Ankle Sprain Knee Pain? The Ankle Bone’s Connected to the Knee Bone…
What if you have ankle sprain knee pain? More precisely, what if you have an ankle injury and later develop knee pain; are they connected? Will your doctor connect the dots? Regrettably, my medical doctor brethren are generally horrible at thinking bio mechanically. A 37 year old personal trainer I just saw in clinic is a great example of why I think that and why it’s so important that we change. Since her knee hurt, the focus was on her knee, but what was forgotten was that the ankle bone is connected to the knee bone.
How did we doctors get so clueless about how the body’s musculoskeletal system works? First, we get no training in this area in medical school. Second, specialties that should know about these things, like orthopedic surgery and pain management, instead often focus on a “pain generator” approach to patients. For orthopedic surgeons, that focus is to take a complaint like knee pain and then look for something structurally wrong in the knee. The issue with that method is that just about everyone over 40 with or without knee pain has issues that can be detected on our latest sensitive MRI equipment.
The 37 year old I saw in clinic will illustrate these problems in approach to a patient very nicely. This woman had outside knee pain that developed after returning back to running and training for a triathlon (the big Boulder Iron-man in August). She was most tender at the head of the fibula (the outside small bone of the knee) and her ultrasound showed some early small cysts in that outside meniscus, but everything else was unimpressive. She went back to see her orthopedic surgeon who told her that if PT didn’t help, they could perform a diagnostic arthroscopy for a meniscus tear. In getting the history and before examining her knee, I found out that last year she had rolled that ankle and pulled off a piece of bone. This was treated by immobilization in a boot for 6 weeks. This seemed to heal and her surgeon cleared the ankle as not needing surgery, so she began the long rehab back to competition. It was in that recovery that she noticed ankle soreness after her runs (which she ignored because she felt it would go away). Eventually once she increased her mileage enough, the knee began to hurt.
Hearing all of this, my first exam wasn’t her knee. After more than two and a half decades of doing this work I realized that anybody with enough force on the outside ankle ligament so that the ligament yanks off the piece of bone it’s attached to, could have also trashed that ligament. Sure enough, the main ankle ligament (CF or calcaneofibular) was very unstable on ultrasound stress testing. I then examined her knee and found that her LCL ligament that attaches to the top of the same fibula bone was also unstable. The picture above shows why this outside knee ligament got stretched. When she rolled her ankle, her outside ankle ligaments were stretched hard, but her knee also translated outward in response, also injuring her outside knee ligament. She then went into a walking boot, which had the effect of protecting the knee, so her knee didn’t hurt much. When she began upping her miles, the unstable outside ankle ligament allowed too much ankle motion (thus the pain and swelling after runs) and her outside knee ligament allowed too much motion there (which was also aided by the extra forces now coming from a loose fibula bone that was not well anchored by strong ligaments at the bottom or the top). This led to her knee pain. As a result, this personal trainer needed as much attention paid to her ankle as her knee. She’s now undergoing regenerative ligament injections at both sites.
The upshot? We doctors are horrible at bio mechanics and as a result, diagnoses and causes of problems are often missed. Take a minute to read our e-book Orthopedics 2.0 if you want to learn about how your body works and become your own advocate for high quality musculoskeletal care that looks at causes and not symptoms. In the meantime, if you’ve sprained or injured your ankle and your knee later suddenly starts hurting, at least now you know one reason why!