Cartilage is tissue that struggles to heal on its own
When you go to a clinic with knee pain, you are told the cartilage has worn away. And usually the remark follows that cartilage, once worn, does not grow back.
The reason lies in the structure of cartilage. Blood vessels run through most tissues in our bodies, but articular cartilage has none. No blood vessels means no channel supplying oxygen and nutrients, and no route for the cells responsible for recovery to gather when injury occurs. It stands in contrast to skin, which bleeds, scabs over and heals when cut.
Cells are sparse as well. Cells make up a very small share of the total volume of cartilage; the rest is the matrix the cells have produced. Its load-bearing strength also comes from this matrix. So cartilage wearing away is less a matter of cells dying than a process of the matrix being consumed.
Degenerative arthritis is divided into stages
Arthritis does not appear out of nowhere one day. It goes through a process in which the cartilage gradually thins and the joint space narrows. The stages, from early to late, are divided according to what is seen on imaging.
In the early stage the cartilage is only slightly thinner and the pain is intermittent. In many cases it is uncomfortable only when walking for a long time or going down stairs. In the middle stage the range of cartilage damage widens and the joint space narrows noticeably. Pain becomes more frequent and swelling appears.
In the late stage almost no cartilage is left and bone contacts bone directly. At this stage, methods such as joint replacement are considered rather than attempting regeneration.
The reason for dividing into stages is that the available methods change. There has to be cartilage remaining for recovery to be attempted on that basis. That is the background to why regenerative approaches are raised mainly in the early and middle stages.
| Stage | Cartilage and symptoms | Direction considered |
|---|---|---|
| Early | Cartilage only slightly thinner, pain is intermittent | Regenerative approaches are raised on the basis of the remaining cartilage |
| Middle | Damage range widens and joint space narrows; pain is frequent and swelling appears | Regenerative approaches are raised on the basis of the remaining cartilage |
| Late | Almost no cartilage is left and bone contacts bone directly | Methods such as joint replacement are considered rather than attempting regeneration |
The methods tried so far
The oldest approach is to provide stimulation. Microfracture makes small holes in the bone beneath the cartilage so that bone marrow components seep out. It artificially draws in recovery resources that could not arrive because there are no blood vessels. However, the tissue that fills in this way is known not to be entirely identical in nature to the original cartilage.
Autologous cartilage transplantation takes cartilage from an area that does not bear weight and moves it to the damaged site. Its limitation is that a defect is created where the cartilage was taken.
More recently, approaches using stem cells have been added. Methods obtaining cells from bone marrow, from fat, and preparations cultured from cord blood have each been introduced along different routes. Rather than one replacing another, it is closer to the options having increased according to condition and stage.
What is the difference between bone marrow and fat?
The source of the cells differs. Bone marrow is harvested from inside the bone. The yield is not large and the harvesting process places a burden on the patient, but it is a long-studied route.
Fat is harvested through liposuction. Adipose tissue contains far more cells than bone marrow, so securing quantity is easier. The cell mixture obtained this way is called SVF.
Both share the fact that they are separated and used on the same day without culturing. Culturing requires time and a separate process, and it is also handled differently in law.
It is hard to declare one better than the other. Age, joint condition and the extent of the harvesting procedure a patient can handle all come into play. TheLINE Plastic Surgery performs knee joint SVF treatment using cells separated in our in-house dedicated laboratory.
The environment inside the joint matters too
Looking at cartilage alone does not yield an answer, because a joint is a structure in which cartilage, bone, ligaments, muscle and the synovial membrane move together.
Synovial fluid is the lubricating fluid that fills the joint. Since cartilage has no blood vessels, nutrients seep in through this fluid. When inflammation develops in the joint and the quality of the synovial fluid deteriorates, the remaining cartilage is also placed under strain. That is why calming the inflammation is mentioned first, before regeneration is attempted.
Leg alignment is involved as well. In a structure where weight is loaded to one side, as with bow legs, only the inner cartilage wears quickly. Without correcting the alignment, the same spot is consumed again.
Muscle is no different. If the muscles at the front of the thigh are weak, the impact the joint takes while walking is transmitted directly. That is the background to why strength training is recommended before and after the procedure.
There are standards set by law
Regenerative medicine is governed by the Act on Safety and Support of Advanced Regenerative Medicine and Advanced Biopharmaceuticals. The February 2024 amendment lifted the restriction on who could be included in clinical research and introduced a treatment system under which patients not participating in research can also receive cell therapy within the standards set by law. The amended act took effect in February 2025.
What matters is that it cannot be provided just anywhere. An institution must meet the personnel, facility and safety management standards required by law and be designated as a treatment institution by the Ministry of Health and Welfare. Areas classified as low risk, such as autologous cells, are open to hospital-level and clinic-level institutions as well.
Some methods have gone through a separate new medical technology assessment. Bone marrow-related procedures and PRP for knee osteoarthritis each received approval at different points in time. In your consultation, please check on what basis the procedure is being provided.
It helps to set expectations
The most common misunderstanding is the expectation that worn cartilage returns to its original state. As far as is currently known, recovery at that level has not been confirmed. What studies report is a direction of reduced pain and improved function, and even that varies greatly from person to person.
Stage is involved too. In the late stage, where almost no cartilage remains, there is not enough of a base on which to attempt regeneration. Age, body weight, activity level and knee alignment also affect the result.
Care after the procedure matters as well. Reducing body weight and strengthening the surrounding muscles are recommended alongside it as ways to lower the load on the joint. This means it is not a problem settled by a single procedure.
Care is also needed regarding anesthesia. The Korean Society of Anesthesiologists has issued an opinion that, for procedures using autologous adipose-derived stem cells, at least 6 hours of inpatient observation, and in some cases more than a day, is appropriate. Recovery may take longer in older patients or those with underlying conditions.
Frequently Asked Questions
Does worn cartilage return to its original state?
Recovery at that level has not been confirmed to date. What studies report is relief of pain and improvement of function, and individual differences are large. Setting expectations in advance is important.
Can it be attempted in late-stage arthritis?
At a stage where almost no cartilage remains, there is not enough of a base on which to attempt regeneration. In that case other methods such as joint replacement are considered, so we confirm the stage with imaging first.
Is one session enough?
It depends on your condition. In some cases we observe the course after one session, and in others it is repeated at intervals. Weight management and strength training are recommended after the procedure.
Are the effects weaker at an older age?
The number and activity of the cells obtained are known to change with age. However, individual differences are large, so we do not judge by age alone and look at the joint condition as well.
Is it covered by insurance?
It depends on the type of procedure and the approval route. In your consultation, please check on what basis the procedure is being provided and how the cost is calculated.
Is knee stem cell treatment available at TheLINE Plastic Surgery Clinic?
Yes. TheLINE is designated by the Ministry of Health and Welfare as an advanced regenerative medicine treatment institution, and we separate adipose SVF directly in the dedicated laboratory inside the clinic. However, suitability differs depending on the condition and stage of the joint, so we confirm this with imaging before deciding whether to proceed.
