Gait deviations before and after knee surgery are common. Pain at the knee can affect weight bearing tolerance and weight acceptance, knee range of motion, and quadriceps function.
One of the more common gait deviations surrounding knee pain and surgery is termed "quadriceps avoidance". This has been defined in various ways and can be safely defined as any gait pattern which avoids the activation and work of the quadriceps.
The reasons someone might avoid quadriceps function include pain, limited range of motion, swelling, quadriceps weakness, and unwanted joint sounds (crepitus).
Although quadriceps avoidance is common initially after surgery due to the above mentioned causes, as time after surgery progresses, this gait deviation limits functional progress.
Multiple studies have shown gait deviations up to 8-12 months after knee surgeries such as ACL reconstruction, meniscectomy, and total knee replacement.
So, let's take a closer look at what quadriceps avoidance looks like and we will dive deeper into the causes of this gait deviation.
Role Of The Quadriceps In Gait
The primary role of the quadriceps during gait is to support body weight during moments when the knee is in a flexed position. This occurs during a phase of gait termed "loading response".
The 8 phases of gait in order are: Initial contact, loading response, mid stance, terminal stance, pre-swing, initial swing, mid swing, and terminal swing.
Before your quadriceps help support body weight in loading response, they assist with knee extension during terminal swing. This action works to extend the knee to prepare for initial contact and the heel rocker. The quadriceps will stay active from terminal swing until the beginning of mid-stance at which point the muscle activity greatly diminishes.
EMG Graph of Rectus Femoris With Pressure Graph From Walking Gait Analysis With the quadriceps playing a key role in assisting knee extension and controlling rapid knee flexion, it is important therefore to assess knee range of motion during gait analysis. Combining EMG muscle activation data and knee range of motion data is the best way to recognize quadriceps avoidance in gait analysis.
Comparison: Knee Range Of Motion With And Without Quadriceps Avoidance
For the lower extremity to adequately absorb shock and progress the body forward the knee must move through a functional range of knee extension and flexion.
At initial contact, the knee is at or near full extension (0-5 degrees). This helps to create a rigid hinge at the knee while the your body weight progresses over the heel - this is known as a "heel rocker".
Following initial contact, the knee must bend during loading response in order to absorb the weight of the body falling towards the ground due to gravity. Typically, the knee will bend to approximately 20 degrees during this phase of gait.
Right after loading response, the knee will return back to full extension to assist with propulsion.
So, in typical unimpaired gait, knee range of motion will progress from 0 degrees at initial contact, to 20 degrees during loading response, and return to 0 degrees during mid-stance.
What does knee range of motion look like when atrophy and weakness impairs quadriceps function as in the case of quadriceps avoidance?
Knee Flexion Angle During Loading Response In Uninjured Gait
Knee Flexion Angle During Loading Response With Quadriceps Avoidance
In the second graph example above you notice a relatively straight line between each peak. This represents a lack of knee flexion from loading response to mid-stance. From an observation or video standpoint, the knee would look fully straight for the duration of the gait cycle as in this video example below.
In situations where sufficient knee range of motion is present, a locked or extended knee during the gait cycle would indicate a hesitancy or avoidance of quadriceps activity. Quadriceps avoidance is usually a subconscious event mediated by neuromuscular pathways in the presence of quadriceps atrophy, weakness, and pain.
In a straight knee position, the congruency and contact surfaces of the femur and tibia allow for "bony" stability when "muscular" stability is lacking. To normalize level walking gait, specific biofeedback training with video, angle measurement, and tactile cues is necessary.
Early Independent Walking Gait Vs. Normalized Walking Gait
Right after knee surgery every client asks, "When can I walk again."
Often times, patients will begin independent ambulation early in their recovery. Eager to return to normal function, they ditch the crutches or cane and hobble around with subtle to obvious gait limitations.
From a rehabilitation perspective, early gait is encouraged when the proper muscular, range of motion, and balance foundation is in place.
Sufficient quadriceps muscle activation and strength is necessary to absorb shock in the loading response phase of gait and assist with knee extension prior to initial contact.
Walking early in rehabilitation can be detrimental to proper gait if quadriceps avoidance is demonstrated.
Walking with either a bent knee or full extended knee for the duration of the gait cycle represents a limitation at the quadriceps and a need to address quadriceps muscle function before continued walking.
As with other activities, quality of movement is paramount over quantity of movement. Avoid band habits with walking early on and your return to a normalized gait will be much easier.
Treating Quadriceps Avoidance
At the start of rehabilitation following surgery, immediately address any limitations in quadriceps activation and strength. This can be monitored with EMG muscle analysis or visual/tactile assessment during a quad set or straight leg raise. Too often, other lower extremity muscles such as the gluteus maximus take over during quadriceps training.
Once weight bearing is allowed by your MD, you can start closed-chain lower extremity strengthening exercises such as squats and step ups. To specifically challenge the quadriceps to improve gait, perform eccentric strengthening drills. This can be done using a band around the knee with terminal knee extensions, step downs, or lunges.
It is common to be hesitant and nervous about these exercises and your physical therapist will lead you through the proper form.
Quadriceps avoidance is a common gait deviation following knee injury or surgery and using this guide will help you pinpoint specific cases and begin the training back to efficient walking.
Kevin Vandi, DPT, OCS, CSCS
Dr. Vandi is the founder of Competitive EDGE Physical Therapy — with his background in physical therapy, orthopedics, and biomechanics, he is a highly educated, compassionate specialist. Using state-of-the-art motion analysis technology and data-driven methodologies, Kevin has assisted a wide range of clients, from post-surgery patients to youth and professional athletes. When he isn’t busy working or reading research, he spends his time with his wife Chrissy and their five wonderful children, often enjoying the outdoors and staying committed to an active lifestyle.