Total knee replacement has become a very common elective surgery, and patients are often amazed at how quickly they can get back to "normal" life after surgery. Within hours of their surgery, my patients are often able to begin walking with the assistance of a physical therapist and a walker. While most of my total joint replacement patients can be discharged to home within 48 hours, many are stable for discharge within 24 hours of surgery.
In spite of the anticipated rapid early recovery following total knee replacement, there is still a significant healing process that must occur. This healing process progresses through an inflammatory cascade and continues for over a year from surgery. It is this inflammatory cascade that requires a dedicated stretching regimen to ensure optimal knee range of motion following surgery.
Many patients are concerned that their knee feels warm, and may appear swollen and/or pink in the early post-operative period following knee replacement. In the vast majority of cases, this is normal and an anticipated part of the recovery period. Of course, if there is ever a concern, you should always discuss this with your orthopedic surgeon. Why does this happen? Basically, the body increases blood flow to the knee region to support the healing process. This increased blood flow results in the warmth, swelling and redness often experienced by the patient.
As the healing process progresses, the warmth, swelling and redness dissipate. The warmth can take 6 months or longer to resolve. Swelling and redness generally resolve within a few weeks of surgery.
A bone scan is a nuclear medicine radiological study that reveals bone metabolic activity. It will light up in areas that are irritated such as fractures, stress reactions, tumors and arthritic joints. If a bone scan is performed within 2 years of a total joint replacement, it will show increased bone metabolic activity adjacent to the relatively new prosthesis (even when the prosthesis is functioning properly). This is further indication that the healing process following joint replacement progresses over a very long period of time. Thankfully, the replaced joint usually feels great, long before the body has fully recovered.
So, after total knee replacement you can monitor the healing process by feeling the skin overlying your knee. As your skin gradually cools off, month-by-month, you know the healing process is winding down.
Please note: Severe swelling/redness, drainage from the wound, increasing pain, and/or loss of range-of-motion should not be assumed to be normal. If there is any concern, you need to be evaluated by your orthopedic surgeon immediately.
So you finally decided to have your arthritic knee replaced. You got through the surgery just fine. As expected, you had some surgical pain, but almost immediately you realized that your arthritic pain was gone. Awesome! Things seemed to be going very nicely, and now you are home...
Your knee may begin feeling tight and warm. This is normal and expected. Healing occurs in part through an inflammatory process. Inflammation shows up as swelling, warmth, and pain. You have been told to stretch, but may be questioning this recommendation now. You may be concerned that because it hurts you could be damaging yourself or your new knee. This is a very common concern. Please resist the urge to stop stretching.
The knee is a complex joint. There several moving parts and potential spaces (otherwise known as tissue planes). During total knee replacement these parts are moved around , the tissue planes are opened. I think it makes sense to patients when they have some pain after surgery. But as the wound is healing on the outside, why does it feel like things are getting worse on the inside?
As the healing process proceeds, the tissue planes that have been opened begin sticking together. Gradually adhesions, or scar tissue, may form between these planes preventing them from gliding properly. Initially this scar tissue is weak, but it will get stronger every day. For this reason, there is some urgency to regain range of motion as soon as possible. This is because after about 6 weeks or so from surgery this scar tissue becomes strong enough that a patient is unlikely to be able to stretch it out any more. The range of motion you have achieved at this point will be how far your knee will move permanently...without additional intervention.
To better understand knee range of motion lets begin with a couple of definitions. Flexion of the knee means bending. When you sit in a chair and your feet are flat on the floor, your knee is bent, or flexed. Extension of the knee means straightened. When you stand up and your knee is straight it is extended.
Now lets discuss these tissue planes a bit.
The skin must be able to slide over the kneecap (patella). The body achieves this by only loosely attaching the skin to the patella. This loose connective tissue allows motion to occur. Under abnormal conditions, fluid can collect here and create swelling. A potential space such as this is referred to as a bursa. The loose connective tissue found here is called bursal tissue. The specific space, or tissue plane, between the skin and the kneecap is called the pre-patellar bursa. It is shown in purple in my sketch.
The kneecap (patella) is embedded within the tendon that attaches your thigh muscles (quadriceps) to your shin bone (tibia). A tendon is the tissue that attaches muscle to bone. The quadriceps tendon must be able to slide relative to the thigh bone (femur). The area above the patella shown in my sketch as orange is called the supra-patellar pouch.
If either of these tissue planes sticks together, the knee will not be able to bend completely.
In the back of the knee there is a sheet of tissue called the posterior capsule. This is green in my sketch. This tissue is irritated during surgery and will gradually tighten as it heals. If this is allowed to happen, the knee will not fully extend.
So, how do you prevent a stiff total knee? It is not by walking around a lot. It is not by cycling the knee back and forth a lot. It is by gently and progressively stretching. Even though it hurts. The longer you are from surgery, the longer these stretching sessions must be because the scar tissue becomes stronger each day. Gentle progressive stretching works by taking advantage of the viscoelastic nature of biologic tissues.
My basic recommendations:
Future posts will further develop these concepts.
Orthopedic Surgeon focused on the entire patient, not just a single joint.