Obsessing about Osteochondritis Dissecans

Osteochondritis dissecans (OCD) of the knee is a pathological entity initially presenting as vague internal knee pain. Chris Mallac takes a deep dive into OCD and uncovers the clinical presentation and management.

Introduction

Osteochondritis Dissecans (OCD) primarily occurs when the subchondral bone undergoes blood flow disruption leading to ischemia and damage. It may present as insidious, poorly localized internal knee pain with varying degrees of stiffness. Knee joint swelling, locking, and giving way should alert clinicians to an intra-articular pathology.

Causes

1. Traumatic

Repetitive microtrauma may lead to bone ischeamia⁽¹⁾. The femoral condyle is at high-risk for microtrauma as the inferomedial patella or the medial tibial spine makes contact with the lateral aspect of the medial femoral condyle^(1,2).

2. Ischaemic

High-risk OCD sites may have altered vascular architecture. Combined with repetitive trauma, this may activate an ischaemic event and progression to OCD^(2,3).

3. Hereditary

The presence of OCD in identical twins suggests there may be a genetic predisposition⁽⁴⁾. An endoplasmic reticulum storage disease phenotype leads to an alteration in chondrocyte matrix synthesis and may provide physiological reasoning to the hereditary cause⁽⁵⁾.

Incidence

In the general population, the incidence of OCD is 15-29/100 000⁽⁶⁾. Active, skeletally immature males between the ages of 13-21 are at the highest risk for developing OCD through microtrauma^(1,7). The active epiphysis in the growth spurt stage is a primary risk factor. The ratio between males and females is 5:3⁽⁷⁾.

The medial femoral condyle is the most prevalent area, with the lateral aspect representing 39% of OCD cases. The lateral femoral condyle presents 17% of cases, with a concomitant discoid meniscus present in many instances. The patella, trochlear groove, and tibial plateau are the least prevalent sites of OCD⁽⁸⁾.

Classification

Osteochondritis dissecans progresses along four successive stages (see figure 1). The stages are defined radiologically with X-ray and magnetic resonance imaging (MRI) or direct visualization upon arthroscopy (see table 1)^(9,10,11).

Figure 1: stages of OCD

1. Stage 1Subtle changes in the subchondral bone with intraosseous subchondral osteopenia⁽¹²⁾.

2. Stage 2

Intraosseous edema of the subchondral bone due to microfracture of the trabecular bone structure⁽¹³⁾.

3. Stage 3

A sclerotic ring demarcates the healthy bone from the lesion. Osteonecrosis of the bone is found in the centre of this ring and the cartilage structure appears intact on imaging⁽¹²⁾.

4. Stage 4

As the bone undergoes further necrosis around the rim,  a fragment loosens and may detach in multiple pieces⁽¹²⁾.

	Xray	MRI	Arthroscopy
Stage 1	A small area of subchondral bone compression	Thickening of articular cartilage with no break	Softening and irregularity of the cartilage. There is no fragment present
Stage 2	Partially detached fragment	Breached articular cartilage with low signal rim behind the fragment indicating attachment	Breached articular cartilage, with a fragment that cannot be displaced
Stage 3	Fully detached fragment still in the underlying crater	Breached articular cartilage with high signal T2 changes behind the fragment suggesting fluid	Defined fragment - flap lesion fragment that is partially displaceable
Stage 4	Complete detachment or loose body	Defect of the articular surface with a loose body	Loose body and defect in articular cartilage

Management                                        

The primary aim of OCD management is the protection of articular cartilage and promotion of subchondral bone healing⁽²⁾. Several factors affect the prognosis of conservative treatment⁽¹⁴⁾. First, early and stable lesions have a better prognosis than late, unstable lesions. Second, lesions smaller than 1.3mm have a better prognosis⁽¹⁵⁾. Third, lateral femoral condyle lesions have a better prognosis than medial femoral and patella lesions. Fourth, the presence of a discoid meniscus has a poorer prognosis due to the oversized meniscus causing excessive stress at the articular surface during motion⁽¹⁶⁾. Finally, juvenile OCD has a better prognosis due to an open and active physis.

Stable vs. unstable lesions (2)

Stable lesions should be treated non-operatively. Conservative management includes restricting repetitive compressive and shear force activities such as running, jumping, squatting, and cutting sports. Depending on the degree of injury, weight-bearing is limited to either NWB or PWB. Following the initial period of activity restriction, a progressive strengthening program is a cornerstone of successful management. In addition, clinicians may utilize adjunctive therapies such as electrotherapy modalities throughout the rehabilitation process⁽¹⁴⁾.

An MRI is conducted 12 weeks into the conservative period to review healing. Athletes may begin a four-week progressive weight-bearing and rehabilitation program following improved symptoms and signs of radiological healing. If symptoms have not subsided, but the MRI shows healing, clinicians may restrict impact activities for a further 12 weeks. Clinicians should consider surgery if there is no improvement in symptoms or radiological healing at three months⁽²⁾.

Surgical management prefers to reattach the existing articular cartilage fragments as the potential for healing is possible (see table 2)⁽²⁾. Removing the OCD fragment without arthroplasty techniques will increase the chance of the patient developing knee OA by 38%⁽¹⁷⁾.

Unstable fragment	Surgical technique
Undisplaced and attached	Fixation with absorbable pin fixation
Undisplaced and attached with cyst	Bone graft of cyst and fixation with metal screws
Displaced	Fixation with absorbable pins for young patients and metal screws for older patients, with fragment trimming
Excessively fragmented	Excision with restorative treatment such as microfracture procedures and osteotomy, or

Post-Surgical Rehabilitation 

There are four phases of post-surgical OCD rehabilitation (see table 3); however, the degree of injury guides the rehabilitation process. Therefore, adherence to site-specific precautions is vital to ensure the protection of articular cartilage and subchondral bone. Clinicians should be cautious with weight-bearing sites (e.g., tibiofemoral lesions) and higher degrees of injury as the compressive forces may impact the recovery. Athletes with tibiofemoral lesions should remain NWB for six weeks post-surgery, followed by six weeks of PWB. Clinicians should restrict resisted exercises for 12 weeks. Athletes may commence unresisted stationary cycling and continuous passive motion (CPM) within the first 12 weeks to improve their range of motion (ROM). The surgeon should guide the flexion range to limit the contact between the tibia and lesion. Running and return to sports should be delayed to six and nine months, respectively⁽²⁾.

The patellofemoral joint is non-weight-bearing. Therefore, athletes may commence weight-bearing with the knee locked in a full extension brace for the first 6-8 weeks. In addition, to prevent joint stiffness, clinicians may utilize CPM for the first six weeks⁽²⁾.

Phase		Goal	Exercises
Protection	8 weeks	Tissue healing and restoration of quadriceps function	Non-weight bearing exercises such as heel slides, inner range quadriceps, straight leg raises, and prone leg curls
Movement restoration	9-12 weeks	Progress to full weight-bearing and normalized gait, full range of motion, and initiation of closed kinetic chain exercises	Gait re-education drills, bilateral balance work, air squats in a limited range of motion (surgeon dependant), lumbopelvic strength, unresisted stationary bike
Strength	13-18 weeks	Progressive strengthening and return to running	Progressive unilateral weighted quadriceps and gluteal strength, single leg balance, landing mechanics, and introductory agility drills
Return to training and competition	19+ weeks	Return to training and competition.	The introduction and progression of sport-specific change of direction and agility drills.

Conclusion

The current global pandemic has meant that previously active individuals have spent prolonged periods in lockdown with limited high-impact physical activity. As athletes return to sport, the incidence of load-related injuries is likely to increase. Although the prevalence of OCD is relatively rare, a presentation of insidious, vague knee pain with mechanical symptoms such as locking and giving way should alert clinicians to the presence of intra-articular pathology. A thorough clinical examination and appropriate radiological investigation may be needed to confirm an OCD diagnosis. Young athletes do well with conservative treatment; however, surgical fixation may be necessary for mature athletes. The preservation of articular cartilage should remain the primary goal for any management strategy.

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