Nearly all articulations of the extremities are synovial or diarthrodial joints. Because they have a joint cavity, they are fairly movable. Anatomic features of the synovial joint are shown in Figure 8-1. The articular cartilage and the articulation are enveloped by a joint capsule and supported by ligaments. The outer stratum of the joint capsule (fibrosum) is made up of dense fibrous tissue. The inner layer (synoviale) consists of loose, highly vascular connective tissue and synovium (synovial membrane).¹ This synovial membrane is usually smooth and glistening and may exhibit infoldings (synovial folds) and slender projections, the larger ones called synovial villae. It is richly supplied with nerves, lymphatics, and blood vessels.

There are two types of membrane or synovial cells, type A and type B. Type B cells are the producers of hyaluronic acid of the synovial fluid.²

The joint cavity contains a viscous fluid, the synovial fluid, produced by the synovial membrane. Analysis of this fluid is helpful in the differential diagnosis of joint swelling because it can distinguish noninflammatory, inflammatory, and septic processes.³

Numerous classifications of synovial disorders can be made. The system presented below incorporates the source of synovial irritation and will be used throughout this chapter:

Patients with complaints of aching, swelling, tenderness, and other signs of joint inflammation should always be carefully evaluated to determine the specific causes of their symptoms. A detailed differential diagnosis must be considered and include the above problems or others as discussed later. A history of trauma or injury is more likely to cause a nonspecific type of synovitis, either localized or generalized; however, trauma can also trigger an underlying specific pathologic process.

Patient evaluation includes a careful history, physical examination, and radiologic testing. Arthritis tests should be used throughout for rheumatoid arthritis, lupus, gout, and other rheumatologic conditions whenever suspicion is present. CT scanning is helpful for three-dimensional imaging of the ankle, especially with bony and soft tissue lesions.⁴ MRI is particularly helpful in demonstrating soft tissue lesions about the foot and ankle: it allows the observer to distinguish blood vessels, nerves, fat, ligaments, tendons, bone marrow, muscles, and fluid clearly, as each has different signal characteristics.⁵ A detailed discussion of radiologic techniques is given in Chapter 2. An algorithm is useful to help evaluate and treat chronic sprain pain patients as seen in Table 8-1.

Plicae, or shelves, have been clearly demonstrated in the knee but are more difficult to find in the ankle. More commonly, congenital bands are seen as an incidental finding when examining the ankle for other types of pathology.

A thorough understanding of the region’s anatomy is necessary. Impingement can occur at the anterior inferior tibiofibular ligament, the lateral gutter, the anterior talofibular ligament, and the anterior tibiotalar ligament (Fig. 8-5A-C). The anterior inferior tibiofibular ligament (AITFL) measures an average length of 23 mm and originates on the distal lateral tibia and then inserts on the anterior aspect of the fibula.²⁷ The anterior talofibular ligament (ATFL) originates on the anterior aspect of the inferior oblique segment of the distal fibula (˜20 mm from the anterior tubercle of the fibula) and then inserts on the body of the talus anterior to the fibular articulating cartilage.²⁸ Additionally, Keller et al. further described the anterior tibiotalar ligament, which originates just anterior to the tibial origin of the AITFL on
the anterolateral tibial plafond with often (58%) having fibers concurrently attached to the anterior fibula between the insertion of the AITFL and origin of the ATFL. The ligament then courses laterally and inferior (˜26 mm) to insert just medial to the insertion of the ATFL²⁷ (Fig. 8-5D and E).

Because the most common mechanism of ankle injury is plantar flexion inversion, chronic lateral ankle pain is much more common than chronic medial pain following a sprain. Typically, the patient complains of vague anterior pain, usually along the anterior and anterolateral aspect of the ankle, sometimes involving the syndesmosis and sinus tarsi regions. Pain is usually absent at rest and present with most activities, limiting the patient’s ability to participate in a given sport. It may be aggravated by ambulation with sensations of weakness and giving way¹⁵ or swelling, popping, or limited ankle motion.²⁰ Often, the patient has seen several physicians and is frustrated by his or her lack of progress.

Physical examination typically reveals significant anterolateral ankle tenderness to palpation with normal or near normal ankle motion. It is not uncommon for patients to also have tenderness along the syndesmosis; anterior gutter, including the anterior talofibular ligament and the calcaneofibular ligament; and many times also the posterior subtalar joint or sinus tarsi. It is important to try to differentiate by selective anesthetic injection lateral gutter pain from subtalar pain, especially in the sinus tarsi. If anterolateral laxity was found, or pain in the subtalar joint was diagnosed, the diagnosis of anterolateral impingement was not made¹⁵ (Fig. 8-6).

Radiologic evaluation is done to evaluate for arthritis, osteochondral lesions, or other pathology as mentioned above, and stress radiographs are done to evaluate for instability.¹⁵ Radiographs may reveal calcification or heterotopic bone in the interosseous space, which indicates previous injury to the distal tibiofibular syndesmosis, with ossicles along the tip of the fibula and the lateral talar dome consistent with injuries of the anterior talofibular ligament. Often, the x-rays are normal, as are a bone scan and CT scan.

CT scan has been found to be helpful at times for diagnosing the cause of chronic ankle pain following a sprain due to its ability to visualize avulsed intra-articular and juxta-articular fragments that were not seen on the plain radiographs.²⁹ Correlation of MRI findings with arthroscopic findings has been variably reported. Previous MRI studies have shown MRI to have a sensitivity of 39% to 42% and a specificity of 50% to 85% in detecting soft tissue impingement of the ankle.³⁰, ³¹ Urguden et al. reported a 50% positive correlation of MRI findings with arthroscopic findings.²⁰ With newer MRI techniques at the Southern California Orthopedic Institute, the sensitivity has increased to 83% and the specificity to 79% for diagnosing soft tissue impingement.³² The impingement lesion is
evaluated on the T1 sagittal MRI film at a slice just medial to the peroneal tendons. The impingement tissue will present as a low-intensity signal anterior to the fibula often extending anterior and into the lateral gutter³² (Fig. 8-7).

Additionally, a “contrast-enhanced, fat-suppressed, three-dimensional (3D), fast-gradient-recalled acquisition in the steady state with radiofrequency-spoiling” MRI sequence has been reported to have a sensitivity of 91.9% and a specificity of 84.4%.³³

At arthroscopy, the medial malleolar-talar articulation and the central portion of the ankle on the anterior gutter are usually normal. Pathology is generally limited to the syndesmosis and the lateral gutter. Patients generally have a synovitis surrounding the anterior inferior tibiofibular ligament, both in front and behind, as well as synovitis of the anterior talofibular ligament.¹⁵, ²⁰ The synovitis is generally firmer with a more elastic consistency.¹⁵ Also noted at surgery is fibrosis of the lateral gutter and chondromalacia of the talus and the fibula in some cases.¹⁵, ²⁰ In addition, a small ossicle or loose body may be hidden in the soft tissues at the tip of the fibula. Occasionally, an adhesive thick scar band, previously described as a meniscoid lesion or inflamed plical band, is present, extending between the anterior and posterior lateral gutter or extending anteriorly (Fig. 8-8).¹⁸, ²⁰, ²², ²⁶ Rarely, a synovial shelf may be present as well spanning across the anterior ankle.²⁰

The patient is placed in a supine position with a non-sterile thigh holder, and the foot is prepared and draped. Usually, a noninvasive distraction strap can be applied (see Chap. 3). Use of the strap allows complete inspection of the entire joint but still permits easy relaxation of distraction to allow surgery in the anterolateral portion of the ankle. All anatomic landmarks are carefully marked out, and the ankle is distended with 10 mL saline from the anteromedial portal. The anteromedial portal is then established and a 2.7-mm short videoscope with a 2.9-mm interchangeable cannula is inserted. The probe is placed through the anterolateral portal, and inflow is through the posterolateral portal.

Initially, visualization with the 30° arthroscope should be done from the anteromedial, anterolateral, and posterolateral portals. The inflow cannula is then left in the posterolateral portal to give a high-flow system. The arthroscope is reinserted in the anteromedial portal, and the anterolateral gutter is debrided with the 2.9-mm full-radius shaver, baskets, and graspers as necessary. Debridement usually includes removing inflamed synovium, thickened adhesive bands, osteophytes, and loose bodies (Fig. 8-9).
All involved tissue is excised down to the underlying cartilage. The synovium, as well as any inflamed capsular or ligamentous tissue, is removed. Care must be taken not to excise the anterior talofibular ligament remnant. Inflammatory tissue may be seen not only in the lateral gutter but also in the syndesmosis in the articular space between the tibia and fibula.

Following the work done while viewing with the 30° arthroscope, the distraction is released one click with the distractor and visualization is performed with the 70° arthroscope. With more distraction applied, anterolateral compartment of the ankle becomes more occluded, thereby making visualization difficult in this region. The best way to visualize the anterolateral gutter is to dorsiflex the ankle (with distraction relaxed) so the entire lateral gutter space opens up. With dorsiflexion of the ankle, the anterior capsule is relaxed and the lateral malleolus moves away from the medial malleolus. At the same time, the fibula is pulled slightly superiorly, while the fibers of the interosseous and tibiofibular ligaments tend to become more horizontal. In addition, the fibula is medially rotated with dorsiflexion (Fig. 8-10). The 70° arthroscope allows increased visualization of the syndesmosis, anterolateral gutter, and talus and allows better visualization along the posterior gutter from the anterior portals (Fig. 8-11).

With biopsy of the impingement lesions studied at the Southern California Orthopedic Institute, moderate synovial hyperplasia with subsynovial capillary proliferation was observed in all specimens with many displaying fibrosis and hyaline cartilage degeneration (Fig. 8-12). These findings were representative of a chronic inflammatory process.¹⁵ Further studies have supported the findings of meniscoid lesions having a hyalinized and fibrous stroma.²⁶

In general, ligamentous tissue was not seen on histologic analysis.