For many, running is seen as a timeline and not a skill that needs to be sharpened following surgery. One of the first questions most patients ask after knee surgery is when can I run? They want a date. A specific time. While it is important to educate our patient's on general time frames for recovery and how long it takes a specific tissue to heal, giving a specific date for return to activity can be challenging.There are many things they need to achieve before returning to the track, roads, or trails.
While slight variations exist in timelines for recovery from knee surgery, the overall progress through physical therapy is very similar. Manage pain and swelling, restore knee ROM, improve strength, and return to functional and sport activities. Many steps exist within each of these goals, but the overall process is somewhat similar whether a patient has undergone an ACL repair, microfracture, or other operative procedure. Unfortunately, a lot of runners return to running too quick.
1. Restoring full ACTIVE knee flexion in prone and standing
We can break the running gait cycle down into two phases: stance phase and swing phase. A majority of our time post operatively is focused on restoring the stance phase portion. Being able to perform single leg, closed-chain exercises is a vital part of a successful rehabilitation. An often overlooked part of returning to running is restoring a runner's swing phase.
Healthy and injured runners exhibit large differences in their swing phase mechanics. Some exhibit more knee flexion, some less, etc. Look at the large difference in swing mechanics between two of my high school clients. Both are NCAA level runners who have been injury free for the past two seasons. Yet, they exhibit very different swing phase mechanics.
Here is one of my favorite drills for restoring a runner's swing phase.
2. Improving rate of force development
Running is a demanding sport. The body has to deal with a lot of force and it happens quick. With every foot contact, we are asking our body to support two to three times our body weight. If a runner runs at a cadence of 180 steps per minute, for a 30 minute run, that's 5400 foot contacts. Your body better be ready for it.
Make them produce force QUICKLY. Simply mastering your bodyweight with single leg challenges is a great place for runners to start when they are returning to training, but it CAN'T be the end. Getting strong and powerful has advantages not only for overall health and injury reduction, but also performance. Below are two hopping variations I use with both healthy and injured runners to improve their "springiness".
3. Optimizing running mechanics based on pathology
Different running styles load our body differently. While there is not an ideal way to run for everyone, there are some things we might want to avoid when dealing with a post-surgical patient. In order to allow our patients to be in the best position to succeed we need to both understand the biomechanics of running gait as well as take a broad look at how we can help them make a change in how they are moving if needed.
One of the most challenging aspects of progressing a post-operative patient back to running is the management of "joint issues". Damage to the joint surfaces, either through the surgical process (ex. menisectomy, microfracture, etc.) changes the passive stability of the knee joint. Even if someone has an isolated ACL repair, the majority of those injuries also have some amount of bone bruising that happens between the joint surfaces of the tibia and femur. These deficits in joint structure can lead to changes in the joints passive stability and can affect the recovery process. We need to make sure we are avoiding any excess stress that might be placed on the knee both due to lack of strength and power and well as mechanics that put more stress around the knee.
Running at a lower cadence puts more of a demand on the knee then running at a quicker pace. In general, having our foot on the ground for a longer amount of time is probably not the best idea for a runner following knee surgery. Cadence manipulation can be extremely beneficial at reducing loads throughout the knee and is something that should be assessed when a patient is getting back to running. If you've got a runner hovering around 150 steps per minute, it's probably in their best interest to get their cadence up a little higher. Chris Johnson has a great summary of relevant research related to cadence and the knee at http://runcadence.net/science-2/.
4. Speed and variability with returning to run
For many people, running is seen as a single, basic activity. In reality, running is a series of complex skills that are important to master. Variations in a runner's speed and environment will change the demand on different structures of the body. Running a 50k trail race is very different then a 5k road race. With many return to run progressions, a runner will simply go out and run a set amount of time and pay little attention to the speed they are running.
It makes sense to ease runners back into running slowly, but we have research that now says running at slower speeds puts an increase amount of load at the knee. Slogging out a bunch of slow miles at a low cadence probably isn't the best bet for a runner following knee surgery. Having small amounts of variability in speed, surface type, and overall training environment allows the body to adapt to many different types of stressors.
Returning to running after surgery can be tough. More then anything, runners need to PAY ATTENTION and remain patient so they can get back to doing the things they enjoy!
Noll S, Garrison J, Bothwell J et al. Knee Extension Range of Motion at 4 weeks is Related to Knee Extension Loss at 12 weeks After Anterior Cruciate Ligament Reconstruction.
Shelbourne KD1, Urch SE, Gray T, Freeman H. Loss of normal knee motion after anterior cruciate ligament reconstruction is associated with radiographic arthritic changes after surgery. Am J Sports Med. 2012 Jan; 40 (1):108-113
Petersen J, et al. Cumulative loads increase at the knee joint with slow-speed running compared to faster running: a biomechanical study. J Orthop Sports Phys There. 2015
Willy RW, et al. Changes in tibiofemoral contact forces during running in response to in-field gait retraining. J Sports Sci. 2016.