Intra-Articular Causes of Ankle Pain
- Ankle joint effusion.
- Pain or crepitus (or both) with passive ankle joint motion.
Intra-articular pathology is often associated with joint effusion. Ankle joint effusion is best observed over the anterolateral aspect where the soft tissue is thinnest. Severe soft tissue edema and patient body habitus can obscure the physical examination and needs to be differentiated from a true effusion. Pain or crepitus (or both) with passive dorsiflexion and plantarflexion of the ankle are also indicative of an intra-articular process. Occasionally, determining whether the tibiotalar joint or the subtalar joint is the source of the discomfort is difficult. In these cases, a diagnostic injection of a local anesthetic into the ankle joint helps determine the source of pain. Direct palpation of the ankle joint line anteriorly also provokes pain. However, the overlying structures make this method less reliable.
Imaging Studies and Special Tests
The choice of imaging modality depends on the differential diagnosis. Radiographs of the ankle are obtained to evaluate for osteochondral lesions, fractures, loose bodies, and arthritic changes. A standard three-view study includes anteroposterior, lateral, and internal oblique (mortise) views and is preferred. When possible, weight-bearing radiographs should be obtained. MRI is useful for evaluating intra-articular soft tissues such as the synovial lining and joint cartilage and screening for osteochondral defects. When bony detail is required, CT scan is the study of choice.
Obtaining a careful patient history is essential when formulating a meaningful differential diagnosis for ankle joint pain. Key aspects of the patient history to be ascertained include previous trauma (posttraumatic arthritis, osteochondral lesion of the talus, soft tissue impingement, septic arthritis), diabetes or neuropathy (Charcot arthropathy), recent ankle joint injection (septic arthritis, drug allergy), endocarditis (septic arthritis, synovitis), locking or catching of the joint in dorsiflexion or plantarflexion (loose body) and known inflammatory disorders (gout; pseudogout; and reactive, psoriatic, or rheumatoid arthritis). A timely diagnosis of septic arthritis is imperative if the joint is to be preserved. Sometimes infection is difficult to differentiate from an acute, aseptic, inflammatory condition or Charcot. In such cases, joint aspiration is performed to verify the presence of crystals or bacteria, and determine a white blood cell count. Unlike the hip and knee, primary osteoarthritis of the ankle joint is quite uncommon. Most cases result from previous trauma. Charcot arthropathy may present with spontaneous painful or painless swelling and deformity. Pigmented villonodular synovitis is also known to involve the ankle joint.
Ankle arthritis can be quite debilitating for patients. Conservative measures for reducing pain include NSAIDs, avoidance of impact loading activities, and intermittent periods of cast or walking boot immobilization. Glucocorticoid and hyaluronic acid injections can also be considered. A variety of commercially available and custom made braces are available and commonly used for long-term management. Tibiotalar joint arthrodesis remains the “gold standard” surgical treatment option. This procedure is durable and can provide good pain relief but results in an altered gait pattern limiting activity. Total ankle replacement is becoming more popular with the newest generation of prostheses. Indications for the procedure remain narrow and patient selection is critical for success.
Septic arthritis mandates some form of joint irrigation that includes open or arthroscopic approaches or serial joint aspirations in patients considered poor surgical candidates.
Charcot arthropathy of the ankle poses a therapeutic challenge because of the inherent instability associated with the condition. Attempted bracing often leads to ulcer formation over the malleoli creating further treatment difficulties. Therefore, surgical stabilization is an early consideration.
Osteochondral Lesions of the Talus (Osteochondritis Dissecans)
- Ankle joint pain exacerbated by weight-bearing activity.
- No pathognomonic clinical examination findings.
- Advanced imaging (MRI or CT scan) often necessary to make diagnosis.
An osteochondral lesion can be described as a local condition that results in the detachment of a segment of cartilage and its corresponding subchondral bone from an articular surface. They occur most commonly in the knee and third most commonly in the ankle. The term “osteochondritis dissecans” is pervasive in the medical literature and is suggestive of an inflammatory process. However, investigators have not demonstrated the presence of inflammatory cells by histologic sections. Therefore, the term should probably be abandoned. Multiple etiologies have been proposed for osteochondral lesions of the talus (OLTs) including direct trauma, repetitive microtrauma, ischemia, ossification defects, and genetic predisposition.
Most experts agree that trauma is the principle predisposing factor for the development of OLTs, particularly for lateral lesions.
Clinically, OLTs are generally located anterolaterally or posteromedially on the talar dome weight-bearing surface. Central lesions have also been reported. Anterolateral lesions tend to be broad but superficial and wafer-like while posteromedial lesions tend to be deep but involve less articular surface area. A history of trauma is reported in approximately 98% of lateral dome lesions whereas trauma was noted in approximately 70% of medial lesions. The mechanism of their occurrence is often similar to a typical ankle sprain. As a result, acute cases are often misdiagnosed or not detectable at the time of injury on plain radiographs. High-energy injuries resulting from a fall from a height or motor vehicle accident may also create an OLT.
In acute cases, the signs and symptoms are similar to those found in ankle sprains: ecchymosis, ligament pain, ankle swelling, and limited range of motion. Mechanical locking can occur but is not a common complaint. In chronic cases, stiffness, activity-related pain, and intermittent swelling are typical complaints. There are essentially no pathognomonic clinical signs of OLT.
Imaging Studies and Special Tests
A minimum work-up includes anteroposterior, lateral, and internal oblique (mortise view) radiographs of the ankle. The mortise view is usually most helpful. Up to 30–40% of OLT are not visualized on plain radiographs. Either MRI or CT scan is indicated for further work-up. The former is a better screening tool and the latter is often chosen to better characterize a lesion detected on plain radiographs.
Occasionally OLT are discovered as incidental findings on imaging studies. Asymptomatic lesions require no treatment. For symptomatic lesions, treatment depends on the age, size, and stage of the defect. For low-stage lesions, whether acute or chronic, a period of immobilization in a cast or walking boot is recommended along with avoidance of impact loading activities. Acute lesions in younger patients tend to do better with this treatment. For chronic unstable lesions, surgery is usually required to alleviate symptoms. Displaced lesions that result in an ankle joint loose body or lesions that cause mechanical locking to motion of the ankle joint are an absolute indication for surgery.
With the advent of distraction and small joint arthroscopes, the arthroscopic approach to OLT has become the preferred method of treatment. The goals of surgical management of OLT include the debridement of the necrotic sequestrum, addressing cystic lesions, and the reestablishment of a joint surface by fibrocartilage ingrowth, hyaline cartilage replacement, or fixation of a loose fragment. All loose bodies in the joint must be removed. Surgical treatment of OLT should be performed by foot and ankle subspecialty surgeons or surgeons facile with arthroscopic techniques and familiar with OLT treatment algorithms.