Two Key Concepts: Muscle Inhibition and Recruitment

Muscle Inhibition

Inhibition is marked weakness of the quadriceps muscles, and that is typically observed following an injury, surgery or pathology effecting the knee joint. This is partly due to ongoing neural inhibition that prevents the central nervous system from fully activating the quadriceps muscle, a process known as arthrogenic muscle inhibition, or AMI. Essentially this is the inability of the nervous system to activate the muscles.

Muscle Recruitment

Motor unit recruitment refers to the activation of additional motor units to accomplish an increase in contractile strength in a muscle. Contractile meaning contraction, the ability for the muscle to contract. A single motor unit consists of one motor neuron and all the muscle fibers it stimulates, so we’re really getting into the muscle to recruit one motor neuron to activate that portion of the muscle that that controls.

Expectations After Knee Surgery

The general expectations are that your knee is going to swell up. You will have tightness in your knee. Pain is going to be part of the surgery and recovery. Physical therapy and mobility are the key important things that you will want to address following any knee surgeries.

During the initial few days after knee surgery you are going to work more on range of motion, decreasing the amount of swelling in the knee, and keeping your legs iced and elevated. That decreases the amount of inflammation following the surgery and thereby, having very little chance for developing a scar tissue in your knee joint.

Generally after a knee surgery when your knee joint has swollen up, there is a lot of exudation and fluid build up. These fluids can ultimately result to a scar tissue formation wherein your range of motion can be restricted. Or, maybe, making it hard for you to regain your range of motion. Exercising and moving, mobilizing your joint, helps prevent and decrease the exudation, thereby helping you to prevent the development of scar tissue.

Recovery following a total knee replacement involves not only range of motion but also control. The quadriceps muscle group goes into a stage called muscle inhibition. And wherein these fibers do not act, and do not get recruited, they need facilitation (movement) just to let the body know, and especially the muscle know, that it is okay to move. It’s needed, so this facilitation helps in breaking up this quadriceps inhibition and thereby, the control of the joint does return.

What happens with most patients is that when they don’t have this control there is a good chance of them buckling and having a fall. Muscle recruitment and breaking the cycle of early inhibition is more important in the recovery process during the initial few weeks following your surgery.

Key Concept: Proprioception

Proprioception is the medical term that describes the ability to sense the orientation of your body in your environment. It allows you to move quickly and freely without having to consciously think about where you are in space or in your environment. Proprioception is a constant feedback loop within your nervous system, telling your brain what position you are in and what forces are acting upon your body at any given point in time.

Strength and the Risk of Falling

I’ve worked with some patients who have had a fall. Your knee joint has certain specialized receptors. Proprioception, which tells you where your joint is, is one of them. And following surgery with the amount of swelling and the stiffness, some of these receptors do not communicate well. As a patient, you might not be in a position to tell whether you knee is bent, or is it straight, or whether it can bear weight. And that is one of the reasons you can have more falls earlier in the recovery process. Pre-training (Pre-Hab) and regular exercises and use of mobilizations should help you decrease those fluids, and thereby help you recover your knee joint range of motion.

Your quadriceps is a muscle that is in the front of your thigh. It is the muscle that is responsible primarily for straightening your knee, which we call extension.

Your hamstring muscle, which is on the back of your thigh, are the flexors and they help in bending your knee, also called flexion.

The calf muscles, also known as soleus, and gasctrocnemius muscles, are responsible both for straightening your knee as well as to control and propel yourself forward by doing your plantar flexion, your foot movements.

Basically for strengthening, you want it to strengthen all the three groups of your muscles to get the maximum results and benefits.

A Stiff Knee and Your Walking Pattern

In general what we notice postoperatively is that knee patients tend to maintain a stiff knee, and they try to use more of their hip and bring their legs forward to walk. But we want you to retrain and walk with a heel-toe gait, which involves your hip to bend, your knee to bend and your ankle to move up, and your foot to move up, so your heel can touch the floor.

For this synchronization to happen we need absolute control over your knee joint and also range of motion in your knee joint and strength to withstand your body weight. This is where we use assisted devices like canes and walkers to help you support your body weight while retraining how to walk.

Strengthening is a key component of any rehab program following knee surgery. For you to get back to your daily activities and functional activities and things that you want to do like walk outside, you need absolute control. Control is starts with strengthening. You need to start strengthening your muscles on a continual basis to be able to walk and get to the activities, and functional activities that you want to do.

Key Concept: Muscle Strength Scale

The severity of muscle weakness can be classified into different strength grades based upon the following criteria:

• Grade Zero, no contraction or muscle movement. That’s the worst.
• Grade One, a trace of contraction, but no movement at the joint.
• Grade Two, movement of the joint with gravity eliminated.
• Grade Three, movement against gravity but not against added resistance.
• Grade Four, movement against external resistance with less strength than usual.
• Grade Five, which is normal strength.

Pre-habilition Before Knee Surgery

Prior to surgery patients generally tend to lose muscle strength, at least by a grade. This is so true for the quadriceps, especially. Generally speaking, it is a good idea to strengthen your muscle by all means prior to your surgery, even three or four weeks prior to the surgery, as long as your knee pain is within control and it is allowing you to exercise without increasing or aggravating your pain.

I believe that as long as the patient’s pain is under control and they are well motivated, they should not have any trouble doing exercises prior to the surgery. And other than that, I don’t see any reasons why someone would not take the time to strengthen prior to the surgery.

In general, your pre-surgical status determines the functional outcome. The better your strength and better your range of motion deficits are, the better you are going to do after the surgery.

Also, research says that the amount of time that you have gone through a certain amount of knee range of motion deficits and pain also determines the outcomes after surgery. Patients generally lose their muscle strength after surgery at least by a grade, so it is recommended that they do a pre-surgical or a prehab for strengthening their quadriceps and hamstrings

I would say strengthening about three to four weeks prior to a surgery would be a good starting point to get some beneficial effects out of those strengthening exercises. Doing preparatory work two to three times a week prior to the surgery for at least three to four weeks is a general consensus for any strengthening program.

Geriatric patients typically are already weak in their muscles with the long duration of arthritis and decreased range of motion, Their muscle strength generally tends to be weaker. Geriatric populations are good candidates to start strengthening even prior to the surgery.

Any strengthening program prior to the surgery is going to be beneficial for the patient. If there is a tool like X10, why not use it to get your strengthening begin, as long as your pain is within a controllable limits and you’re able to handle it?

About The X10 Knee Recovery System™

Patients who have had knee surgeries in the past and have been either through a traditional home-based physical therapy, or a rehab, or have used a CPM machine on their previous knee surgeries, are truly able to compare the differences and the convenience of using the X10.

X10 patients are comfortable using this equipment. And also they are more compliant with their range of motion exercises. They are more motivated because they don’t have to wait for the therapist to say if they have increased range of motion for that day or not because they are able to look at the screen. And they also see the feeling in the knee. They are able to feel it and it becomes a further motivation for them to say, ‘okay, I can move so much today’. And then they compare themselves in terms of how much they are able to do day-by-day, and also maintaining the daily log.

They record these logs, so it forces them to look at their numbers. Either they are performing at the same level or they are improving. And automatically what happens, they want to beat their own numbers. And this allows for small incremental gains on a daily basis and even within the exercise sessions. So that is something really nice about having those patients engaged in their own therapy, and that’s great.

The initial focus on a knee therapy program would be to increase on the knee range of motion. And subsequently, or hand-and-hand I would say, strengthening goes along. So for a patient who is finishing two weeks or three weeks in home care and going to outpatient, they already have enough range of motion and now they are way ahead of most other people and they start into strengthening modules.

So thereby, range of motion and the joint stiffness and decreased range of motion affecting their function is all out of the way and these patients progress further in strengthening and implementing their functional status.

That’s where we saw our surprises coming in because patients were able to compare the differences and they felt better using the X10 rather than their previous experience with traditional physical therapy.

Patients who are on X10 are feeling more comfortable using the equipment itself and also are more willing to increase their range of motion and try out longer time durations. I would say that definitely this is a big factor in terms of patient perspective. Using a CPM and or any of the traditional physical therapy, they are more willing to participate, and they are more relaxed, and they are more comfortable using these X10 machines.

Editor’s note: We are so pleased to provide this interview with Physical Therapist Kishore Jeevanandam from Advanced Home Care in Michigan. Click here to visit the website of this great home care provider.

Two resources for you below. Both are email series that we created to help those who need some additional thinking for pre-surgery and post-surgery.