It may help to review how the knee joint works in cycling, which tells us there is a slight rotation between the tibia and femur during the pedal stroke. Link to the full article is included, but I pulled just a couple paragraphs and underlined the pertinent twisting or rotation sentences.
THE PHYSICIAN AND SPORTSMEDICINE – VOL 32 – NO. 4 – APRIL 2004
CPT Chad Asplund, MD; COL Patrick St Pierre, MD
One complete circular movement of the pedals around the bottom bracket is one two-phase pedal cycle. In the power phase, the cyclist pushes down on the pedal and transfers the greatest amount of energy to move the bicycle forward. The power phase begins with the pedal in the 12-o’clock position and ends with the pedal at the 6-o’clock position. The power phase is followed by the recovery phase, which progresses from 6-o’clock back to the 12-o’clock position.
During the pedal cycle, the knee goes through approximately 75° of motion. The knee begins the power phase flexed about 110° and extends to about 35° of flexion. The quadriceps muscle provides most of the force, with input from the hamstring and gluteal muscles. While the knee extends, it also adducts because of the normal valgus angulation of the distal femoral condyles relative to the femoral shaft and foot motion during the power phase. This motion leads to medial translation of the knee during the pedal stroke while the knee extends.
Additionally, the foot pronates during the power phase, causing an internal rotation of the tibia that increases stress on the medial knee. Also, an increased Q angle, seen in females, may further stress the medial joint. During the recovery phase of the pedal stroke, the knee flexes and moves laterally while the tibia externally rotates to ready the leg for the power phase of the next pedal cycle.
Medial Knee Pain
The normal pedaling motion causes the tibia to internally rotate when the knee is extended. Medial knee pain results when increased stress from improper saddle height, saddle fore-and-aft position, or cleat position (toes pointed too far outward) increases internal tibial rotation. Poor leg flexibility and training errors, such as riding in gears that are too high or excessive hill climbing, increase stress and exacerbate medial knee conditions. Anatomic abnormalities,… tibial rotation, and hamstring tightness, may also exacerbate medial knee pain.
Article from LA Times. http://latimes.com
GEAR Getting set for a quicker triathlon BY ROY M. WALLACK
Can techy new gear buy you more speed? I hoped so when I lined up at the start of the recent La Paz Triathlon in Mexico’s Baja California Sur state with some of the most innovative bike and swim gear I’d seen in a while. When the day was done, I was stunned: I’d made a quantum leap. Feeling remarkably fresh, I blew though the finish line 20 minutes faster than ever, breaking three hours for the first time in my life, finishing fourth place in my age group and even coming in before dark at the world’s only afternoon-start “Moonlight Triathlon.” Was it these breakthrough products that transformed me from laggard to stud? As it turns out, probably not as much as I initially thought. An hour later, a friend informed me that I’d missed a turn and unintentionally cut three miles off of the run course. Most likely, I’d have finished seventh at best in my category. Bottom line: The novel inventions here offer real benefits to triathletes. Who knows? If you train right and pay attention to the route, you might even shave a minute or two off your personal record.
The skate pedal
Nikola Innovations lateral motion pedals: These pedals slide an inch (25 millimeters) sideways through the pedal stroke. The motion reflects Ohio inventor Nick Stevovich’s attempt to create a more powerful and safer, biomechanically efficient movement pattern that combines cycling with the lateral propulsion and joint ease of skating.
Likes: The motion is smooth, enjoyable and efficient, and it feels similar to normal cycling. Nikola claims studies show that lateral motion pedals deliver an average savings of more than two minutes in a 40K time trial and a 7% increase in peak wattage; 70% of users report increased power. Stevovich says that while everyone may not get faster, most will experience easier hill climbing and fewer knee and hip irritations and injuries. I would agree on the hill climbing. An athletic-injury specialist I spoke with, Dr. Eric Tortosa, speculated that the design would increase power due to fuller leg extension while subjecting the medial compartment of the knee to less load and injury risk than regular pedaling. The pedal comes with standard three-hole Look-style cletes.
Dislikes: It’s expensive and heavy. It requires extra care during setup and an oversized 8 mm wrench to install and remove.
Price: $339 for the 502-gram stainless steel model; $549 for the 370 g pair of titanium; http://nikolainnovation.com