Kinesio Tape debunked with simple physics
Simple physics will explain why the popular Kinesio Tape cannot mechanically support the joints as claimed.
If I hold a dumbbell and move into 90° of elbow flexion, if the dumbbell is 10lbs and my distance from the axis (radial ulnar joint) is 12" my elbow flexors have to recruit "approximately" 120 inch/lbs or torque in the opposite direction at the axis to maintain a static position. That is using a joint which only allows for one degree of freedom and moves in only one plane. Forget multi-planar joints...
A 10lb dumbbell is proprioceptively a relatively low amount of resistance in the average persons hand at 90°. Even though the "steel cables" known as muscles have to generate tremendous amounts of force for simple low resistance motions and/or positions.
Even if kinesio tape had the tensile strength to prevent a change in length with more than a few ounces of force, it still is impossible for it to directly, mechanically support any joint. The reality is that kinesio tape is unable to attach directly to the muscles, the body has a barrier layer of skin, epidermis, dermis and subcutaneous fat which stretch tremendously. Anyone who has cut through a cadaver would concur. The next layer down is the connective tissue which on a microscopic scale stretches like flexible scaffolding and returns to its shape after the stretch, we relate this to the "theory of tensegrity" in physics.
Take that all into consideration, now lets hypothetically take a therapist who would tape up a patients knee who is experiencing patellar tendonitis. The amount of force generated through the muscles, into or around the knee, when an athlete is performing a sport or a high intensity activity, is incredibly great.
This magnitude of force can reach into the hundreds or even thousands of pounds at the axis of the knee. Kinesio tape doesn't even come close to aiding in direct mechanical support for these intrinsic forces, if KT stretches lengthwise and returns to neutral with only an ounce or two of elastic force in the opposite direction, it would be reasonable to conclude that it cannot provide enough mechanical support to directly influence joint function.
All that being said. I can see where KT can potentially have an indirect "non mechanical" influence on joint function. It obviously provides sensory input to the afferrent nocioceptors in the skin. This sensory input can create a reminder to the athlete to not go into a vulnerable range of motion.
For example, if a client/patient had a hip extensor strain, one could use the tape to create a "stretching sensation" on the skin as the hip moves further into flexion, this could be theoretically used as nocioceptive reminder to the client/patient to not go further into that range, any further degrees of motion into flexion would potentially put too much tension on the hip extensors which are moving into a lengthened position. This "reminder" used in this manner could allow the tissues to heal by keeping them temporarily in a safe range of motion. This is all theoretical and cannot be substantiated. Nor does this therapy address root causes of joint or tissue dysfunction. As we know, ligaments and muscles provide stability for all the joints in the body. They are incredibly complex, there is no man made material which can appropriately replicate their characteristics.
The final nail in the coffin for KT is that the practitioners by majority cannot fathom or calculate the forces which move through the joints during motions which athletes go through in a day. Bio-mechanists would have a hard time with that calculation...and that's what they are trained to do.
If the practitioner can't easily predict the vectors and magnitudes of force needed to dynamically control multi-planar and multi-axial motions. How in the hell can we use a stretchy tape to address a joint calculus equation we cannot even calculate, by laying spiral lines of stretchy tape on stretchy skin??