Simulated knee flexion contracture to elucidate knee-spine syndrome

When we have on one side either a:
- fixed knee flexion deficit
- weak quadriceps mechanism
- short quadriceps-hip flexor complex with anterior pelvis predominance

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. . . these often present functionally as a short leg on that side. Perhaps better put, these will cause a premature forefoot loading response. This loading response will expedite ankle rocker during the stance phase of gait. This will often result in an overactive calf muscle complex and thus shortness over time, further blunting the ankle rocker during tibial progression over the ankle.
Furthermore, there will be a heavy lurching loading response on that same leg, it will surely look like a short leg, functionally. This is why it is imperative to check for full knee extension, ability to engage the quads with endurance and strength in full extension, and be able to connect that anterior chain with the lower abdominals and hip flexors without dumping into an anterior pelvis posture.
The loads move. They move up and down. There are many other causes of this descriptive mechanical chain problem above. Even a weak anterior shin compartment will cause many of these abrupt forefoot loading responses (that can also functionally resemble a knee flexion contracture) and promote early and excessive knee flexion during early limb loading response, when we rather should be posturing over a more stable and extended knee. They feed off of each other. It is why these syndromes of problems get intermixed and complicated to both diagnose and remedy.

PS: we chose this photo for a reason today, because high heels make us load the forefoot prematurely during the gait cycle, and we have to dampen the loads with the quadriceps.

Take what you will from this study, but it is really the global picture it suggests. That being, everything can affect everything.
PS: we hate the name they put on this study at the end. . . . "Knee-spine syndrome". For what its worth.

"However, the 30 degrees (simulated knee) contracture significantly changed the kinematics in each of the following planes. In the coronal plane, the trunk tilted to the contracture side in standing and walking. In the sagittal plane, posterior inclination of the pelvis in standing significantly increased. In addition, anterior inclination of the trunk and pelvis during walking significantly increased. In the axial plane, trunk rotation to the unaffected side significantly decreased during walking. The vertical knee force in the contracture limb decreased, being accompanied by the increase of the force in the unaffected limb during standing and walking. Results of our study suggest that knee flexion contracture significantly influences three-dimensional trunk kinematics during relaxed standing and level walking, and will lead to spinal imbalance. These facts may explain the onset of the "Knee-Spine Syndrome".

Gait Posture. 2008 Nov;28(4):687-92. doi: 10.1016/j.gaitpost.2008.05.008. Epub 2008 Jun 26.

A gait analysis of simulated knee flexion contracture to elucidate knee-spine syndrome.

Harato K1, Nagura T, Matsumoto H, Otani T, Toyama Y, Suda Y.