Knee Cartilage Injury
What is the Anatomy and Function of the Knee Cartilage?
The knee joint is lined with two types of tissue that work together to allow smooth, pain-free movement:
Articular (hyaline) cartilage – a smooth, white tissue that covers the ends of the femur (thigh bone), tibia (shin bone), and the underside of the patella (kneecap).
It acts as a low-friction surface, enabling bones to glide smoothly during movement.
Meniscus cartilage – C-shaped fibrocartilage pads that sit between the femur and tibia, acting as shock absorbers and secondary stabilizers.
Articular cartilage has no blood or nerve supply, meaning it does not heal well on its own if injured. Damage to this surface is a common cause of persistent knee pain and degeneration.
How Do Knee Cartilage Injuries Occur?
Cartilage injuries may result from either acute trauma or gradual degeneration over time.
Traumatic cartilage injuries often occur when:
The knee is twisted or pivoted under load (e.g., during sport or sudden change of direction).
There is a direct impact to the joint (e.g., from a fall or tackle).
The cartilage is damaged during a ligament injury, such as an ACL tear.
Degenerative cartilage injuries develop progressively with:
Repetitive stress or overload, especially in high-impact activities.
Malalignment of the leg or prior injury altering joint mechanics.
Aging or early osteoarthritis.
Some younger patients have poor blood supply to the bone underlying the cartilage. This can cause the cartilage to loosen or fragment from the bone. This condition is known as osteochondritis dissecans (OCD).
How Do You Diagnose a Knee Cartilage Injury?
Diagnosis involves a combination of history, clinical exam, and imaging.
Clinical Assessment:
A detailed history of injury or a gradual onset of symptoms.
Localized joint line tenderness or pain with deep knee bending or standing.
Swelling and locking of the knee during range of motion.
Imaging:
MRI scan – the most effective way to detect cartilage defects, assess their size, depth, and location, and evaluate any associated meniscus or ligament injury.
X-rays – used to assess joint alignment and joint degenerative changes.
What are the Long-Term Consequences of Having a Knee Cartilage Injury?
Cartilage has a limited ability to heal, thus, articular surface injuries can lead to progressive joint damage over time. This leads to joint pain, reduced range of motion, and decreased function of the knee.
What are the Indications for Conservative Management of Knee Cartilage Injuries?
Many small or stable cartilage defects can be managed without surgery, especially when symptoms are mild or the joint remains mechanically stable.
Conservative management is appropriate when:
The lesion is small and contained.
The patient has minimal pain or functional limitation.
There is no mechanical locking or catching.
The patient is older or has diffuse degenerative changes.
A stable OCD lesion in a very young patient.
Non-surgical management typically includes:
Activity modification to reduce high-impact loading.
Physiotherapy focusing on strengthening the quadriceps, hamstrings, and hip muscles to improve joint mechanics.
Weight management to decrease load on the knee joint.
Anti-inflammatory medication or injections (e.g., corticosteroid, hyaluronic acid, or PRP) to relieve pain and swelling.
Bracing or taping for unloading or support when indicated.
What are the Indications for Surgical Management of Knee Cartilage Injuries?
Surgical intervention may be necessary when symptoms persist despite conservative treatment or when the defect is large or unstable.
Indications for surgery include:
Large or full-thickness cartilage defects that are symptomatic.
Loose cartilage flaps or fragments within the joint.
Young or active patients with focal cartilage damage but otherwise healthy joints.
Surgical options depend on the size, location, and depth of the defect and may include:
Arthroscopic debridement or chondroplasty – smoothing frayed cartilage to reduce symptoms.
Fixation or removal of a loose OCD fragment.
Microfracture or drilling – stimulating new scar tissue growth in the defect by creating small holes in the bone beneath the defect.
Osteochondral autograft transplant (OATS/mosaicplasty) – transplanting small plugs of healthy cartilage from another part of the knee.
Osteochondral allograft transplant - transplant a medium/large cartilage/bone plug from a cadaveric donor to the patient’s articular defect.
Realignment (osteotomy) – in selected cases to offload the damaged compartment.
The goal of surgical management is to restore a smooth joint surface and reduce pain.
