Knee replacements are individualised for each patient
Knee replacements are a common solution for severe knee pain and mobility issues, often caused by arthritis. In this article, I discuss different alignment approaches used by orthopaedic surgeons in knee replacements, as well as my preferred methods.
Alignment in knee replacements refers to the positioning of the new knee joint and how this affects the angle and movement of your leg. The way that the knee is aligned plays an important role in long-term outcomes and patient satisfaction.
Alignment philosophies and what they mean
There are different alignment philosophies, and each surgeon may favour a different approach. In simple terms, the alignment approaches are:
- Mechanical alignment: With mechanical alignment, if your leg is skew before the surgery (for example, bow-legged), it will be straight after the operation. The goal is to ensure a straight line from the middle of the hip to the middle of the knee, to the middle of the ankle. This technique has been used for many years and generally yields good outcomes.
- Kinematic alignment: In this approach, the alignment of the person’s leg stays the same as it was before the surgery. For example, if you were bow-legged before the surgery, your leg will still be bow-legged after the operation. This approach is newer than mechanical alignment but has also been used for many years. Not every patient will be a candidate for this approach, as their ligaments may be damaged when trying to achieve kinematic alignment.
Personalised and functional alignment
The alignment approach which I prefer is personalised alignment, which takes a patient’s unique anatomy and movement patterns into account. This means that at the end of the knee replacement surgery, the patient’s alignment might fall somewhere between mechanical and kinematic alignments. For example, if you were bow-legged before the surgery, you might still be slightly bow-legged afterwards, but not as bow-legged as you were before.
I use a robot to assist with knee replacement surgery in certain patients. When we use a robot to achieve a personalised alignment, it is called functional alignment.
- For a more in-depth and technical understanding of these alignment philosophies, read my previous article:
One of the main reasons I favour personalised and functional alignment is because I try to avoid releasing (cutting) a patient’s ligaments. This is because it is challenging to know exactly how much ligament to cut to balance the knee. Due to the soft and stretchy nature of these tissues, it is easy to cut away too much ligament. With bone, on the other hand, it is easy to measure and cut precise amounts because bone is hard.
Choosing an alignment approach for the best patient outcomes
The above is a simplified overview of how we approach alignment in knee replacements. In reality, we take much more into account. The knee is a three-dimensional joint, so we look at it on all planes when deciding on alignment. We also consider a patient’s soft tissue (ligaments), their alignment before surgery, the condition of the other leg, and the condition of their hip and spine.
Your surgeon will take all these factors into account to decide on the best approach and alignment for your unique anatomy. Using the personalised and functional alignment approaches, I aim to achieve stability, balance and reduce pain for my patients.