(A) Overview The history of arthroscopic techniques applied to the ankle joint dates back to 1939, when Takagi described the application of arthroscopy to examine the ankle joint. The first article on the use of ankle arthroscopy was published in 1981. Nowadays, arthroscopic techniques are not only used in the ankle joint, but also in the subtalar and interphalangeal joints, but the techniques and instruments still need to be improved. Because of the small size of the foot and ankle joint, the arthroscope used is thinner than the larger joints such as the knee and hip, with a diameter of 1.9, 2.5 or 2.7 mm, which facilitates a more comprehensive and detailed view. The foot and ankle arthroscopy technique also has the advantages of small incision, small trauma, clear display, low complication rate and quick recovery. It can make more accurate judgment on the integrity of articular cartilage, ligament morphology and tension as well as intra-articular synovial structure and deal with them than previous incision surgery. (II) Indications Cartilage or osteochondral injury; osteoarthritis; intra-articular free body; transarticular surface fracture; synovitis; bony impingement and soft tissue impingement syndrome of the ankle joint; early to mid-term talar osteonecrosis; medial and lateral collateral ligament injury or joint instability of the ankle joint; joint infection; arthroscopic-assisted joint fusion; intra-articular tumor; unexplained swelling and pain. (3) Contraindications 1. Absolute contraindications: poor skin condition, local infection or infectious lesions; systemic infectious lesions; systemic condition does not allow the patient to undergo surgery 2. Relative contraindications: joint adhesions or ankylosis; severe narrowing of the joint space; rupture of the collateral ligaments and joint capsule; easy irrigation of the flushing fluid into the skin, causing severe soft tissue swelling (4) Surgical procedure 1. Anesthesia (lumbar anesthesia), supine position, tourniquet on the thigh, inflation, one incision on the medial and one on the lateral side of the anterior ankle joint, first injecting saline into the joint with a syringe until the joint is filled, and then reaching into the arthroscope and instruments from the two incisions to perform the operation. Sometimes the procedure requires additional incisions, such as an anterior internal incision underneath and an anterior external incision underneath, while the posterior joint cavity is handled in a prone position with posterior internal and posterior external incisions. The joint cavity is first explored surgically, there is overall judgment to determine the lesion site, and then therapeutic manipulation is performed with instruments. Soft tissue disease can be removed using a planer. Minor cartilage injuries can be trimmed until the surface is flush and the edges are smooth. Heavy cartilage injuries (cartilage exfoliation and exposure of the subchondral bone surface) require repair, and sometimes incision is required during the repair procedure. In osteoarthritis, the degenerated cartilage is repaired arthroscopically, some of the inflamed synovial membrane is removed, the joint cavity is fully flushed, and the free body, if present, is removed. In soft tissue impingement syndrome of the ankle, the impinging soft tissue, osteochondral or paraphyseal bone is excised or removed arthroscopically with a planer or clamp. For early or mid-stage talar osteonecrosis, arthroscopic drilling to reach the lesion can be used with some effectiveness. In the treatment of transarticular surface fracture, arthroscopy is mainly used to monitor the neatness of the joint surface after repositioning, and internal fixation can be done after the fracture joint disappears and the joint surface is flat, which can reduce the occurrence of arthritis. Joint infection can be treated by arthroscopic cleaning and irrigation. Some benign intra-articular tumors can be removed by arthroscopy and tumor tissue can be taken for pathological examination. Arthroscopy is mainly used to observe the morphology and tension of the ligaments and to treat combined intra-articular injuries in ligament rupture and late post-rupture joint instability. Arthroscopy is used to remove cartilage and to repair the bone surface in cases of advanced joint damage requiring joint fusion. 2. Subtrochanteric arthroscopy The subtrochanteric joint is the joint below the ankle joint and above the heel bone. It can develop the same lesions as the ankle joint. Since the subtalar joint is relatively narrow, in most cases a traction device is applied to hold the joint open for clear and complete visualization. Under anesthesia as above, two to three small incisions are made anteriorly and posteriorly below the lateral fibular tip (the most prominent bony bump on the lateral aspect of the ankle) in a lateral position, and the arthroscope and instruments are extended for manipulation. Cartilage injury can be shaved or trimmed with a scraping spoon or microfracture treatment, diseased synovial membrane shaved and excised, intra-articular ligament injury cleaned up the injury site with a shaver, and those with rupture can be reconstructed arthroscopically (taking the autologous tendon and requiring incision at other sites). 3.Interphalangeal arthroscopy The interphalangeal joint is the joint formed between the toe bones of the toes. Because the interphalangeal joint is very narrow, an arthroscope with a diameter of 1.9 mm must be used to operate it. Two to three small incisions are made on the inside and outside of the dorsum of the toe, and the arthroscope and instruments are inserted for observation and treatment. Treatment is as above. Due to the limited number of procedures that can be performed with a narrow joint arthroscope, simultaneous incisions are often required. With the development of arthroscopic technology, it is possible that even smaller arthroscopes will be invented in the future, making the use of arthroscopy more widespread. (E) Complications Complications of foot and ankle arthroscopy are relatively few, such as neurovascular injury, infection, joint adhesions, etc., and even if they occur, they usually do not cause serious consequences. Therefore, foot and ankle arthroscopy is relatively safe and effective. (vi) Post-arthroscopic rehabilitation Because arthroscopy is less invasive, rehabilitation is significantly faster than incisional surgery. After routine arthroscopic exploration and cleaning, the foot and ankle joint can be fixed with a cotton splint for 2 to 3 days after surgery, and can be partially weight-bearing walked with crutches on the 2nd day after surgery, and the medication can be changed and replaced with an elastic bandage wrap for 3 days, and the foot and ankle joint flexion and extension exercises can be started, and normal weight-bearing walking can be resumed 1 to 2 weeks after surgery, and the flexion and extension exercises can be continued, and muscle strength training can be started, and the mobility can be practiced to normal and sports can be resumed 1 to 1.5 months after surgery. If microfracture, ligament reconstruction, joint fusion and total synovial excision are performed, the rehabilitation time is prolonged and the rehabilitation exercises must be performed under the doctor’s formulation and guidance.