What is SPONK? What are the implications for your knee? Can it be treated without surgery? Let’s dig in.
What is SPONK?
SPONK stands for SPontaneous OsteoNecrosis of the Knee (1). Osteonecrosis is a bone disease where the bone dies off and then begins to lose its structural integrity. This loss of strong bone can cause the knee to become painful and allow arthritis to begin. This happens when the cartilage also begins to become damaged.
What Causes Spontaneous Osteonecrosis of the Knee?
It’s believed that SPONK (aka SONK) is usually caused by either chemical damage to the bone cells and/or too much force on one part of the knee. We all have wear and tear on our body and every night while we sleep our bodies repair these small injuries. This happens through stem cells that live in many tissues. However, as we age the ability of our body to repair gets less. When the stem cells in the bone are damaged or wear and tear on bone exceed repair, the bone cells can die off. That’s what happens to produce SPONK.
SPONK usually occurs in patients over 60 and it’s more commonly seen in women. 94% of the time the inside thigh bone (medial femoral condyle) is the affected area (4). The two most common possible causes include steroid medication use and alcoholism (5).
Another cause of SPONK is knee surgery. One way that the knee bones can be overloaded is by surgically removing a torn meniscus. In fact, there’s a whole group of SPONK patients who likely get SPONK due to meniscectomy surgeries (2). This is consistent with other research that shows that removing parts of the meniscus spacer can cause knee arthritis (3).
How is Osteonecrosis of the Knee Treated?
The short answer is that SPONK is frequently treated with surgery. However, non-surgical treatment usually takes the form of taking the weight off the area, managing the pain, and possibly using drugs meant to treat osteoporosis (bisphosphonates) (6). However, non-surgical care is often only used if the SPONK is caught early and the joint cartilage has yet to be impacted (meaning no arthritis caused by the SPONK).
There are several different types of surgery that can be attempted to preserve the joint. These a core decompression, an osteochondral allograft, or a high tibial osteotomy (HTO). Core decompression is a surgery where the SPONK lesion is drilled to try to improve blood supply and get fresh bone marrow cells into the area. An osteochondral allograft is the surgical implantation of cadaver bone into the SPONK lesion. Finally, HTO is cutting out a wedge of bone to realign the joint to remove weight from the area (7).
For patients with more advanced disease, the only option is usually joint replacement (8). This means removing all or part of the joint and replacing it with a prosthesis (artificial joint). This treatment is usually effective, but obviously this is a big procedure with possible serious side effects (10).
Can SPONK Be Treated without Surgery?
A new evolving area of osteonecrosis treatment is using the patient’s own bone marrow stem cells (bone marrow concentrate) to treat the disease (9). We have adapted this technique using both bone marrow concentrate (inside the US) and the patient’s own culture-expanded stem cells (outside the US). Let’s explore this new procedure.
In this procedure, known as Percutaneous Intraosseous Injection (PII), live x-ray guidance (fluoroscopy) is used to guide a needle into the SPONK lesion. Then, the patient’s own bone marrow concentrate or cultured stem cells are injected into the lesion. How well can this work?
Above are serial MRI images of an elderly patient with SPONK who had the PII procedure performed several times over the years. In these images the dead and dying bone is dark and the healthy bone is white. You can see the large areas of dead bone convert to healthy bone. Hence, this patient avoided all surgery.
The upshot? SPONK is a serious disease of the bone in the knee that used to frequently require surgery. However, in our experience, newer techniques are making the need for more invasive surgery like knee replacement obsolete. One such procedure is PII, which involves the direct injection of our own bone marrow cells into the lesion rather than a big surgery.
(1) Karim AR, Cherian JJ, Jauregui JJ, Pierce T, Mont MA. Osteonecrosis of the knee: review. Ann Transl Med. 2015;3(1):6. doi: 10.3978/j.issn.2305-5839.2014.11.13
(2) Bonadio MB, Demange MK. Post-meniscectomy spontaneous osteonecrosis of the knee (SPONK): etiology, clinical presentation and treatment. Ann Joint 2017;2:68. http://aoj.amegroups.com/article/view/3901/4535
(3) Longo UG, Ciuffreda M, Candela V1 Rizzello G, D’Andrea V, Mannering N, Berton A, Salvatore G, Denaro V. Knee Osteoarthritis after Arthroscopic Partial Meniscectomy: Prevalence and Progression of Radiographic Changes after 5 to 12 Years Compared with Contralateral Knee. J Knee Surg. 2019 May;32(5):407-413. doi: 10.1055/s-0038-1646926.
(4) al-Rowaih A, Björkengren A, Egund N, et al. Size of osteonecrosis of the knee. Clin Orthop Relat Res 1993;(287):68-75. https://www.ncbi.nlm.nih.gov/pubmed/8448962
(5) Mont MA, Baumgarten KM, Rifai A, et al. Atraumatic osteonecrosis of the knee. J Bone Joint Surg Am 2000;82:1279-90. https://www.ncbi.nlm.nih.gov/pubmed/11005519
(6) Kraenzlin ME, Graf C, Meier C, et al. Possible beneficial effect of bisphosphonates in osteonecrosis of the knee. Knee Surg Sports Traumatol Arthrosc 2010;18:1638-44. https://www.ncbi.nlm.nih.gov/pubmed/20376625
(7) Woehnl A, Naziri Q, Costa C, et al. Osteonecrosis of the knee. Orthopaedic Knowledge Online Journal 2012;10.
(8) Bonutti PM, Seyler TM, Delanois RE, et al. Osteonecrosis of the knee after laser or radiofrequency-assisted arthroscopy: treatment with minimally invasive knee arthroplasty. J Bone Joint Surg Am 2006;88:69-75. https://www.ncbi.nlm.nih.gov/pubmed/17079370
(9) Hernigou P, Beaujean F. Treatment of osteonecrosis with autologous bone marrow grafting. Clin Orthop Relat Res. 2002 Dec;(405):14-23. https://www.ncbi.nlm.nih.gov/pubmed/12461352
(10) Mulcahy H, Chew F. Current Concepts in Knee Replacement: Complications. American Journal of Roentgenology 2014 202:1, W76-W86. https://www.ajronline.org/doi/full/10.2214/AJR.13.11308