Osteochondral Injuries of the Knee

Bone and cartilage injuries involve damage to the joint surface or the underlying bone that supports it. Cartilage acts as a shock absorber and friction reducer, but because it lacks a blood supply, it does not heal easily when damaged. When cartilage is torn, softened, or worn away, the exposed bone beneath can become painful and inflamed. Bone injuries can range from deep bruises to small fractures within the joint, often called osteochondral injuries.

In severe cases, a fragment of cartilage and bone can separate completely, a condition known as osteochondritis dissecans. These injuries can result from a single traumatic event or from gradual wear over time, depending on the cause and the patient’s activity level.

Symptoms vary depending on the severity and location of the injury but often include:

• Persistent knee pain, especially during activity
• Swelling or stiffness around the joint
• A sensation of catching, grinding, or locking
• Decreased ability to fully bend or straighten the knee
• Weakness or a feeling of instability like the knee is giving out

Pain from cartilage damage often worsens with weight-bearing activities such as climbing stairs or squatting. If a loose piece of cartilage or bone is floating inside the joint, it may cause locking or a “stuck” sensation.

Bone and cartilage injuries can result from either sudden trauma or repetitive overuse. Common causes include:

• Sports injuries: Sudden twisting, pivoting, or direct impacts during sports such as basketball, soccer, or skiing.
• Knee dislocations: When the kneecap shifts out of place, it can shear off cartilage from the femur or patella.
• Ligament tears: Injuries like ACL or MCL tears can cause associated bone bruises or cartilage damage from abnormal joint motion.
• Repetitive stress: Over time, repeated loading and microtrauma can wear down cartilage, leading to softening and breakdown.
• Degenerative changes: In older adults, cartilage naturally thins and becomes less resilient, increasing the risk of injury from even minor impact.

Several factors increase susceptibility to bone and cartilage injuries:

• High-impact or contact sports that involve jumping, pivoting, or tackling
• Prior knee injuries that alter joint mechanics
• Muscle imbalance or poor alignment placing uneven stress on the joint
• Excess body weight adding strain to the cartilage surface
• Aging, which reduces cartilage elasticity and bone density
• Genetic predisposition to joint degeneration or poor cartilage quality
• Individuals with underlying bone weakness, such as those with osteoporosis or nutritional deficiencies, are more likely to sustain bone bruises or microfractures.

Bone and cartilage injuries to the knee can appear in several forms:

• Bone bruises: Deep injury within the bone tissue causing swelling and tenderness that may last weeks or months.
• Osteochondral fractures: Damage to both bone and cartilage, often from trauma.
• Chondromalacia patellae: Softening of cartilage behind the kneecap, common in runners and athletes.
• Osteochondritis dissecans: A fragment of bone and cartilage separates from the joint surface, sometimes becoming loose within the knee.
• Cartilage defects: Localized areas where cartilage is missing or irregular, often leading to early arthritis if untreated.