What Is the Treatment of a Subchondral Fracture in the Knee?

A subchondral fracture in the knee affects the bone beneath the cartilage, often causing pain and joint dysfunction. It is frequently seen in older adults with osteoporosis or athletes exposed to repetitive stress. Early diagnosis and treatment are crucial to preventing complications like osteoarthritis or joint collapse.

Treatment depends on factors such as severity, patient activity level, and bone health. Options range from conservative approaches, including rest and bracing, to surgical interventions for severe cases.

Subchondral Anatomy And Knee Stability

The subchondral bone provides structural support beneath the articular cartilage, absorbing mechanical loads and distributing forces to reduce stress on the cartilage. Unlike cortical bone, which offers rigidity, subchondral bone has a trabecular structure that allows for shock absorption. Its vascular network supports nutrient exchange, influencing cartilage health and joint function. A fracture in this region disrupts force distribution, leading to altered biomechanics and increased cartilage degeneration.

Knee stability depends on the integrity of the subchondral bone, ligaments, menisci, and surrounding musculature. The subchondral region ensures smooth articulation between the femur and tibia. A fracture can create an uneven joint surface, leading to abnormal load distribution and accelerated cartilage wear, increasing the risk of osteoarthritis. Bone marrow edema or cyst formation can further weaken the joint’s ability to withstand repetitive stress.

The biomechanical effects of subchondral fractures extend beyond localized bone damage. MRI and CT imaging studies show that these fractures often coincide with cartilage changes and synovial inflammation. A 2021 study in Osteoarthritis and Cartilage found that patients with subchondral insufficiency fractures had higher rates of cartilage thinning over time. Additionally, subchondral bone stiffness affects proprioception, meaning fractures in this region may impair neuromuscular control and increase instability.

Typical Clinical Presentation And Imaging

Patients often experience progressive pain that worsens with weight-bearing activities. Unlike acute fractures, subchondral fractures typically present with an insidious onset of deep, aching pain localized to the medial or lateral compartment. Symptoms may worsen with prolonged standing, stair climbing, or high-impact movements and improve with rest. Swelling may occur due to synovial irritation, though it is usually mild. Some individuals report joint instability or mechanical symptoms like clicking, particularly if there is concurrent chondral damage.

Physical examination findings vary based on severity and chronicity. Tenderness to palpation over the affected compartment is common, especially along the medial femoral condyle, a frequent site of insufficiency fractures. Joint effusion may be present but lacks the warmth or erythema seen in inflammatory conditions. Pain with axial loading, such as during a single-leg stance or deep knee flexion, suggests subchondral involvement. Limited range of motion may occur due to pain inhibition, though significant stiffness is rare unless osteoarthritis has developed. Distinguishing subchondral fractures from meniscal injuries or osteonecrosis is essential due to overlapping symptoms.

Imaging is crucial for diagnosis and assessment. Standard radiographs are often the first step, though early-stage fractures may not be visible. Subtle signs like subchondral sclerosis or joint space narrowing may suggest pathology, but radiographs often underestimate the injury’s extent. MRI is the most sensitive tool, revealing characteristic bone marrow edema patterns. A 2022 study in Skeletal Radiology found that MRI detected early subchondral fractures in 92% of cases where radiographs appeared normal. T2-weighted sequences highlight marrow edema, while T1-weighted images delineate fracture lines and assess cartilage integrity. If MRI is contraindicated, CT scans provide detailed images of cortical disruptions but lack the soft tissue contrast needed for marrow evaluation.

Nonoperative Treatment Methods

Nonoperative management focuses on reducing mechanical stress to allow healing while preserving joint function. Patients are advised to limit weight-bearing on the affected limb. In cases of significant pain, crutches or a walker may be necessary. Unloading braces help redistribute forces, particularly for fractures in weight-bearing regions like the medial femoral condyle. Most patients require at least six to twelve weeks of offloading before gradually resuming normal movement.

Pain management typically involves NSAIDs, though prolonged use may interfere with bone healing. Acetaminophen is often preferred for long-term pain control. In some cases, bisphosphonates or other bone-strengthening agents may be recommended, particularly for patients with osteoporosis. Although their role in subchondral fracture healing is debated, some evidence suggests they help stabilize trabecular bone and prevent collapse.

Biologic therapies, such as platelet-rich plasma (PRP) or bone marrow aspirate concentrate (BMAC) injections, are being explored as potential adjuncts to conservative treatment. These therapies aim to enhance healing by delivering growth factors and stem cells to the injured area. While clinical data is still emerging, early studies suggest they may promote bone remodeling and symptom relief in select patients. Optimizing bone health through adequate calcium and vitamin D intake is also recommended, as deficiencies can impair regeneration.

Surgical Approaches

If nonoperative treatment fails or the fracture leads to structural compromise, surgery may be necessary to restore joint integrity. One option is subchondroplasty, a minimally invasive procedure where a calcium phosphate-based injectable material reinforces the weakened bone. This technique stabilizes the fracture and promotes remodeling, making it useful for early-stage insufficiency fractures without significant cartilage loss.

For fractures causing joint surface irregularities, procedures such as microfracture or autologous chondrocyte implantation may be considered to address cartilage defects. These methods encourage fibrocartilage formation or hyaline-like tissue regeneration, though outcomes vary based on patient age and lesion size. In cases of advanced subchondral collapse or osteoarthritis, high tibial osteotomy can redistribute weight-bearing forces away from the damaged compartment. This realignment procedure is often recommended for younger, active individuals seeking to delay joint replacement.

Rehabilitation Considerations

Rehabilitation is essential for restoring knee function and preventing complications. Early rehabilitation focuses on pain control and swelling management through cryotherapy and compression. Patients undergoing surgery may need a period of limited weight-bearing before progressing, while those treated conservatively can often begin gentle range-of-motion exercises early to maintain flexibility.

As healing advances, rehabilitation shifts to strengthening and neuromuscular re-education. Exercises target the quadriceps, hamstrings, and gluteal muscles to improve knee stability and reduce joint loading. Closed-chain exercises, such as leg presses and step-ups, are preferred to minimize shear forces on the healing bone. Proprioceptive training with balance boards or single-leg drills enhances joint control and reduces reinjury risk.

Return-to-sport protocols are individualized, with high-impact activities reintroduced cautiously based on clinical and imaging assessments. Long-term joint protection strategies, including weight management and activity modification, help prevent recurrent fractures and degenerative changes.