The Articular Intraosseous Cyst in Osteoarthritis: Subchondral Cysts and Traction Cysts
David Tallman, DC, NMD
Articular cysts are commonly encountered in the orthopedic practice. They can be sequelae to chronic sprains and strains, and can be a source of juxta-articular aberrancies. This article will describe the most common types of non-inflammatory degenerative articular intraosseous cysts found in the author’s orthopedic practice, which are subchondral cysts and traction cysts. A case example will also be included for each type.
A subchondral cyst is an intraosseous epiphyseal synovial fluid-filled void prevalent in osteoarthritis that may attain a diameter of 1-15 mm or more in size with the cyst’s longest axis usually along the coronal plane in the craniocaudal axis. The cysts appear in chronic osteoarthritis cases and tend to progress in size and number as the overlying cartilage surface thins. They are caused by a mortar and pestle-type grinding of a joint, similar to friction blisters on the volar surface of the hand and foot.
The underlying pathogenesis of most subchondral cysts is from chronically weakened stabilizing ligaments and musculature and/or cartilage buffer structural damage (menisci, labrum). This may lead to subclinical appendicular hypermobility and cartilage degradation from blunt trauma during ambulance under gravity and during unintentional mishaps that occur in everyday life that place concentrated hostile forces in areas on the articular surface of the joint. As the cartilage layer thins, the underlying epiphyseal layer forms areas of cysts with surrounding hyperdense margins of bone as compression and grinding forces the bone to remodel.
Subchondral cysts may also appear on the articulating surfaces of sesamoid bones such as the patella and opposing femoral surface. This type of subchondral cyst is caused by patellar maltracking and creates a situation where the normal articulating surface area has been substantially reduced and concentrated to a focal point of cartilage contact and eventual cartilage loss. Subchondral cysts are commonly the perpetrator of para-articular nonosseous cysts like Baker’s, popliteal, and other synovial cysts. A subchondral cyst may also cause parapatellar protuberance from excess synovial fluid; meniscus tears may also cause this condition. In the 9 years of the author’s orthopedic exclusive practice, subchondral cysts have been clinically observed and treated on the acromioclavicular, femoroacetabular, glenohumeral, interphalangeal, tibiotalar, radionavicular, carpometacarpal, femorotibial, tarsometatarsal, intertarsal, intercarpal and spinal joints.
Traction cysts are synovial fluid-filled voids found near tendon and ligament fibers’ subcortical attachment roots ranging from 1-10 mm. Traction cysts are usually unilobular, as opposed to subchondral cysts, which are commonly multilobular.
Traction cysts are usually caused by strains and sprains. The injuries may have occurred from a single or repetitive traumatic force on the fibers’ roots or may be one part of a complex appendicular dysfunction that involves aberrant pulling on the tendon from a weakened joint capsule, dysfunctional para-articular ligaments, or may be the result of downstream effects from a central lesion such as a chronic spinal disc problem. On the greater tuberosity of the humerus, traction cysts are common from supraspinatus and infraspinatus tendon tears and tendonitis. They are less commonly found on the subscapularis roots in the lesser tuberosity and on the posterior humeral head where the teres minor fibro-osseous roots are found. Traction cysts can also occur in the tibia and femur near the subcortical attachments of the anterior and posterior cruciate ligaments. A subclinical hypermobility probably contributes to the nonresolution of the traction cyst.
Subchondral and traction cysts are usually found on films ordered for a chronic complaint of joint pain. Many of the patients with subchondral cysts in the femorotibial and coxofemoral joints will have histories of joint pain and compensatory antalgic gait for months to years before presenting for treatment. Pain is usually the chief complaint, and a limited range of motion may be due to abnormal pressure on an intra-articular structure or from adjacent muscle spasm.
Proper imaging of the joint is useful to determine the existence and location of articular lesions. Intraosseous cysts are much easier to identify on a 3 Tesla MR scan than lower magnetic field units. If there is metal present near the joint, a CT scan in the axial, sagittal and coronal planes can be used to visualize and locate cysts. Plain films will usually not reveal the precise location and extent of articular cysts.
Plain Film Imaging
Femorotibial subchondral cysts smaller than 1 cm are difficult to identify on a radiograph, and only after seeing their location on an MRI can one appreciate them on an AP plain film unless they are well circumscribed by dense margins. Cysts larger than 1 cm can usually be seen with a trained eye on the AP view, but their location on the axial plane usually remains uncertain, as small cysts between the condyles are unlikely to be seen well on lateral views. However, in coxofemoral osteoarthritis, small subchondral cysts in the lateral acetabular area are easy to identify on an AP view due to the contrasting hyperdense calcium deposition usually present.
Subchondral cysts in the femoral head may become larger than 2 cm and can become quite numerous, giving a loculated appearance in chronic cases. A retrospective study on how the radiographic appearance of cysts correlated with labrum tears and cartilage appearance under arthroscopy demonstrated with a sensitivity of 80% and a specificity of 96.3% that a delamination cyst appearing on the frog leg view of the coxofemoral joint will be associated with a labrum tear. “A delamination cyst was defined as a cyst located in the anterolateral portion of the acetabulum either seen directly adjacent and medial to a lateral acetabular cyst or as an isolated larger cyst with an associated crack in the acetabular subchondral bone.”1
Magnetic Resonance Imaging
The typical subchondral cyst is hyperintense on the T2-weighted scan and hypointense on T1-weighted scans. They can usually be first visualized on the T2 coronal series and then precisely located on the axial and sagittal views. MR imaging can also be used to determine if the cyst is communicating with other cysts or another area of the joint. MR imaging also allows the practitioner to visualize bone marrow edema that has been highly associated with and seems to precede subchondral cyst formation.2
CT easily detects osseous defects with clarity and is useful for measuring large cysts and cyst communications that may precede a pathological fracture. CT can also be thin-sliced in selected areas for accuracy and can also be 3D rendered for spatial awareness.
Subchondral Cyst Case
A 68-year-old patient with chronic knee pain presented for evaluation and treatment. An MRI was ordered. After reviewing the films and performing an orthopedic exam, she was diagnosed with chronic sprains of the medial collateral, lateral collateral and coronary ligaments, medial meniscus degeneration and medial compartment cartilaginous degeneration. The MRI also demonstrated a large Baker’s cyst and a group of small loculated subchondral cysts in the posterior medial condyle. She had reported that the Baker’s cyst had been there for many years and periodically aspirated by different doctors. The Baker’s cyst was easily palpated and grossly seen with the patient in the prone position. Her knee also had a history of arthroscopic debridement and meniscus shaving. The knee ligaments were carefully treated by regenerative injection therapy. The subchondral cyst was determined as the source of the excess synovial fluid filling up the Baker’s cyst. The subchondral cyst was located in the posterior condyle of the femur and was directly needled using a technique the author has developed over the past 8 years of orthopedic practice. The subchondral cyst underwent 2 direct needling treatments over a 3-month time span. A follow-up MR study was ordered 1 month after the second treatment. The subchondral cyst was virtually nonexistent; the Baker’s cyst had reduced significantly and was non-palpable. Her visual analog scale (VAS) for pain was reduced in half of the initial score.
Traction Cyst Case
A 35-year-old patient presented with shoulder pain of 10 weeks duration. He reported a history of warehouse work that involved lifting boxes in an overhead fashion. He brought in an MRI that demonstrated supraspinatus and infraspinatus tendonitis, SLAP (superior labrum anterior-posterior) lesion, humeral chondral loss, and a large 1cm traction cyst where the supraspinatus insertion roots are. He was carefully treated on 6 occasions with a regenerative needling technique pioneered by the author. On follow-up MRI 4 months after the sixth treatment, the traction cyst was non-detectable and he was released with pain-free range of motion and unrestricted duties.
David A. Tallman, DC, NMD continued his family tradition at the Ohio State University for his undergraduate education. He then attended Texas Chiropractic College in Pasadena, TX where he received a Doctorate of Chiropractic with an internship focus on orthopedics and radiology. He then went on to graduate from Southwest College of Naturopathic Medicine in Tempe, AZ. He is a board-certified, licensed chiropractic physician (DC) and a licensed naturopathic medical doctor (NMD). Dr. Tallman is also the publisher of ND News & Review (NDNR) and the International Journal of Naturopathic Medicine (IntJNM). Dr. Tallman is a pioneer of regenerative injection therapy (RIT), his practice is devoted exclusively to prolotherapy/RIT. He has designed a unique and highly specialized method of needle manipulation over the years. He pursues up-to-date developments in the fields of orthopedic and sports medicine in the U.S. and Europe.
- Gdalevitch M, Smith K, Tanzer M. Delamination cysts: a predictor of acetabular cartilage delamination in hips with a labral tear. Clin Orthop Relat Res. 2009;467(4):985-991.
- Crema MD, Roemer F, Marra MD, Zhu Y, Javaid M, Guermazi A. MRI-detected bone marrow edema-like lesions are strongly associated with subchondral cysts in patients with or at risk for knee osteoarthritis: The MOST Study. Paper presented at: 94th Scientific Assembly and Annual Meeting of the Radiological Society of North America; November 30-December 5, 2008; Chicago, IL. Presentation No. SSA14-07.