Hip and Knee Pain

6/11/2019 Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 8e Chapter 281: Hip and Knee Pain Kelly P. O'Keefe; Tracy G. Sanson INTRODUCTION AND EPIDEMIOLOGY Every practicing emergency physician over his or her career will see hundreds of patients with complaints of hip or knee pain that are unrelated to major trauma or an acute fracture. Discomfort and limitations to normal use in these areas are typically related to the minor trauma that occurs on a repetitive basis from performing routine daily functions or exercising. Athletes of all varieties are especially prone to these maladies, where strenuous activity transmits forces that are equivalent to three to five times the body weight directly to these major joints. Conversely, the problem of obesity similarly contributes to joint and supporting structural stress and pain.1 However, be alert to the various catastrophic processes that can mimic more mundane etiologies, including ruptured abdominal aortic aneurysm, epidural abscess, and septic joint (among others). Pay close attention to historical points, specific risk factors, abnormal vital signs, and physical findings to avoid making a life- or limb-threatening misdiagnosis. PATHOPHYSIOLOGY AND ANATOMY The hip is a ball-and-socket joint (enarthrosis), allowing motion in all directions. The hip is similar to the shoulder in this capacity, but is much more sTable and relatively resistant to dislocation. The bones of the joint (femoral head, pelvic acetabulum) are strongly reinforced with a fibrocartilaginous labrum, a joint capsule, overlying ligaments, and numerous muscles. The knee is the largest synovial joint in the body and is relatively complicated in structure, comprising two distinct articulating groups: the tibiofemoral and patellofemoral joints. The patella floats above the main joint, attaching to the femur superiorly by the quadriceps tendon and inserting into the tibia inferiorly by the patellar ligament. The knee is stabilized internally by the anterior and posterior cruciate ligaments, and externally by the medial and lateral collateral ligaments. In addition, distal to the main joint, the fibular head attaches by ligaments to the proximal lateral tibia. The medial and lateral menisci are interposed between, and protect, the femoral and tibial condyles. Numerous muscles, tendons, bursa, and additional ligaments add to the complexity of the joint and serve as potential sources for pain and dysfunction (Figures 281-1 and 281-2). FIGURE 281-1. Anterior view of the knee. [Reproduced with permission from Simon RR, Sherman SC, Koenigsknecht SJ: Emergency Orthopedics: The Extremities, 5th ed. © 2007, McGraw-Hill Inc., New York.] 1/31 6/11/2019 FIGURE 281-2. Medial view of the knee. [Reproduced with permission from Simon RR, Sherman SC, Koenigsknecht SJ: Emergency Orthopedics: The Extremities, 5th ed. © 2007, McGraw-Hill Inc., New York.] NERVES OF THE UPPER LEG AND REFERRED PAIN The femoral and sciatic nerves are the major nerves within the thigh (Figure 281-3). The femoral nerve is the largest branch of the lumbar plexus, and the sciatic is the longest nerve in the body, traveling posteriorly and supplying sensation to the hip joint through its articular branches. The femoral and obturator nerves also innervate the hip. The femoral nerve divides into anterior and posterior branches, with the posterior becoming the saphenous nerve and providing sensation to the lower leg. The anterior nerve supplies sensation to the anterior medial thigh by the medial and intermediate cutaneous nerves. The 2/31 6/11/2019 two major branches of the sciatic, the peroneal and tibial nerves, course through the posterior fossa of the knee, along with the popliteal artery and vein. FIGURE 281-3. Nerves that innervate the thigh. Pain in the area of the knee is not commonly referred to other sites, and knee pain is usually due to local pathology. However, referred pain from hip pathology is commonly felt in the buttocks, thigh, or groin; may extend to the knee; and may even travel to the foot. Pain felt in the hip and surrounding locations may be referred from pressure on the proximal nerve roots as they exit the lumbar and sacral spine. In the patient with appropriate risk factors, consider expansion or rupture of an abdominal aortic aneurysm as the cause of hip pain that is not otherwise explained by the history or physical examination, especially when there are no preexisting joint issues. Bedside US may exclude this life-threatening diagnosis. Other extra- articular sources of hip pain include intra-abdominal or pelvic tumors; diverticular, epidural, or psoas abscess; and the generally less worrisome diagnoses of herpes zoster or herniated lumbar disc. DIAGNOSIS OF KNEE AND HIP DISEASES AND SYNDROMES 3/31 6/11/2019 The majority of knee and hip problems can be diagnosed or excluded with a focused history and physical examination (Table 281-1). TABLE 281-1 Suggested Clues for the Dierential Diagnosis of Hip and Knee Pain Determine the location of the pain to narrow down the potential diagnosis. Determine the activities that bring on the pain. Complaints that the joint "gives out" or "buckles" generally are due to pain and reflex muscle inhibition rather than an acute neurologic emergency. This complaint may also represent patellar subluxation or ligamentous injury and joint instability. Poor conditioning or quadriceps weakness generally causes anterior knee pain of the patellofemoral syndrome; therapy should address this weakness. Locking of the knee suggests a meniscal injury, which may be chronic. A popping sensation or sound at the onset of pain is reliable for a ligamentous injury. A recurrent knee eusion aer activity suggests a meniscal injury. Pain at the joint line of the knee (palpable indentation between distal femur and proximal tibia) suggests a meniscal injury. IMAGING A suspected diagnosis obtained via history and physical examination is confirmed or ruled out by imaging. For the majority of so tissue injuries or overuse syndromes, radiographs are not particularly useful unless a history of significant trauma or cancer exists. More sophisticated imaging is typically not needed for evaluation in the ED but may be indicated at follow-up or for selected ED patients on an individual basis. US can identify intra-articular or bursal eusions and so tissue swelling and can localize muscle or tendon injuries. Normal comparison US views from the unaected leg can be helpful. US is very helpful for the evaluation of popliteal cysts and arterial structures and will exclude deep venous thrombosis as a cause of pain and swelling. Plain films are helpful in the evaluation of bony abnormalities such as severe arthritic changes and spurring, calcification derangements, and other inflammatory processes late in their courses. CT scan provides superior detail of osseous structures, will identify intra-articular loose bodies, and visualizes the early changes of osteonecrosis. Abnormalities of the labrum and joint capsule may also be seen. MRI, as the test of choice, precisely defines the anatomy of both the hip and knee and provides great detail for so tissue and bony abnormalities. MRI is usually obtained on an outpatient basis. Although not frequently ordered from the ED, bone scans may be useful for the assessment of a variety of infectious and inflammatory processes, including avascular necrosis. Ultimately, arthroscopy of the knee and hip allows direct visualization of intra- articular lesions and simultaneous treatment. SPECIFIC SYNDROMES AND DISEASES BY LOCATION See Table 281-2 for a summary of the most important conditions. 4/31 6/11/2019 TABLE 281-2 Selected Syndromes by Location Diagnosis Diagnosis Pain Location Category Nerve Meralgia paresthetica Anterolateral thigh pain or paresthesias entrapment Obturator nerve entrapment Groin and inner thigh pain Ilioinguinal nerve entrapment Groin pain Piriformis syndrome (sciatic nerve Buttocks and hamstrings pain compression by piriformis muscle) Hip bursitis Trochanteric bursitis Hip pain when lying on side or with hip abduction and Ischiogluteal bursitis adduction Iliopectineal and iliopsoas bursitis Ischial pain Anterior pelvis and groin, hip extension Knee bursitis Pes anserine bursitis Anterior medial knee pain Prepatellar bursitis Pain anterior to patella Hip overuse External snapping hip syndrome (coxa Posterior lateral hip pain syndromes saltans) Lateral thigh pain Fascia lata syndrome Knee overuse Patellofemoral syndrome (runner's knee) Anterior knee pain, worse with prolonged knee flexion syndromes Medial plica syndrome Anterior medial knee pain, knee snapping during repeated Iliotibial band syndrome or snapping knee flexion/extension syndrome Pain over lateral epicondyles, or snapping when iliotibial Popliteus tendinitis band passes over femoral condyle Patellar tendinitis (jumper's knee) Posterior lateral knee pain, worse on downhill exercise Quadriceps tendinitis Inferior patellar or proximal patellar tendon pain Popliteal (Baker) cyst Proximal patellar pain Posterior knee pain PSOAS ABSCESS The psoas muscle is susceptible to the hematogenous spread of infection from distant sites because of its rich blood supply and proximity to overlying retroperitoneal lymphatic channels.2 Staphylococcus aureus is the most common pathogen (80%); other less frequent pathogens include Serratia marcescens, Pseudomonas aeruginosa, Haemophilus aphrophilus, Proteus mirabilis, and enteric pathogens. Symptoms include abdominal pain radiating to the hip, flank pain, fever, and limp. Presentation

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