How much motion should you have at any given point after surgery? Of course, you should speak to your surgeon about the specifics of your case. However I'd like to provide some general guidance on this subject.
During knee replacement surgery, the knee will be reconstructed using a metal and plastic prosthesis, and the ligaments balanced. At the conclusion of the operation, the knee will be able to fully extend (straighten) and fully flex (bend back). After surgery, although initially pain will prevent full range of motion, scar tissue has not had a chance to form. Most patients are able to move from full extension (0 degrees) to 90 degrees (foot flat on floor while sitting in normal chair) within 24-48 hours.
It is not uncommon for patients to lose a bit of motion around 7-10 days from surgery. This is a result of increased pain and swelling due to the inflammatory cascade. This inflammation peaks around 10 days from surgery. It is ok to go a bit easy on yourself during this time. Use plenty of ice and anti-inflammatory medication if it is allowed by your surgeon. But keep stretching. Do not allow yourself to lose full extension. This is crucial.
By the first postoperative visit around 2 weeks from surgery I would like to see a minimum of 0-90 degrees of motion.
By 6 weeks from surgery I would like to see 0-120 degrees minimum.
Patients may gain an additional 5-10 degrees of deep flexion over the course of the first year following surgery if they've gotten to 120 degrees by 6 weeks.
If these parameters are not met, other options are available. I begin asking patients to follow-up with me every other week or more to track their progress, to answer questions, and provide motivation and support. I understand that this process isn't always easy and is never fun. If inadequate range of motion isn't achieved by 6 weeks, I then recommend manipulation under anesthesia to break up scar tissue that has been allowed to form. This buys us some time and generally gets things back on track.
Uncommonly, a patient is unable to regain adequate range of motion in a reasonable period of time following total knee replacement surgery. When I observe a patient gradually falling behind with rehabilitation, I begin following them in my office more closely to provide guidance, and motivation. This can be a very frustrating situation for both the patient and surgeon.
I have previously written about the tissue planes in the knee that need to be encouraged to glide, and on some stretching techniques to accomplish this. My recommendations are based in part on the viscoelastic nature of these tissues.
I believe the quadriceps muscle can sometimes thwart a patients efforts to regain flexion. In the years prior to making the decision to proceed with knee replacement, a patient likely experienced episodes of giving-way or jolts of pain. The quadriceps would need to contract aggressively to prevent the knee from buckling. Additionally, many patients develop an abnormal, stiff-legged gait pattern which likely minimizes joint motion and pain. This quadriceps activity is likely subconscious, but by being repeated over a long period of time create neural pathways in the brain that are hard to break.
Postoperatively, the habitual quadriceps contraction in response to pain may make rehabilitation more challenging for these patients. I have developed this idea after hearing many patients explain how hard their physical therapist is pushing on their knee, and it simply will not bend. Ive been told the physical therapist is actually off the ground being supported by the patients knee. It sounds horrible. The only way for this to be possible within the first 6 weeks or so from surgery is for the patients quadriceps to be pushing back.
How can I be so certain? Because of my experience with manipulation under anesthesia. At around 6 weeks from surgery if a patient and I agree that their range of motion is not acceptable I perform this procedure.
A patient is briefly placed under anesthesia. I gently flex the knee while flexing the hip. Pressure is then progressively applied through the tibia and soft tissue releasing is felt and sometimes heard while this occurs. The goal is to re-establish the pre-patellar tissue plane (between the skin and the kneecap) and the suprapatellar pouch (between the quadriceps tendon and the femur).
Once this has been accomplished the knee will generally flex to 120-130 degrees under the force of gravity alone. This verifies that no more joint adhesions are obstructing motion.
So again, how do I know the quadriceps is fighting back? Because it only requires me to apply gentle pressure. Maybe 5-10 pounds of force. Worst case 20 pounds or so.
Based on this I recommend focusing on relaxing the quadriceps while stretching. Additionally, consider pre-fatiguing them. This is a technique where you would attempt to extend your knee while blocking it from moving (isometric quadriceps contraction) Then relax the quad and enter directly into the stretch. This can create significant gains. My experience has been most positive with prolonged, low force stretching as opposed to shorter, more aggressive stretches.
Relatively early manipulation of a stiff knee when necessary helps the vast majority of patients get back on track. By breaking up immature scar tissue it extends the rehabilitation window a bit. Patients still need to work hard on their stretching exercises on a daily basis, but by using this technique we can "catch them up," and help to ensure adequate function and pain relief.
Orthopedic Surgeon focused on the entire patient, not just a single joint.