral system over a bilateral one is not a budget compromise; it is often the most appropriate biomechanical choice depending on the nature of the condition or limitation.

The main indications for a left unilateral configuration are as follows. Strictly unilateral conditions: osteoarthritis of the left knee only, a ligament or meniscal injury on the left side, after-effects of a fracture or surgery on the left leg, unilateral muscle weakness (after-effects of peripheral nerve injury, post-immobilization weakness). Correcting a functional asymmetry: some people have a “dominant” right leg and a structurally or functionally weaker left leg — the left unilateral configuration compensates for this asymmetry without disturbing the healthy right leg. A progressive trial before investing in a bilateral bundle: starting with the unilateral configuration on the weaker leg lets you assess the exoskeleton's benefits before extending the investment.

The advantage of the unilateral configuration over the bilateral one is not only economic. Biomechanically, providing assistance only to the leg that needs it respects natural neuromotor plasticity. If the right leg is healthy and capable, letting it work freely maintains its level of muscle engagement and preserves its strength. Assisting both legs symmetrically when only one needs it could reduce the engagement of the healthy leg and eventually create unnecessary dependence.

The AI algorithm of the Z1 Left + X1 Carbon bundle handles left hip-knee coordination with the same sophistication as in the bilateral bundle. It also takes into account the asymmetry introduced by the right knee not being assisted — it adapts hip assistance (X1 Carbon) to compensate for load differences between the two sides, maintaining a balanced overall posture despite unilateral assistance.

If your condition is resolved in time (for example, rehabilitation after left knee surgery), the left unilateral configuration can be upgraded to a bilateral one by simply adding a right Z1 module, or dropped once recovery is complete. This modularity is one of the Dnsys system's fundamental strengths.