OCD is identified most commonly in skeletally immature adolescents (whose growth plates have not closed), occurring in 15 to 30 people per 100,000 every year. The symptoms of osteochondritis dissecans are pain and swelling of the affected joint, catching and locking on movement and a restriction in the range of motion. These symptoms characterize many knee conditions and may have a broad range of other causes, making OCD relatively hard to clinically diagnose. To confirm the diagnosis, X-rays, CT scans and often magnetic resonance imaging (MRI) are usually required. OCD is classified by the progression of the disease in stages (I, II, III or IV), and may be treated accordingly with a form of articular cartilage repair.
König coined the term osteochondritis dissecans in 1887, describing it as an inflammation of the bone-cartilage interface. Other terms have been associated with OCD in the literature, including osteochondral (pertaining to cartilage) fracture, osteonecrosis, accessory ossification center, osteochondrosis, and hereditary epiphyseal dysplasia. Osteochondritis dissecans may affect several other species of animals; dogs, especially the German Shepherd, are the most commonly affected.
The Anderson MRI staging of osteochondral lesions is as follows:
Stages I and II are stable lesions, while stages III and IV describe unstable lesions in which not only is the cartilage breached, but synovial fluid exists between the fragment and underlying bone.
The Cheng arthroscopic staging of osteochondral lesions is as follows:
Patients with OCD complain of activity-related pain that develops gradually. Subjective complaints usually consist of mechanical symptoms, including pain, swelling, catching, locking, and "giving way"; the primary presenting symptom may be a restriction in the range of movement. Symptoms typically present themselves within the first stage of OCD (I), however the onset of stage II is usually within months and the disease progresses rapidly. This quick progression of OCD, combined with a set of symptoms similar of other causes (sprains, strains), leads to a late diagnosis and subsequently further damage. Physical examination typically reveals an effusion, tenderness, and crepitus. The tenderness may be diffuse initially but often changes to well-defined focal tenderness as the lesion progresses. Acute osteochondral fracture has a similar presentation, but is usually associated with a fatty hemarthrosis. Although there is no significant pathologic gait or characteristic alignment abnormality associated with OCD, the patient may walk with the involved leg externally rotated in an attempt to avoid tibial spine impingement on the lateral aspect of the medial condyle femur.
Trauma, rather than avascular necrosis, is thought to be the factor which localizes and determines the development of osteochondritis dissecans in juveniles. In the adult group of cases trauma is thought to be the main or perhaps the sole factor in determining the onset of osteochondritis dissecans. The trauma may be endogenous and/or exogenous. Interestingly, the incidence of overuse injuries in young athletes is on the rise and accounts for a significant number of visits to the primary care office; this reinforces the theory that OCD may be associated with increased participation in sports and subsequent trauma.
OCD occurs when a loose piece of bone or cartilage partially (or fully) separates from the end of the bone, often because of a loss of blood supply (osteonecrosis) and insufficient amounts of calcium. The loose piece may stay in place or slide around making the joint stiff and unstable. OCD in humans most commonly affects the knees or ankles, but can also affect other joints such as the elbow.
Four minor stages of OCD have been identified after trauma, including revascularization and formation of granulation (scar) tissue, absorption of necrotic fragments, intertrabecular osteoid deposition, and remodeling of new bone. With delay in the revascularization stage, an OCD lesion develops. OCD lesions may lead to articular-surface irregularities, which can cause degenerative arthritic changes.
The possibility of microtrauma contributing to OCD underscores the importance of evaluating biomechanical forces at the knee during the physical examination. An evaluation of the alignment and rotation of all major joints in the involved extremity; as well as extrinsic and intrinsic abnormalities of the joint, including joint laxity, should be considered.
Plain radiographs show lucency of the ossification front, representing growth inhibition, in young patients. In older adolescents, the OCD lesion frequently appears as a well-circumscribed area of sclerotic subchondral bone with a radiolucent line between the defect and the epiphysis. The apparent size of the lesion depends on its location on the condyle and on the amount of knee flexion used. By viewing the lateral (side) radiograph, Harding described a method to identify the most common site of an OCD lesion. Cahill and Berg described a method to record the location of OCD based on radiographs by plotting the lesion with coordinates; the letters A--C are used for the lateral view, and the numbers 1--5 are used for the anteroposterior view (dividing both condyles into two equal halves and a separate area over the intercondylar notch).
Magnetic resonance imaging is useful for staging OCD lesions, evaluating the integrity of the joint surface, and distinguishing normal variants from OCD by showing bone and cartilage edema in the area of the irregularity. MRI provides information regarding features of the Articular Cartilage and underlying subchondral (below cartilage) bone, including edema, fractures, fluid interfaces, articular surface integrity, and fragment displacement. High signal at the fragment interface is seen in active lesions, which is considered to be potentially unstable or to have current or recent microfractures. MRI and arthroscopy have been reported to have a close correlation, while MRI and plain radiographs have been shown to have a poorer correlation.
CT (computed tomography) scans and technetium bone scintigraphy are also sometimes used to monitor the progress of treatment. Unlike plain radiographs (X-rays), CT scans, along with MRI's, can show the exact location and extent of the lesion. Technetium bone scintigraphy can detect osteoblastic activity, regional blood flow, and the amount of osseous uptake, which seem to be correlated to the potential amount of healing possible in the osteochondral fragment.
Patients with OCD of the knee are immobilized for four to six weeks in a cylinder cast in extension to remove shear stress from the involved area, however, they are permitted to walk with weight bearing as tolerated. If the plain radiographs taken three months after the start of non-operative therapy reveal that the lesion has healed, then a gradual return to activities is instituted. Patients with some component of healing demonstrated by increased radiodensity in the subchondral region, or those patients whose lesions are unchanged, are candidates to repeat the above described three-month protocol until healing is noted.
Using pluripotential cells from the marrow elements was established with the first surgical debridement of an OCD lesion in 1946 by Magnusson. The recruited cells differentiate mostly into fibrocartilage, which is principally type I collagen and rarely types II, VI, and IX (hyaline types). While small lesions can be effectively resurfaced, the repair tissue typically has less strength than normal hyaline Articular Cartilage and must be protected from high impact loading for 6 to 12 months. The results for large lesions usually diminish over time due to the decreased resilience, stiffness, and poor wear characteristics of the fibrocartilage.
In attempts to address the weaker structure of the reparative fibrocartilage, new techniques have been designed to fill the defect with tissue that more closely simulates normal hyaline articular cartilage. One such technique is autologous chondrocyte implantation (ACI), which is useful for large, isolated femoral defects in younger patients. In this technique, chondrocytes are extracted arthroscopically from healthy articular surface and grown. The chondrocytes are then injected into the defect that has been covered by a periosteal patch. ACI surgery has reported good to excellent results for reduced swelling, pain and locking in clinical follow ups. However, some physicians have preferred to use undifferentiated pluripotential cells, such as periosteal cells and bone marrow stem cells, as opposed to chondrocytes. These too have demonstrated the ability to regenerate both the cartilage and the underlying subchondral bone.
Another method used to promote normal Articular Cartilage replacement is the technique of transplanting autologous osteochondral plugs. The plugs are taken from a relatively "non-weight-bearing region" of the knee, such as the area just above the intercondylar notch or the edge of the patellar groove, and inserted in the defect. OATS has reported good clinical results with plugs taken from the lateral facet of the patella when treating 10 patients with large femoral OCD lesions. Limitations of this procedure include donor site morbidity, plug damage from percussive forces during insertion, and the technical challenge of placing the plug edges flush with the adjacent articular cartilage.
Fresh osteoarticular allografts have also been used for the treatment of OCD defects. In a study of 126 patients with OCD of the knee, Ghazavi et al reported an 85% success rate at 7.5 years after osteochondral allograft transplantation. This procedure may be an option when other treatments have failed and symptoms persist.
Still, prognosis is favorable in stable lesions (stage I and II) in juveniles with open growth plates; indicating the use of non-operative treatment. However, unstable, large, full thickness lesions (stage III and IV) or lesions of any stage found in skeletally mature patients (closed growth plates) are more likely to fail non-operative treatment and offer a worse prognosis.
The adult form, which occurs in those who have reached skeletal maturity, is most commonly found in patients of ages 16 to 50 years. However, OCD has become more common among adolescent females as they become more active in sports.
The knee is the most commonly involved joint with 75% of cases when compared to the talus, capitellum, and wrist.
The most commonly affected areas of the knee are:
Less frequent locations include:
König named the disease "osteochondritis dissecans", describing it as a subchondral inflammatory process of the knee, resulting in a loose fragment of cartilage from the femoral condyle. In 1922, Kappis described this process in the ankle joint. On review of all literature describing transchondral fractures of the talus, Berndt and Harty developed a classification system for staging of osteochondral lesions of the talus (OLTs). The term osteochondritis dissecans has persisted, and has since been broadened to describe a similar process occurring in many other joints, including the knee, hip, elbow, and metatarsophalangeal joints.
In animals, OCD is considered a developmental and metabolic disorder related to cartilage growth and endochondral ossification. Osteochondritis itself signifies the disturbance of the usual growth process of cartilage, and OCD is the term used when this affects joint cartilage causing a fragment to become loose. OCD in animals is "well recognized but poorly understood".
According to the Columbia Animal Hospital the frequency of affected animals is "Dogs, humans, pigs, horses, cattle, chickens, and turkeys", and in dogs "The most commonly affected breeds include the German Shepherd, Golden and Labrador Retriever, Rottweiler, Great Dane, Bernese Mountain Dog, and Saint Bernard." Although any joint may be affected, those commonly affected by OCD in the dog are: shoulder (often bilaterally), elbow, knee and tarsal (hock).
The problem develops in puppyhood although often subclinically, and there may be pain or stiffness, discomfort on extension, or other compensating characteristics. Diagnosis is via scans such as X-ray, arthroscopy, or MRI, and treatment is often surgical although the best method remains open to debate.
Because an animal may compensate for painful forelegs by misuse of rear legs, there is a possibility that this condition can be masked by other skeletal and joint conditions such as hip dysplasia.