Osteochondritis dessicans

Osteochondritis Dissecans (OCD) is osteonecrosis of subchondral bone, with secondary damage to overlying articular cartilage. It is characterized by degrees of osseous resorption, collapse, and fragmentation.¹ There are juvenile and adult forms of this condition; the juvenile form occurs in children or adolescents with open growth plates (skeletally immature). Since the vast majority of OCD occurs in the knee, the article herein is focused on OCD of the knee.

The exact pathophysiology is unknown; however, a disruption of blood supply to subchondral bone is thought to be the underlying mechanism for OCD. Proposed causes include localized avascular necrosis, chronic microtrauma or acute trauma, joint malalignment, and genetic predisposition, among other causes.^1-3 Other considerations include systemic vasculopathies, inflammation, endocrine or metabolic factors, and degenerative joint disease.^1-3

OCD affects adolescents at a rate between 15 to 30 per 100,000.⁴ It is more common in males than in females.³ The highest incidence of juvenile OCD is among patients 10 to 15 years old.⁵ OCDs are significantly more common in the knee (75% or more of cases), followed by the elbow (6% of cases) and ankle (4% of cases).¹ The most common location for juvenile OCD of the knee is the lateral portion of the medial femoral condyle.¹

Risk factors for developing OCD are unclear. It has been suggested that having a familial predisposition may be a risk factor; however, research has uncovered mixed findings. Genetics may play a role. Additionally, malalignment has been found to be a risk factor for OCD. Those with varus knee were more likely to have medial knee lesions.³ Discoid menisci have been shown to be a risk factor in the lateral knee.¹

In 1888, Konig first described OCD and at the time suggested inflammation as the cause of these lesions.¹ Additional research has suggested, however, that the cause may be multifactorial in nature and is most likely due to repetitive microtrauma and compromised vascular supply, evidenced by a higher association between sports participation and OCD. Another explanation is involvement of the endochondral epiphyseal growth plate, which can be injured either acutely or repetitively over time. With skeletal growth, the uninjured region of the endochondral epiphyseal growth plate continues to ossify, whereas the injured region, either temporarily or permanently, ceases ossification, leading to development of OCD.

Disease stages are described on plain radiographs as follows:

Stage 1: small fragment of compression/flattening of subchondral bone, nondisplaced.
Stage 2: partially detached fragment.
Stage 3: completely detached fragment that remains within the underlying crater bed, nondisplaced.
Stage 4: completely detached and displaced fragment, known as a loose body.

Disease stages are described on MRI as follows:

Stage 1: articular cartilage thickening and low signal changes
Stage 2: Breached articular cartilage, low signal rim behind the fragment (fibrous detachment)
Stage 3: Breached articular cartilage, high signal change behind the fragment (synovial fluid)
Stage 4: Loose foreign body

Disease stages are described arthroscopically as follows:

Stage 1: Irregular, softened articular cartilage with no fragment
Stage 2: Breached articular cartilage, with non-displaced, definable fragment.
Stage 3: Breached articular cartilage, with displaced, but attached by overlying cartilage, definable fragment.
Stage 4: Loose foreign body

Lesions at Stage 1 are rarely detected, possibly due to its brief duration of months after the onset of symptoms.⁶ The lesion may fail to heal over time, but the joint itself can be asymptomatic if allowed to heal with activity modification and rest.⁷

With the loss of bone and cartilage based on the severity of OCD, there may be an increased risk for developing osteoarthritis (OA) later in life.

History should include a standard assessment of pain (location, intensity, characteristics, quality, duration, mechanism of onset, exacerbating and relieving factors, and associated symptoms). Activity-related pain should be assessed and it should be determined if there was a specific traumatic event at the onset of pain. The duration of pain can be ongoing and mild for several months before patient presentation to a provider. Additionally, history of mechanical symptoms, such as locking, catching, popping, or buckling, should be taken.

Examination should include gait, inspection (including overall alignment), palpation, and range of motion of the injured joint. The child may have a mildly antalgic gait or avoidance of the injured side. Mobility and activities of daily living otherwise should be normal. Additionally, an effusion may be present on exam. There may be loss of range of motion or pain at the end range. There may be pain over the peri-articular regions. Varus or valgus malalignment should be assessed with a goniometer at the knee and considered because this can increase the risk of developing OCD.

The Wilson sign is a provocative examination maneuver that may indicate a knee OCD lesion, specifically of the medial femoral condyle, the classic location for the lesion. With the patient sitting and knee flexed, the affected knee is actively extended with rotation of the tibia medially. At around 30 degrees of flexion, pain is elicited. At that point, the tibia is rotated laterally, which should then relieve the pain. The sensitivity of this test, however, may be as low as 25%.

Pain can be assessed using a numerical rating scale. Another assessment tool that may be helpful to help ascertain functional limitations and track improvement over time is the Pediatric/Adolescent Outcomes Data Collection Instrument.⁸ This scale is designed to assess young patients and ask questions about overall health, pain, and ability to participate in normal daily activities, and in more vigorous activities associated with young people. This scale is used regularly in research to collect uniform data on outcome measures.

There are no laboratory findings associated with OCD.

OCD can be diagnosed on plain radiographs, able to determine the size and location of the lesion. Magnetic resonance imaging (MRI), however, is the preferred advanced imaging modality for the assessment of OCD, able better to assess the subchondral bone and the surrounding cartilage and other soft tissue structures. MRI is also often ordered when patients continue to experience symptoms, despite negative plain films and conservative measures.

The stability of the OCD lesion influences treatment plan and therefore should be described. Imaging findings for lesion instability for both adults and juveniles on MRI are characterized as follows: (1) high signal surrounding the lesion, (2) focal defect in the articular cartilage, (3) fracture of the articular cartilage, and (4) presence of subchondral cysts. However, most lesions with a high T2 signal in the base healed in younger, skeletally immature patients.

For juvenile OCD, having all 4 of these criteria was noted to have 100% sensitivity for instability. With the addition of the following secondary criteria, the specificity was also 100%: (1) multiple breaks in the subchondral bone plate, (2) outer rim of the T2 signal intensity, and (3) rim of fluid signal intensity.

Those with stable lesions are predicted to heal more quickly and with less aggressive measures than those with unstable lesions. In addition, skeletally immature patients have been found to have better outcomes, compared to skeletally-mature, or adult, patients. Progression to surgery does not differ between genders. There are no data to suggest that the size of the lesion or pain with presentation influences overall outcome. With a loss of bone and cartilage based on the severity of OCD, there could be an increased risk for developing OA later in life.

Special consideration of the child’s school and non-weightbearing status should be explored. Additionally, the child’s home environment should be assessed, including the need to climb stairs/hills to reach home.

Social history should be obtained from the patient in regards to sports played, level of competition, and hours of activity per week to help when considering return to play.

The American Academy of Orthopedic Surgeons (AAOS) published in 2010 clinical practice guidelines on the diagnosis and treatment of OCD of the knee, based on systematic review of published studies. The summary of recommendations is as follows:

• In a patient with knee symptoms and/or knee signs on examination, x-rays are an option.
• No recommendation for or against x-rays of the contralateral, asymptomatic knee in patients with confirmed OCD of one knee.
• In patients with known OCD knee lesions on x-ray, an MRI of the knee is optional to characterize the lesion or when concomitant knee pathology is suspected.
• No recommendation for or against non-operative treatment for asymptomatic skeletally immature patients with OCD.
• No recommendation for or against a specific non-operative treatment for symptomatic skeletally immature patients with OCD.
• No recommendation for or against arthroscopic drilling in symptomatic skeletally immature patients with a stable lesion who have failed to heal with non-operative treatment for at least three months.
• It is the opinion of the work group that symptomatic skeletally immature patients with salvageable unstable or displaced OCD lesions be offered the option of surgery.
• No recommendation for or against a specific cartilage repair technique in symptomatic skeletally immature patients with unsalvageable fragment.
• No recommendation for or against repeat MRI for asymptomatic skeletally mature patients.
• No recommendation for or against treating asymptomatic skeletally mature patients with OCD progression (on imaging) like symptomatic patients.
• It is the opinion of the work group that symptomatic skeletally mature patients with salvageable unstable or displaced OCD lesions be offered the option of surgery.
• No recommendation for or against a specific cartilage repair technique in symptomatic skeletally mature patients with unsalvageable OCD lesions.
• It is the opinion of the work group that patients who remain symptomatic after OCD treatment have a history and physical examination, x-rays, and/or MRI to assess healing.
• No recommendation for or against physical therapy for patients with OCD treated non-operatively.
• It is the opinion of the work group that patients who have received surgical treatment of OCD be offered post-operative physical therapy.
• No recommendation for or against counseling patients about whether activity modification and weight control prevents onset and progression of OCD to osteoarthritis (OA).

The AAOS subsequently published in 2015 Appropriate Use Criteria (AUC) for the treatment of OCD, based on the AAOS Clinical Practice Guidelines described above. 12 treatment options were evaluated for 64 possible OCD clinical scenarios, with recommendations on the appropriateness of each treatment option for each clinical scenario rated as “Appropriate,” “May Be Appropriate,” or “Rarely Appropriate.” The following treatments were addressed in the AUC:

• Activity Restriction – Eliminate impact or painful activities
• Physical Therapy
• Nonoperative management – casting
• Nonoperative management – bracing
• Nonoperative management – restricted weight-bearing (assistive devices)
• Drilling of intact OCD lesion (retro-articular or trans-articular)
• Fixation with or without bone grafting
• Fragment excision and isolated debridement
• Fragment excision and marrow stimulation
• Osteochondral autograft transfer
• Osteochondral allograft transplantation
• Autologous chondrocyte implantation (with or without bone grafting)

The AAOS has a convenient, online web-based application (and phone app) where the practitioner enters select patient data, and the application outputs the appropriate OCD treatments recommended from the above list. The online application may be found at http://www.orthoguidelines.org/auc website.

There are no published clinical guidelines for rehabilitation; however, the most rigorous study to date regarding non-operative treatment of stable OCD of the knee consisted of the following⁹:

• Six weeks of casting to limit weightbearing/mobility.
• Every 4 to 6 weeks, radiographs should be repeated in order to look for re-ossification/healing. If none is seen, the child would be allowed to rest from casting with non-weightbearing joint mobilization, and then recasting for up to 12 weeks total in a cast.
• Once re-ossification is noted on radiographs or 12 weeks has elapsed with casting, the child is given an unloader brace with impact restrictions (no running, jumping, sports), with repeat radiographs every 6 to 8 weeks.
• At each interval, if radiographs show continued healing, the child is progressed to increased activity for 6 months, or until pain-free. Once there is total re-ossification of the lesion, the child is allowed to proceed with unrestricted activity, without bracing.

Most studies suggest that, for juvenile OCD and stable lesions, the outcome for full healing is excellent with non-operative treatment and should be first line.

• Initially, when a patient presents with acute pain, the treatment should be based on limiting weight bearing, reducing inflammation and swelling, and controlling pain.
• After diagnosis of OCD, the lesion should be categorized utilizing MRI as either stable or unstable. If the lesion is stable and pain is improved with limits on weight bearing (with activity modification, bracing, or casting), the patient can start the rehabilitative phase.
  • Additionally, there may be a role for electrical or ultrasound bone stimulators to help with pain.¹⁰
  • Physical therapy can be utilized to correct any malalignment/strength deficits after restricted weight bearing with strengthening and stretching around the joint and improving abnormal movement patterns.

Successful outcomes have been reported to occur with non-operative treatment in 50% to 94% of cases³ and should be trialed for a period of 3 to 6 months before considering surgical options. Larger (>288 mm²) lesions have been shown to have a higher failure rate of re-ossification with non-operative treatment in the knee.⁹ For stable lesions, arthroscopic drilling from a transarticular antegrade or extra-articular retrograde approach is an option. For unstable lesions, surgical options include arthroscopic reduction and internal fixation with screws, microfracture, bone grafting, and fixation with autograft osteochondral plugs.¹

Coordination of care between the physiatrist and an orthopedic surgeon can be helpful if non-operative treatment is not successful in reducing pain complaints and/or function. Additionally, care should be coordinated with a physical therapist that can help to initiate strengthening/stretching around the immobilized joint as the child begins to weight-bear and improve abnormal movement patterns and baseline malalignment.

Joints of patients having unstable OCD lesions, despite surgical treatment, have been observed over time, often to progress to early osteoarthritis. A number of recent interventions have shown promise in reducing risk of progressive joint degeneration for patients with unstable OCD lesions that have failed surgical fixation or have had the unstable fragment removed. One such intervention is a regenerative intra-articular injection technique utilizing mesenchymal stem cells (MSCs), derived from sources such as adipose tissue or bone marrow, among other sources. MSCs have the ability to differentiate into chondrocytes and osteoblasts, as well as to promote tissue repair through growth factor and cytokine expression. These potentially chondrogenic MSCs have been shown in various studies of osteochondral defects to develop into hyaline-like cartilage and collagen.

Another emerging treatment option for OCD lesions is extracorporeal shock wave therapy (ESWT), utilizing high amplitude, abrupt pulses of mechanical energy applied locally to the affected area.. This unique intervention has been employed for the management of early stage OCD in adult patients, to help prevent progression to early osteoarthritis of the affected joint. ESWT has been shown in various studies to have a chondroprotective effect and to improve cartilage and subchondral bone healing.

For children with insidious, chronic joint-related pain, without an acute traumatic event, OCD should be considered as a possible cause of symptoms. Additionally, if an acute traumatic event did occur, OCD may also be seen. Imaging should be considered with any evidence of intra-articular injury (effusion, locking, etc.) or ongoing chronic pain, to decrease time to diagnosis and eventual treatment.

Other pediatric injuries of the knee include tibial tubercle and patellar apophysitis (Osgood-Schlatter or Sinding-Larsen-Johansson, respectively), which can cause pain symptoms that are extra-articular. They do not cause any intra-articular symptoms, such as effusion or locking, which helps to differentiate them from OCD.

There are surgical treatments that have been attempted in the treatment of unstable lesions; however, their role in OCD is unknown. These restorative techniques include microfracture, osteoarticular transfer system, or autologous chondrocyte implantation. Salvage procedures, such as osteochondral allografts, should not be attempted as a first line procedure, but may be helpful in larger and deeper OCD lesions.

In the treatment of OCD, there are still several gaps in knowledge. The etiology of acquiring OCD is unknown. Additionally, although MRI is a helpful tool in staging the injury and determining stability, there are no known imaging findings that correlate with prognosis or length to recovery. Finally, the natural history and progression for OCD lesions is still unclear. Most recommend non-operative treatment in skeletally immature patients for the first 3 to 6 months in stable lesions. However, the type of non-operative treatment and length of time for healing is less clear.