Coronary Ligament Strain – The Clinical Syndrome
Strain of the coronary ligaments is an often overlooked cause of medial knee pain and can cause significant pain and functional disability. The coronary ligaments are thin bands of fibrous tissue that anchor the medial meniscus to the tibial plateau. The coronary ligaments are actually extensions of the joint capsule. These ligaments are susceptible to disruption owing to trauma from forced rotation of the knee. The medial portion of the ligament is most commonly damaged.
Patients with coronary ligament syndrome have pain over the medial joint and increased pain on passive external rotation of the knee. Activity, especially involving flexion and external rotation of the knee, makes the pain worse; rest and heat provide some relief. The pain is constant and characterized as aching; it may interfere with sleep. Coexistent bursitis, tendinitis, arthritis, or internal derangement of the knee, in particular of the medial meniscus, may confuse the clinical picture after trauma to the knee joint.
What are the Symptoms of Coronary Ligament Strain
Patients with coronary ligament strain invariably have a history of a rotation injury to the knee. On physical examination, the patient exhibits medial joint tenderness and a marked increase in pain with passive external rotation of the knee. A joint effusion may be present. Subtle knee instability is hard to detect on physical examination because of splinting of the knee as a result of the amount of pain associated with this injury. The neurological examination of a patient with coronary ligament strain is normal. As mentioned previously, coexistent bursitis, tendinitis, arthritis, or internal derangement of the knee, in particular of the medial meniscus, may render a diagnosis on a purely clinical basis difficult.
How is Coronary Ligament Strain diagnosed?
Plain radiographs are indicated in all patients with coronary ligament syndrome pain. Based on the patient’s clinical presentation, additional tests, including complete blood cell count, erythrocyte sedimentation rate, and antinuclear antibody testing, may be indicated. Magnetic resonance imaging (MRI) and ultrasound imaging of the knee is indicated to quantify the extent of internal derangement of the knee and to rule out occult mass or tumor. Bone scan may be useful to identify occult stress fractures involving the joint, especially if significant trauma has occurred. Arthroscopy may ultimately be required as a diagnostic and therapeutic maneuver.
The most common cause of medial knee pain is degenerative arthritis of the knee. Other pathological processes may mimic the pain and functional disability of coronary ligament strain. Lumbar radiculopathy may cause pain and disability similar to that of coronary ligament strain. In such patients, back pain is usually present, and the knee examination should be negative. Entrapment neuropathies of the lower extremity, such as femoral neuropathy, and bursitis of the knee also may confuse the diagnosis; both of these conditions may coexist with coronary ligament strain. Primary and metastatic tumors of the femur and spine also may manifest in a manner analogous to coronary ligament strain.
Initial treatment of the pain and functional disability associated with coronary ligament strain should include a combination of nonsteroidal antiinflammatory drugs (NSAIDs) or cyclooxygenase-2 (COX-2) inhibitors and physical therapy. Local application of heat and cold may be beneficial. For patients who do not respond to these treatment modalities, injection of the coronary ligament with a local anesthetic and steroid may be a reasonable next step.
Complications and Pitfalls
Failure to identify primary or metastatic tumor of the knee or spine that is responsible for the pain may yield disastrous results. The major complication of injection of the coronary ligament is infection. This complication should be exceedingly rare if strict aseptic technique is followed. Approximately 25% of patients report a transient increase in pain after injection of the coronary ligament, and patients should be warned of this possibility.
Coexistent bursitis and tendinitis may contribute to knee pain and may require additional treatment with more localized injection of a local anesthetic and depot steroid. Injection of the coronary ligament is extremely effective in the treatment of pain secondary to coronary ligament strain. This technique is a safe procedure if careful attention is paid to the clinically relevant anatomy in the areas to be injected. The use of physical modalities, including local heat and gentle range-of-motion exercises, should be introduced several days after the patient undergoes this injection technique for knee pain. Vigorous exercises should be avoided because they would exacerbate the patient’s symptoms.