Knee injuries are among the most common musculoskeletal injuries, typically resulting from participation in contact sports or slip-and-fall or motor vehicle accidents that result in significant, forceful impact to the knee. In fact, among adolescent athletes, the knee is the joint that’s most commonly injured, and knee injuries among young athletes account for about 2.5 million emergency room visits each year [1]. Unlike knee surgeries that have long recovery periods and are associated with scarring, stem cell therapy is a well-tolerated treatment that uses the body’s natural capacity to heal itself. Moreover, the anti-inflammatory factors secreted from stem cells, particularly mesenchymal stem cells, are known to reduce inflammation at the affected area.


The knee joint comprises three bones – the thigh bone, shin bone and kneecap, or patella – as well as tendons, ligaments, cartilage, nerves and blood vessels. Injury to the knee can affect one component, but often affects more than one, making healing and recovery a complex process.

The most common knee injuries include [2].

  • Fractures
  • Dislocation
  • Anterior cruciate ligament (ACL) injuries
  • Posterior cruciate ligament injuries
  • Collateral ligament injuries
  • Meniscal tears
  • Tendon tears
  • Osteoarthritis
  • Patellar tendinitis

Injuries can also affect the cartilage. The cartilage in the knee protects the bony surfaces and prevents friction, enabling pain-free motion of the joint. In the knee, the cartilage is called the meniscus, and it has the additional role of distributing the weight of the body across the joint surface during motion. The meniscus has a very limited blood supply, which means when injury damages the meniscus, the healing process is impaired or slowed. Meniscus injuries are common among professional athletes, and surgery is often required to correct damage. Unfortunately, surgery to repair the meniscus often leads to cartilage deterioration and osteoarthritis [3].

Injuries to the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) are also common among athletes, especially in sports that require twisting or repetitive pressure on the joint [4].

The most common symptoms of knee injury are swelling, pain or tenderness around the joint and pain when placing pressure on the joint [5]. Many knee injuries, especially those affecting the ligaments, can result in feelings of instability. Other injuries can cause your knee to feel as if it’s “catching” or locking up during motion, or a clicking or crunching noise or grinding sensation may be present. During the injury itself and depending on the type of injury, a “popping” noise may be heard as ligaments snap or the bones of the joint move out of alignment.


The type of treatment provided for knee injuries depends on what kind of injury has occurred. For more mild sprains or strains, rest, ice, compression and elevation (RICE) can help speed recovery, at least in its earliest stages. Nonsteroidal anti-inflammatory drugs (NSAIDs) can help reduce pain and inflammation, and steroid injections can aid in recovery when NSAIDs aren’t enough. Many knee injuries – even mild ones – require physical or occupational (or sports) therapy to regain strength, flexibility and range of motion.

Severe injuries including tears to the meniscus, ligaments and tendons as well as fractures require surgery to repair. Some surgery, including cartilage grafting procedures, can be done arthroscopically, using a small incision and special instruments to promote faster recovery and healing after surgery, but others require large incisions or “open” surgical techniques to gain more access to the area. For severe injury, knee replacement surgery is an option.

Following surgery, long periods of therapy are often required to help return the knee to full function. In some cases, full function cannot be restored, and many patients go on to develop arthritis that can become debilitating.

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Because of their regenerative and anti-inflammatory benefits, stem cells have been evaluated in the management of all sorts of orthopedic injuries, including knee injuries. Most knee injury studies examining the use of stem cells have focused on damage to the cartilage or ligaments (or both) or the subsequent development of osteoarthritis that can plague joints with prior injuries.

In the U.S., today’s stem cell studies focus on the use of so-called mesenchymal, or adult, stem cells derived from fat, bone marrow or blood rather than the use of embryonic stem cells from umbilical cords. Like embryonic stem cells, adult stem cells are multipotent, which means they can differentiate into different types of cells, theoretically making them an ideal choice for management strategies that seek to replace tissues damaged by disease or injury. Stem cells also help mediate inflammatory responses that can play a major role in both injury and disease, especially in diseases like osteoarthritis.

Stem cells’ regenerative benefits have been evaluated extensively in recent studies of knee cartilage injuries. Although traditionally cartilage grafting has been used to replace smaller areas of damaged cartilage, grafting has two primary disadvantages: First, cartilage has a very limited blood supply, which means grafts can have a difficult time adjusting to a new location, especially when subjected to the considerable forces exerted on the knee joint. And second, a graft leaves a second injured spot at the donor site which can also begin to degenerate and even become arthritic. In addition, cartilage grafting is only an option in patients who have an adequate supply of healthy cartilage elsewhere in the body.

Although some studies have examined the use of stem cells in creating cartilage grafts outside the body, most current research is focused on using injections of cells to promote tissue regeneration at the site of the injury [3]. Several recent studies have found injection of adult stem cells is a safe and effective method of promoting cartilage regeneration in damaged knees, resulting in increased volume of knee cartilage, decreasing lesion size and reducing pain in people with damaged cartilage and meniscal tears. [6][7][8]

Additional research has demonstrated the benefits of using adult stem cell injections in managing knee osteoarthritis, a common side effect of knee injuries, by decreasing pain and improving joint function. [9]

Knee ligament injuries involving ligament, cartilage and meniscus damage are very common. However, due to the low vascularity of these tissues, the process of repair and regeneration is difficult. Therefore, by delivering autologous or allogeneic stem cells into the damaged tissue, it is possible to promote natural healing after knee ligament injuries. Emerging studies have demonstrated the use of bone marrow or adipose derived stem cells to augment repair or torn or damaged ligaments, a common cause of long-term debility in people with knee injuries. Most studies have focused on stem cells’ effects in promoting growth factors that can speed healing as well as their ability to slow inflammatory processes so tissue repair can proceed more quickly and with greater long-term success. [10][11]

In addition, platelet-rich plasma (PRP) therapy has been used by itself or in conjunction with stem cell therapy to enhance healing. Platelet-rich plasma is obtained from the patient’s blood by concentrating the platelet cells. It is known that high concentration of platelets is required to stimulate healing mechanisms in the body.

Unlike knee surgeries that have long recovery periods and are associated with scarring, research thus far suggests that stem cell therapy is a well-tolerated treatment. Moreover, the anti-inflammatory factors secreted from stem cells, particularly mesenchymal stem cells, are known to reduce inflammation that may be the source of pain.

Suggested Reading:

  1. Gage, BE, Mcilvain, NM, Collins, CL, Fields, SK, Comstock, RD. Epidemiology of 66 Million Knee Injuries Presenting to United States Emergency Departments From 1999 Through 2008. Academic Emergency Medicine. 2012;19(4):378-385. doi:10.1111/j.1553-2712.2012.01315.x.
  2. Common knee injuries . the American Academy of Orthopaedic Surgeons. Available at:
  3. Stem cells and sports medicine: an overview. EuroStemCell. Available at:
  4. Anterior Cruciate Ligament (ACL) Injuries. the American Academy of Orthopaedic Surgeons. Available at:
  5. Posterior cruciate ligament injury. Mayo Clinic. Available at: Mayo Clinic.
  6. Centeno, CJ, Busse, D, Keohan, C, Freeman, MM. Increased knee cartilage volume in degenerative joint disease using percutaneously implanted, autologous mesenchymal stem cells, platelet lysate and dexamethasone. Medical Science Monitor. 2008. Available at:
  7. Jaewoo Pak, Jung Hun Lee, and Sang Hee Lee, “Regenerative Repair of Damaged Meniscus with Autologous Adipose Tissue-Derived Stem Cells,” BioMed Research International, vol. 2014, Article ID 436029, 10 pages, 2014. doi:10.1155/2014/436029
  8. Dhinsa, BS, Adesida, AB. Current Clinical Therapies for Cartilage Repair, their Limitation and the Role of Stem Cells. Current Stem Cell Research & Therapy. 2012;7(2):143-148. doi:10.2174/157488812799219009.
  9. Koh, Y, Jo, S, Kwon, O, et al. Mesenchymal Stem Cell Injections Improve Symptoms of Knee Osteoarthritis. Arthroscopy: The Journal of Arthroscopic & Related Surgery. 2013;29(4):748-755. doi:10.1016/j.arthro.2012.11.017.
  10. Kushida, T, Iida, H. Bone marrow cell transplantation efficiently repairs tendon and ligament injuries. Frontiers in Cell and Developmental Biology. 2014;2. doi:10.3389/fcell.2014.00027.
  11. Hoffmann, A, Gross, G. Tendon and ligament engineering in the adult organism: mesenchymal stem cells and gene-therapeutic approaches. International Orthopaedics. 2007;31(6):791-797. doi:10.1007/s00264-007-0395-9.

Combination of Intra-Articular and Intraosseous Injections of Platelet Rich Plasma for Severe KneeOsteoarthritis: A Pilot Study.

Sánchez M, Delgado D, Sánchez P, Muiños-López E, Paiva B, Granero-Moltó F, Prósper F, Pompei O, Pérez JC, Azofra J, Padilla S, Fiz N.

Biomed Res Int. 2016;2016:4868613. doi: 10.1155/2016/4868613.

Adipose Mesenchymal Stromal Cell-Based Therapy for Severe Osteoarthritis of the Knee: A Phase I Dose-Escalation Trial.

Pers YM, Rackwitz L, Ferreira R, Pullig O, Delfour C, Barry F, Sensebe L, Casteilla L, Fleury S, Bourin P, Noël D, Canovas F, Cyteval C, Lisignoli G, Schrauth J, Haddad D, Domergue S, Noeth U, Jorgensen C; ADIPOA Consortium..

Stem Cells Transl Med. 2016 Jul;5(7):847-56. doi: 10.5966/sctm.2015-0245

Intra-articular treatment of knee osteoarthritis: from anti-inflammatories to products of regenerative medicine.

Richards MM, Maxwell JS, Weng L, Angelos MG, Golzarian J.

Phys Sportsmed. 2016;44(2):101-8. doi: 10.1080/00913847.2016.1168272. Review.

Stem cell therapy: a promising biological strategy for tendon-bone healing after anterior cruciate ligament reconstruction.

Hao ZC, Wang SZ, Zhang XJ, Lu J.

Cell Prolif. 2016 Apr;49(2):154-62. doi: 10.1111/cpr.12242. Review.

Adipose derived mesenchymal stem cell therapy in the treatment of isolated knee chondral lesions: design of a randomised controlled pilot study comparing arthroscopic microfracture versus arthroscopic microfracture combined with postoperative mesenchymal stem cell injections.

Freitag J, Ford J, Bates D, Boyd R, Hahne A, Wang Y, Cicuttini F, Huguenin L, Norsworthy C, Shah K.

BMJ Open. 2015 Dec 18;5(12):e009332. doi: 10.1136/bmjopen-2015-009332.

Adipose-Derived Mesenchymal Stem Cells With Microfracture Versus Microfracture Alone: 2-Year Follow-up of a Prospective Randomized Trial.

Koh YG, Kwon OR, Kim YS, Choi YJ, Tak DH.

Arthroscopy. 2016 Jan;32(1):97-109. doi: 10.1016/j.arthro.2015.09.010.

Mesenchymal Stem Cells for Enhancing Biologic Healing after Anterior Cruciate Ligament Injuries.

Jang KM, Lim HC, Bae JH.

Curr Stem Cell Res Ther. 2015;10(6):535-47. Review.

Mesenchymal stem cell therapy for knee osteoarthritis: 5 years follow-up of three patients.

Davatchi F, Sadeghi Abdollahi B, Mohyeddin M, Nikbin B.

Int J Rheum Dis. 2016 Mar;19(3):219-25. doi: 10.1111/1756-185X.12670.

Efficacy of mesenchymal stem cells injection for the management of knee osteoarthritis: a systematic review and meta-analysis.

Xia P, Wang X, Lin Q, Li X.

Int Orthop. 2015 Dec;39(12):2363-72. doi: 10.1007/s00264-015-2785-8. Review

Meniscus repair using mesenchymal stem cells – a comprehensive review.

Yu H, Adesida AB, Jomha NM.

Stem Cell Res Ther. 2015 Apr 30;6:86. doi: 10.1186/s13287-015-0077-2. Review.

Treatment of Knee Osteoarthritis With Allogeneic Bone Marrow Mesenchymal Stem Cells: A Randomized Controlled Trial.

Vega A, Martín-Ferrero MA, Del Canto F, Alberca M, García V, Munar A, Orozco L, Soler R, Fuertes JJ, Huguet M, Sánchez A, García-Sancho J.

Transplantation. 2015 Aug;99(8):1681-90. doi: 10.1097/TP.0000000000000678.

Actual results may vary. The statements are not intended to imply that the results would be the same or similar for each patient. Each patient is unique and no particular result or outcome can be predicted or guaranteed. The statements in this website have not been evaluated by the Food and Drug Administration. Some of these procedures may be considered experimental. These procedures are not intended to diagnose, treat, cure or prevent any disease. The use of stem cells is not approved by the Food and Drug Administration to combat aging or to prevent, treat, cure or mitigate any disease or medical condition mentioned, cited or described in this website. The science of treatment with stem cells is in its early stages and stem cell treatments are not considered to be the standard of care for any medical condition, ailment, illness or disease. There could be significant and unknown risks associated with stem cell treatments, as long-term studies have not been performed.