Knee Cartilage Defects

Cartilage damage can occur for several reasons:

• Injury or trauma, such as a twisting event, fall, or direct impact
• Sports-related instability, especially with ligament injuries (like ACL tears) that increase shear stress
• Malalignment (bow-legged or knock-kneed alignment) that overloads one compartment
• Meniscus deficiency, since the meniscus helps protect cartilage by distributing load
• Osteochondritis dissecans (OCD), where cartilage and underlying bone are affected together

Sometimes cartilage defects are discovered incidentally on MRI after an injury, even if they are not the primary pain generator.

Symptoms vary based on the size, depth, and location of the defect, as well as whether there is associated swelling or mechanical irritation. Common complaints include:

• Aching pain with activity, especially squatting, stairs, running, or prolonged walking
• Swelling that worsens after activity
• Catching, grinding, or a “rough” feeling with knee motion
• Pain localized to one area of the knee (medial, lateral, or behind the kneecap)

Some patients notice unpredictable flare-ups—good weeks followed by setbacks—particularly if the knee is overloaded.

Diagnosis begins with a careful history and exam to assess swelling, joint-line tenderness, patellofemoral tracking, and alignment. Imaging often includes:

• X-rays: helpful to assess alignment, joint space, and early arthritis
• MRI: the key study for cartilage defects—shows the size, depth, and location of damage and whether bone is involved
• CT scan: occasionally used when bone involvement is significant, or when planning certain procedures

Many cartilage defects are graded based on severity. Clinically, you may hear terms such as:

• Partial-thickness damage (surface fraying/softening)
• Full-thickness damage (down to bone)
• ICRS/Outerbridge grading, which helps describe how advanced the defect is

A cartilage defect rarely exists in isolation from knee mechanics. Two patients can have the same MRI finding, yet very different outcomes depending on:

• Alignment (varus/valgus)
• Meniscus function (intact vs deficient)
• Ligament stability (especially ACL/PLC/MPFL issues)

If abnormal mechanics continue to overload the damaged area, even the best cartilage procedure can fail. That’s why a comprehensive evaluation is essential—sometimes cartilage treatment is paired with procedures that improve biomechanics (for example, osteotomy, meniscus work, or ligament reconstruction).

Many patients begin with nonsurgical treatment, especially if symptoms are mild:

• Physical therapy focused on strength, motion, hip control, and mechanics
• Activity modification and impact management
• Anti-inflammatory medications when appropriate
• In select cases, injections aimed at symptom relief (not cartilage “regrowth”)

If symptoms persist, treatment becomes more individualized and depends on the defect’s size, depth, and location, plus patient age and activity goals. Broadly, options may include:

• Arthroscopic smoothing/chondroplasty (to address unstable flaps)
• Marrow stimulation (microfracture / drilling) for smaller full-thickness defects in selected patients
• Osteochondral grafting (autograft or allograft) when bone involvement is significant or defects are larger
• Cell-based cartilage restoration (such as MACI) for appropriate candidates with focal defects and limited arthritis

Newer technologies are increasingly discussed in joint preservation:

• Aragonite-based biphasic scaffolds (e.g., Agili-C / “CartiHeal”) are designed to address both cartilage and underlying bone in a single-stage procedure for select lesions.
• Focal metallic resurfacing (“focalplasty”) is a joint-preserving resurfacing option for carefully selected patients with isolated defects who are not ideal candidates for biologic restoration and are not ready for partial or total knee replacement.

The “best” option is not one-size-fits-all—it is chosen based on anatomy, imaging, and your goals.