What is the recommended evaluation and management for chronic osteochondral knee fragmentation in a 30‑70‑year‑old adult with persistent knee pain, occasional mechanical symptoms, and no significant comorbidities?

Chronic Osteochondral Knee Fragmentation: Evaluation and Management

Initial Diagnostic Approach

Begin with standard three-view knee radiographs (anteroposterior, lateral, and patellar views) to confirm the presence of osteochondral fragments, assess lesion size, and exclude other pathology. 1

Key Radiographic Findings to Document

• Fragment size and location – Lesions >2 cm² carry worse prognosis and greater risk of degenerative changes 2
• Presence of loose bodies – Indicates complete fragment detachment requiring surgical consideration 1
• Joint space narrowing – Suggests progression to osteoarthritis 2
• Subchondral bone integrity – Determines fixation versus excision approach 3

Advanced Imaging: MRI Without IV Contrast

MRI without contrast is the appropriate next study when radiographs demonstrate osteochondral defects, loose bodies, or history of cartilage injury. 1, 4

Critical MRI Assessment Points

• Cartilage integrity and extent of defect – Defines surgical candidacy 1
• Subchondral bone marrow edema – May indicate subchondral insufficiency fracture rather than classic osteochondritis dissecans 5
• Meniscal pathology – Frequently coexists and influences treatment planning 4, 5
• Ligament integrity – Particularly medial patellofemoral ligament if patellar fragmentation present 1
• Loose body identification – MRI detects loose bodies with high accuracy 1, 4

When to Consider CT

• CT without contrast may be appropriate if surgical planning requires detailed visualization of fragment geometry or patellofemoral anatomy in cases of recurrent subluxation 1
• CT arthrography offers 86-100% sensitivity for loose bodies and cartilage evaluation when MRI is contraindicated 1
• Do not order CT if MRI is already normal – it provides no additional diagnostic value 6

Exclude Referred Pain Sources

Before attributing symptoms solely to knee pathology, evaluate the hip and lumbar spine clinically. 4

• Obtain hip radiographs if groin pain, restricted hip range of motion, or unexplained persistent knee pain despite normal knee imaging 4
• Obtain lumbar spine radiographs if low-back pain, radicular symptoms, or posterior thigh pain present 4

Surgical Decision Algorithm

Fragment Fixation (Preferred When Feasible)

If adequate subchondral bone is attached to the fragment and the patient is skeletally mature, drilling with fixation using autologous cortical bone pegs or screws is the preferred approach. 3, 7

• Indications for fixation: Unstable or loose fragments with sufficient bone stock for stable fixation 3, 7
• Outcomes: Excellent or good results in 75% of patients at 5-year follow-up 7
• Augmentation: Autologous bone graft may be necessary to reconstruct subchondral contour 3

Fragment Excision with Microfracture

For fragments without adequate bone for fixation, or failed prior fixation, arthroscopic excision of the fragment with microfracture of the crater is the appropriate treatment. 2, 8, 3

Indications

• Grade III or IV osteochondritis dissecans lesions (partial or complete fragment detachment) 2
• Unstable osteochondral lesions with mechanical symptoms (locking, clicking) 8
• Lesion size <2 cm² – Better outcomes with smaller defects 2, 8
• Focal, contained lesions <4 cm² with minimal osteoarthritis 1

Expected Outcomes

• 85% excellent or good results at 9-year follow-up for excision with debridement 2
• Favorable pain relief and return to activities with microfracture technique 8
• Radiographic degenerative changes: 45% show Fairbank changes without joint space narrowing; only 5% progress to significant joint space narrowing 2
• Larger lesions (>2 cm²) correlate with greater degenerative changes 2

Postoperative Protocol

• Non-weight bearing for 6 weeks 8
• Immediate quadriceps strengthening and range-of-motion exercises 8
• Progressive weight bearing after 6 weeks 8

Advanced Cartilage Restoration (For Failed Microfracture or Large Defects)

If microfracture fails or the lesion is too large (>4 cm²), consider mosaicplasty, osteochondral allograft transplantation, or autologous chondrocyte implantation. 1, 3

• Mosaicplasty and osteochondral allograft produce hyaline or hyaline-like cartilage superior to fibrocartilage from microfracture 3
• These techniques are particularly applicable in younger patients (age ≤50 years) to delay or prevent total knee arthroplasty 1

Common Pitfalls to Avoid

• Do not attribute mechanical symptoms to "normal joint sounds" when effusion and chronic pain coexist – this combination mandates MRI 4
• Do not delay MRI in chronic pain with mechanical symptoms – repairable meniscal tears may progress to irreparable degenerative tears 4
• Do not perform knee aspiration for small chronic effusion unless infection or crystal arthritis is suspected 1, 4
• Recognize that larger lesions (>2 cm²) have significantly worse outcomes – counsel patients accordingly and consider earlier advanced reconstruction 2
• Do not assume all subchondral lesions are osteochondritis dissecans – subchondral insufficiency fracture, avascular necrosis, and osteoarthritis present similarly on imaging 5

Conservative Management (Interim or Non-Surgical Candidates)

• Activity modification: Avoid deep squatting, pivoting, and movements provoking symptoms 4
• NSAIDs: Provide symptomatic relief when not contraindicated 4
• Physical therapy: Quadriceps strengthening and range-of-motion exercises 4, 8
• Non-weight bearing or protected weight bearing may be appropriate for acute-on-chronic symptoms 8