What is osteonecrosis?
Osteonecrosis means bone death. The bone cells die due to blood flow reduction, lack of oxygen to the cells, and the bone begins to cause pain. This can occur in any bone, but it is commonly seen in the knee and hip joints. Pain can occur at rest and with weight bearing, unlike osteoarthritis pain that occurs mostly with weight bearing and is relieved with rest. Bone death can start off in a small area and can progress to a large area of bone. Sometimes the process stops, and the pain can go away. Initially, in the very early stages, the condition is not seen on x-ray. It can, however, be seen with MRI, in the very early phase. In these early pre-collapse phases, there are some potential non-joint replacement options that attempt to stop the progression of the process. As the osteonecrosis process worsens, the cartilage surface can collapse into the dead bone area causing more significant pain and disability. Once the process goes on to joint surface collapse, joint replacement is the usual solution to relieve the pain and restore function.
What is knee osteonecrosis?
Knee osteonecrosis is a bone death that occurs in the region of the knee, the location where the end of the femur and the top of the tibia meet, called the knee joint. Osteonecrosis is more commonly seen in the end of the femur (thigh bone), on the medial (inner side), called the medial femoral condyle. Knee osteonecrosis can also occur in the top of the tibia just below the surface called the tibial plateau. Osteonecrosis can occur across the entire end of either bone in the knee.
What are the symptoms of osteonecrosis of the knee?
- The most common symptom of knee osteonecrosis is pain in the knee. This pain can occur with weight bearing, but it can also occur when not weight bearing, like sitting or lying down in bed.
- The pain can be a dull aching pain, or a sharp stabbing pain.
- The presentation can include loss of motion.
- The presentation can include swelling in the knee joint.
What are the causes of knee osteonecrosis?
- Primary osteonecrosis is also called Spontaneously Osteonecrosis of the Knee or “SONK”. This is more commonly seen on the medial femoral condyle. It is usually thought to be secondary to ischemia or lack of oxygen and blood supply to the bone. It is also thought to be secondary to microfractures that cause swelling in the bone and then loss of blood flow and death. It is also more common over the age of 60 but can be seen younger as well.
- Pain is more commonly of sudden onset
- Commonly on the inner side of the knee (medial side)
- Secondary osteonecrosis of the knee is not as common. This form occurs more commonly in younger patients <50. It is thought to occur from corticosteroid use, excessive alcohol use/abuse, from sickle cell disease, from deep sea diving called Caisson disease, from tobacco use, from myeloproliferative disorders which are slow-growing blood cancers where bone marrow makes too many abnormal cells.
- Each of these in some way make blood flow difficult in the bone cells and cause ischemia leading to bone death.
- Pain is more commonly slower in onset
- It is also commonly seen in both knees, and can be seen in other bones in the body
- Osteonecrosis After a Knee Arthroscopy is the third cause of this condition. This can present 1-2 months after a knee arthroscopy for a meniscus tear or cartilage procedure and is associated with a sudden onset of pain at this interval after surgery. This is a very infrequent cause of osteonecrosis.
What makes someone a knee osteonecrosis specialist?
- An osteonecrosis specialist is commonly an orthopaedic surgeon that specializes in joint replacement.
- These doctors are keen at diagnosing and examining patients with knee pain complaints.
- Surgeons that see many patients with knee pain will commonly see osteonecrosis in their daily job and confirm the diagnosis with xrays and MRI studies.
- A specialist should also know how to manage the different stages of osteonecrosis. This means treating early stages without surgery and later stages with the appropriate surgery.
Can you leave knee osteonecrosis untreated?
- You can treat osteonecrosis of the knee conservatively in the early stages. This means protecting the joint from excessive pressure by using canes, crutches, walkers when walking. It also means using NSAID medications and is some cases prescription medications.
- In the later stages the pain is generally debilitating and patients seek out treatment to relieve their pain.
How do you treat osteonecrosis of the knee non-surgically?
- In the early pre-collapse stages, patients can consider protecting the joint from excessive pressure by using canes, crutches, or walkers when walking.
- There has also been evidence that using NSAIDs and is some cases prescription medications called Bisphosphonates can be effective. You need to discuss this with your doctor to see what options might be beneficial for your case.
How do you treat osteonecrosis surgically?
- Treating osteonecrosis surgically depends on the stage of the disease, how extensive it is, and knowing the cause of the osteonecrosis.
- Early in the process a “core decompression procedure” can be used to drill into the bone area that has died, attempting to bring new blood supply to the region.
- Sometimes cutting out the bad zone and inserting a cadaver bone with cartilage into the bad area can work. This is called an “osteochondral allograft”.
- Sometimes cutting the bone and changing the loading angle to take pressure off one side of the knee joint that is affected can help. This is called an “osteotomy”. This requires cutting the bone, changing the angle, and holding it with a plate and screws until it heals over a couple months.
- Partial Knee Replacement is a surgical procedure that places new surfaces on the end of the bones on one side of the knee joint that is affected by the osteonecrosis.
- Total Knee Replacement is a surgical procedure that places new surfaces on all the surfaces on the end of the bones of the knee joint because the disease is more extensive than in cases that can be fixed with just a partial knee replacement.
What is a Partial Knee replacement?
- A partial knee replacement is a surgical procedure that places a new artificial surface on the ends of the bones of the knee joint where the original cartilage surface is damaged or worn away or in these cases, osteonecrotic.
- The knee joint has 3 “compartments”. The medial, lateral and patellofemoral compartments. In osteonecrosis, the compartments affected are mostly the medial compartment and sometimes the lateral compartment. The patellofemoral compartment is not commonly affected in isolation with osteonecrosis.
- It is called a partial knee replacement because we replace the surface of the bone on only one or two of the 3 parts of the knee joint, leaving the healthy compartments and ligaments alone to function normally.
- A partial knee replacement is made of metal and plastic parts called “implants”. The metal parts are usually cobalt chrome and/or titanium, and the plastic part, called the “insert” or “bearing”, is ultra-high molecular weight polyethylene.
- The parts are usually attached to the bone using a bone cement, and sometimes they can be attached without cement. In osteonecrosis cases, bone cement is the preferred attachment.
- There are several terms that are used interchangeably to describe partial knee replacement. The synonymous names include knee replacement, knee resurfacing and knee arthroplasty.
What is the typical follow-up care like for a Partial Knee replacement surgery for osteonecrosis?
- I perform my Mako Robotic Partial Knee Replacements as an outpatient procedure.
- Patients return to the office the day after surgery to have their dressing changed and to address any issues right away.
- Patients can return home if they are traveling to New York for their surgery generally in 3-4 days if needed.
- We have a great team of therapist if you stay in the area.
- We provide several means by which to stay in contact after your surgery including office visits, text, mobile phone, email, video conferencing.
- We maintain close contact with you in the early recovery phase to make sure you feel comfortable and all your concerns are addressed.
- We like to see you back if possible, in 4-6 weeks after surgery, or check in via any of our contact means along with photos of your leg during the healing process.
- 6 months after surgery is another check-in milestone at which time we like to hear from you.
- Annually we like to have an x-ray of the operative knee to ensure everything is as desired.
What is a total knee replacement?
- A total knee replacement is a surgical procedure that places new artificial surfaces on the ends of the bones of the knee joint where the original cartilage surface is damaged, worn away, or in the case of osteonecrosis, the bone has died, and the cartilage has collapsed.
- The knee joint has 3 compartments, the medial on the inside, the lateral on the outside, and patellofemoral compartments which is the kneecap and the front of the thigh bone.
- A total knee replacement replaces the surface of all 3 compartments of the knee joint with metal and plastic parts called “implants”.
- The metal parts are usually cobalt chrome and/or titanium, and the plastic part, called the “insert” or “bearing”, is ultra-high molecular weight polyethylene.
- The parts are usually attached to the bone using a bone cement, and sometimes they can be attached without cement which is called cementless.
- Cemented implants are preferred in the case of osteonecrosis. These patients have a blood supply to the bone that is not healthy to begin with. Therefore, using an implant that relies on the bone growing into the implant in this situation, like a cementless implant does, is not optimal.
What is the typical follow-up care like for a Total Knee replacement surgery for osteonecrosis?
- The follow-up care for total knee replacement starts in the hospital.
- Patients are managed by the medical and surgical teams in the hospital during their stay.
- Physical therapists are a key part of getting patients up and mobile after surgery. They participate in the care at the hospital and for several months after surgery in rehabilitation facilities, during home physical therapy, and in outpatient therapy programs.
- Early in the follow-up care for total knee replacement patients the focus is on achieving good wound healing and avoidance of infection. This can be optimized in many ways.
- Optimal surgical wound closure and gentle handling of the skin and tissues during the surgery is critical.
- The use of skin adhesives can seal the incision after the deep and superficial suturing is complete. These skin adhesives can keep out bacteria, allow for showering right after surgery, and avoid having painful staples removed that also leave unpleasant scaring.
- Good nutrition & protein intake, supplementation with Vitamin C, and avoidance of smoking are important in wound healing optimization. Swelling management is a critical part of proper care following total knee replacement.
- Keeping the leg elevated when not walking or exercising after surgery for the first 2-3 weeks significantly reduces potential leg swelling.
- The use of cold therapy devices helps with wound healing by reducing the pressure on the incision which allows the tissues to knit together faster and better.
- The use of compression sleeves can also help with swelling reduction as long as they are comfortable and are checked by the patient regularly so as not to slide down on the leg, which can cause local constriction and tissue injury.
What is the after-care for surgical treatment?
- Office follow-up visits with the surgeon early on are for wound evaluation, swelling evaluation, range of motion checks, pain control discussions and to listen to and help with any issues that have arisen since the surgery.
- As the weeks and months pass, follow-up becomes more focused on function, strength, and motion.
- Implant evaluations are done at follow-up intervals by examining the patients range of motion, stability and by obtaining x-rays to evaluate the status of the bone implant interfaces, implant insert thickness and alignment.
- As the years go by, interval examinations are done to evaluate for implant insert plastic wear and metal bone attachment to ensure the implants are stable and prepare for future intervention if the parts over time begin to wear down or loosen.