How do osteotomies work?

In this third installment of his series on osteotomies, Dr. Grant Garcia details the biomechanics of how changing a bone's alignment physically offloads stress and reduces force on a damaged knee joint.

Here is a summary of the description and key points discussed in the video:

• Normal vs. Abnormal Knee Forces: In a healthy, standard-aligned knee, walking distributes about 60% of the body's force through the inside (medial side) of the joint and roughly 40% through the outside (lateral side). When a patient is bow-legged or knock-kneed, that balance is heavily disrupted. For instance, a bow-legged individual can push 70% to 90% of their body weight entirely through the inner part of the knee, leading to accelerated wear, meniscus damage, and surgical failure if not corrected.
• The Concept of Over-Correction: To successfully offload the damaged, high-pressure zone, surgeons don't just align the leg perfectly straight—they intentionally over-correct it slightly into the opposite direction. If a patient is bow-legged, they are adjusted slightly toward a knock-kneed alignment. This redistributes the daily pressure away from the injured tissue, creating a balanced 50/50 or an inverse 40/60 weight distribution. Over-correction also accounts for the leg naturally settling back over time.
• Offloading the Kneecap: The same logic applies to a tibial tubercle osteotomy. Kneecaps almost always dislocate outward (laterally), causing bone-on-bone friction and arthritis on the outer tracking path. Physically shifting the tubercle bone fragment moves the kneecap away from the localized damage area, easing pressure and keeping it tracking smoothly in its central groove.
• The "Combination Effect": Dr. Garcia emphasizes that if a patient truly needs an osteotomy, it is the single most vital structural procedure they can undergo. While an osteotomy alone reduces joint stress dramatically, combining it with concurrent cartilage or meniscus repairs produces a highly powerful combination effect that yields the best long-term outcomes.