To test hip abduction/adduction, \201 x the pelvis to avoid pelvic tilt by placing one hand \201 rmly over the iliac crest (see Plate 9). Occasionally, pain at the end of abduction or internal rotation occurs with a bony block (solid \200\234end-feel \200\235). In an older patient this might suggest impingement of a marginal joint osteophyt e. Barlow \200\231s maneuver checks for congenital dislocation of the hips in babies. Flex and adduct the hips exerting an axial force into the posterior acetabulum t o demonstrate posterior dislocation. Greater retroversion (allowing excessive hip external rotation) usually occurs in cases of slipped femoral epiphysis. External rotation is accentuated when the hip is \202 exed. The slip (usually inferoposterior) is thought to occur in association with a period of rapid growth. Muscle activation tests Speci \201 c muscle activation against resistance can be used to e licit pain, but results need to be interpreted cautiously in the context of known hip disea se: \200 Hip adduction against resistance (sliding their leg inward toward the other against your hand) reproducing pain is a sensitive test for adductor longus tendo nitis, but may be positive in osteitis pubis, hip joint lesions, and other soft tissue lesi ons in the adductor muscles. \200 Test the psoas by resisted hip \202 exion while in sl ight internal rotation. Psoas bursitis or infection tracking along the psoas sheath is like ly to give intense pain with minimal resistance. Hip abduction (sliding the leg outwards against your hand) may be particularly painful in c ases of gluteus medius tears but also in trochanteric bursitis or intra-articular pathology . Palpate posterolateral structures Ask the patient to lie on their side and palpate the post erolateral struc- tures (see Figure 2.13): \200 Tenderness over the greater trochanter is usually well-localized although it may be anterior or posterolateral to the trochanter and refers a small way down the leg. The ischial tuberosity and its overlying bursa lie at the apex of the buttock. The soft tissues overlying the point where the sciatic nerve exits the pelvis is found midway between the ischial spine and the greater trochanter. There may be tenderness as a result of soft tissue lesions or trauma causing sciatic nerve entrapment (piriformis syndrome), which can lead to foot drop. A tender coccyx (coccydynia) can be palpated in this position. It can also be palpated (and the sacrococcygeal joint moved) from a bidigital examination, though this requires the index \201 nger to be placed inside the rectum, the thumb outside, the two digits then holding the joint. CHAPTER 2 Regional musculoskeletal conditions 100 Diagnostic procedures Radiographs An AP radiograph of the pelvis is a good initial screenin g test in patients with pelvic, hip, or thigh pain. AP and lateral lumbar spine \201 lms may be warranted. \200 The pelvis is a common site of involvement in myeloma, metastatic malignancy, and Paget \200\231s disease of bone (see Chapter 16). Established, but not early, sacroiliitis can be ruled out. The main differential diagnoses of the causes of sacroiliitis are: AS, psoriatic or reactive arthrit is, enteric arthropathy including Whipple \200\231s disease, brucellosis and other infectio ns, hyperparathyroidism and osteitis condensans ilii (sclerosis of the SI joint on the lowe r iliac side). \200 Widening of the symphysis in children may be a sign of congenital dis orders of development (e.g., epispadias, achondrogenesis, chondrodysplasias, hypophosphatas ia), trauma and hyperparathyroidism (see Chapter 16). Widening of the symphysis pubis, osteitis pubis (bone resorption and sclerosis) and osteiti s condensans ilii are signs associated with chronic pelvic pain in multiparous women. General osteopenia is a risk factor for general low bone mass measured by densitometry; however, it is not a sensitive or speci \201 c indicator of oste oporosis (i.e., may be osteomalacia or rickets). \200 Regional osteoporosis con \201 ned to the femur is nonspeci \201 c but may re \202 ect hip synovitis, infection, or transie nt osteoporosis of the hip (rare). Greater trochanter and site of overlying bursa Sacrum Coccyx Ishial tuberosity and site of overlying bursa Fig. 2.13 Bony anatomy of the posterior hip and pelvis, showing the position in which lesio ns around the greater trochanter and ischial bursa can be palpated. PELVIC, GROIN, AND THIGH PAIN 101 Early synovitis and infection may be demonstrated through subtle radiological signs such as joint space widening and change in soft tissue fat planes. A \200\234frog leg \200\235 (lateral) view of the hip shows the anterior and posterior femoral head more clearly than an AP view (useful in early osteonecrosis/Perthes \200\231, slipped epiphysis). The acetabulae are best visualized on 45 oblique views (acetabular fractures can be missed on a conventional AP view). \200\234Stork \200\235 views of the symphysis pubis (standing on one leg) are useful for con \201 rming diastasis of the joint. Diagnostic ultrasound \200 US is a sensitive and simple way of con \201 rming a hip join t effusion. Using US, \202 uid can be aspirated for culture and an assessment of the extent of synovi al thickening can be made. Tendon damage in the groin area should be identi \201 able with US alone (guided steroid i njection can then be done if necessary) but MR may be needed either to characterize patholo gy further or rule out joint pathology. Bone scan Bone scan is a useful screening test, but it is nonspeci \201 c: \200 Characte ristic, though nonspeci \201 c, patterns of bone scan abnormality are recognized in the hi p/pelvic area. The following conditions can be recognized: sacroiliitis, bone malignancy, m yeloma, Paget \200\231s disease, hip fracture, femoral head osteonecrosis (see Plate 10), o steoid osteoma, OA and synovitis of the hip, osteitis pubis/adductor apophysitis (requires special seated \200\234ring \200\235 view), and bursitis/enthesitis at the greater trochan ter. Bone scan is a useful investigation in children and adolescents as a screening investigation if other radiology tests are normal. CT and MR \200 CT/MR of the high lumbar region should be considered to con \201 rm a nerve root lesion, causing groin or thigh pain. Speci \201 c patterns of X-ray attenuation or signal change around the SI joints occur in sacroiliitis with CT/MR, although active and previous in \202 ammation cannot easily be di stinguished. A suspicion of bony malignancy from radiographs of the pelvis requires further characterization. CT is the technique of choice for characterizing bone le sions around the hip such as femoral neck stress fracture, osteoid osteoma, or other bone t umors. CT may give more information about the lesion (and is valuable for \200\234guided b iopsy \200\235) but MR is useful in checking for pelvic visceral lesions. MR is the technique of choice if hip infection or osteonecrosis is suspected. In adults, patterns of signal change have been correlated with prognosis. CHAPTER 2 Regional musculoskeletal conditions 102 During a single examination the pattern of hip synovitis (vascularity and thickness), carti lage loss, and subchondral bone erosion can be documented. This is particularly useful in c hildren with JIA. Laboratory tests \200 ESR and CRP may be normal in in \202 ammatory SI joints, lumbar vertebral disc, and pelvic enthesis disorders. PMR is almost always associated with an elevated ESR/CRP. \200 Myeloma is unlikely if the ESR is normal. \200 A high alkaline phosphatase is typically associated with an acute ph ase response, although in the elderly, it might suggest Paget \200\231s disease. ANA and RF are unlikely to help diagnostically. \200 Major metabolic bone disease such as osteomalacia and hyperparathyroidism is usually excluded by a normal serum calcium and phosphate. Treatment Treatment of spinal and neuropathic pain is covered in the section Low Back Pain and Disorders in Adults. \200 NSAIDs may be required for a number of the conditions just described, particularly OA, hip synovitis, and tendon in \202 ammation. Physical therapy and rehabilitation play a vital and early part in management, maintaining mobility, preventing tissue contracture, and restrengthening/stabil izing the lower back, pelvis, and hip. \200 Either physical therapists or podiatrists may help in accurately evaluating back and lower limb biomechanics. Asymmetry and muscular imb alance may be modi \201 able relatively simply with foot orthotics, for example. Steroid injections may be important in the following conditions: meralgia paresthetica \200 osteitis pubis \200 trochanteric bursitis/enthesitis \200 ischial bursitis/enthesitis \200 adductor tendonitis \200 coccydynia \200 hip synovit is (under imaging guidance) \200 sacroiliitis \200\224in intractable pain and under X-ray or US guidance. \200 Injection techniques are covered in Corticosteroid Injection Therap y at the end of this chapter. Surgery \200 When the hip has been damaged by an in \202 ammatory arthritis or OA, the p rincipal surgical intervention is joint replacement. Osteotomy has been mainly superseded b y more reliable replacement. Surgical synovectomy of the hip is a dif \201 cult procedure and opening the hip carries a risk of avascular necrosis. This procedure is very rarely done. PELVIC, GROIN, AND THIGH PAIN 103 Excision arthroplasty is only really necessary where infection or poor bone stock make reconstruction unwise. Power is often greatly reduced and even the pre viously \201 t young patient will not be able to ambulate without crutches. In children in particular, it is important to assess spinal and knee disease, especially co ntractures, before embarking on hip surgery, because the primary cause for \202 exion def ormities or hip damage may be at these levels. CHAPTER 2 Regional musculoskeletal conditions 104 Knee pain Anatomy of the knee \200 The knee extends, \202 exes, and rotates. \200 The main extensor quadriceps consists of four muscle segments \200\224 rectus femoris, vastus lateralis, medialis, and intermedius \200\224which converge to form a tendon containing the patella, which then inserts into the tibia. The rectus femoris arises from the pelvis and vastus muscles from the upper femur. The hamstring muscles (biceps femoris, semitendinosus, semimembranosus) all arise from the ischial tuberosity and \202 ex the knee. The biceps f emoris inserts around the \201 bular head. The other two muscles insert into the tibia on the medial side and can externally rotate the femur. In the knee, the femoral condyles articulate within semicircular \201 brocartilage menisci on the tibial condyles (see Figure 2.14). Only the peripheral 1 0 \200\22330% of the menisci is vascular and innervated and can potentially repair itself. As the knee approaches full extension, the femur internally rotates on the tibia (biceps fe moris action), tightening each pair of ligaments relative to each other (see Figure 2.14). This con \201 guration confers maximum stability. As \202 exion is initiated, a small amount of femoral external rotation on the tibia occu rs. This \200\234unlocking \200\235 is done by the popliteus \200\224a muscle that arises from the posterior surface of the tibia below. It passes up obliquely across the back of th e knee and inserts, via a cord-like tendon, into the lateral femoral condyle. The tendon pa rtly lies within the knee joint capsule. Grooves on the femoral condyle articular surfaces allow tight congruity with the anterior horns of the menisci when the knee is extended. If full extensi on \200\224and this optimal articulation con \201 guration \200\224is lost, then articular cartilage degeneration invariably follows. This is particularly important in in \202 amma tory arthritis. The cruciate ligaments are the principal joint stabilizers. The anterior cruciate attaches above to the inside of the lateral femoral condyle and below to the tibia in front of the tibial spines though a slip attaches to the anterior horn of the lateral m eniscus. Its main role is to control and contain the amount of knee rotation when the joint is \202 exed. \200 The posterior cruciate attaches above to the inside of the medial femoral condyle. At the other end, it attaches in a posterior groove between tibial condyle s. Its main role is to stabilize the joint by preventing forward displacement of the femur relative to the tibia when the knee is \202 exed. The cruciates are extra-articular and are covered by a layer of vascular synovium. Bleeding usually accompanies disruption. The tibial or medial collateral ligament (MCL) has super \201 cial and deep layers (see Fi gure 2.15). It stabilizes the knee against valgus stresses, mostly during \202 exion. The super \201 cial MCL overlies, and moves relative to, the deep part and is separated from it by a bursa. The lower part KNEE PAIN 105 Pull of cruciates rotates femur as knee AC extends AC Anterior cruciate ligament Lateral meniscus PC Medial meniscus Posterior cruciate ligament Fig. 2.14 Axial section of the right knee joint (looking down on the tibial plateau, where the foot is \201 xed on the \202 oor). The femoral condyles articulate within the menis ci. As the knee extends the cruciate ligaments tighten and pull the femoral condyles acting to internally rotate the femur through the last few degrees of extension. The knee therefo re \200\234locks \200\235 and is stable when the leg is straight. Patella Superficial prepatella bursa Deep prepatellar bursa Anterior cruciate ligament Lateral collateral ligament Medial collateral ligament Deep infrapatellar bursa Pes anserine bursa Superficial infrapatella bursa Fibula Fig. 2.15 Anterior knee structures. CHAPTER 2 Regional musculoskeletal conditions 106 of the super \201 cial MCL is covered by the long adductors, gracilis, semitendinosus, and sartorius muscles, as they merge into the pes anserinus before inserting into the tibia. T he MCL and pes anserinus are separated by the anserine bursa. Deeper MCL \201 bers attach to, and stabilize, the medial meniscus. The \201 bular or lateral collateral ligament (LCL) joins the lateral femoral condyle to the \201 bular head and is separated from it by a bursa. It stabilizes the kne e on its lateral side. It has no meniscal attachment. A small bursa separates it from the o verlapping tendon insertion of biceps femoris. The patella is a sesamoid bone that articulates in the femoral condylar groove and makes qu adriceps action more ef \201 cient. Patella articular facet con \201 guration can vary; c ongenital bi/tripartite patellae are associated with anterior knee pain. The strongest force on the patella is from vastus lateralis (see Figure 2.16). Mechanical factors that increase the ratio of lateral to medial forces d uring patella tracking such as a wide pelvis, a more lateral origin of vastus lateralis, fe moral neck anteversion, external tibial torsion, and a weak vastus medialis are risk factor s for patella tracking problems and anterior knee pain. There are bursae (see Figure 2.15) between the quadriceps tendon and the femur (suprapatellar), the patellar tendon, and tibial tubercle (deep infrapatellar ), and overlying the patella (prepatellar) and patellar tendon insertion (super \201 cial infrapatellar). The suprapatellar bursa communicates with the knee joint and large joint ef fusions invariably \201 ll it. Posteriorly, bursae separate each of the heads of gastrocnemius (which arise from femoral condyles) from the joint capsule. The bursae communicate with the knee joint and can \201 ll from joint effusions. Taking a history Ask about the site of pain Try to establish whether pain is from articular , soft tissue, or anterior knee structures. Is it referred pain? \200 Bursa, tendon, and most ligament lesions cause well-localized pain. \200 Localized tibiofemoral joint line p ain suggests meniscal pathology. \200 Localized medial knee pain has a number of possible causes: MCL tear or chronic in \202 ammation (calci \201 cation of MCL origin termed the Pellegrini \200\223Stieda phenomenon), medial meniscus tear, meniscal cyst, anserine tendo nitis, bursitis, or enthesitis (semimembranosus insertion). Enthesitis of structures at their insertion to the patella margins can result in considerable pain. Overuse in runners and cyclists can cause localized in \202 ammation and pain of the iliot ibial band (ITB) or its underlying bursa over the lateral femoral condyle (as the band move s across the bone as the knee \202 exes). Anterior pain in children, adolescents, and young adults invariably suggests an underlying mechanical abnormality. In older adults the most common cause is patellofemoral OA (see Tab le 2.19). KNEE PAIN 107 (a) (b) Anterior superior iliac spine Iliotibial band Vastus lateralis Lateral condyle of femur Midpoint of patella Iliotibial band insertion at tibia Lateral view of the thigh Q angle Fig. 2.16 (a) The iliotibial band. (b) The patella Q angle (normal values \200\224men 10 , women 15 ). Anterior knee pain may be referred from the hip or L3 nerve root. Hip pain is an aching pain; root pain is sharp, often with paresthesias. Posterior knee pain associated with \200\234a lump \200\235 is often due to a Baker \200 \231s cyst, which is caused by synovitis in the posterior knee compartment that leads to fo rmation of a popliteal cyst. Ask about injury Knee injuries are common; the most signi \201 cant is anterior cruciate i njury. Ask about injury and whether the knee feels unstable or \200\234gives way \200\235. \200 Anterior cruciate injuries are invariably associated with a hemarthrosis, thus a pa inful effusion will have occurred immediately. Meniscus tears can cause immediate pain, but synovitis and swelling are delayed for about 6 hours. Patients may mention that the knee \200\234keeps giving out on me \200\235. This feeling may be the pivot shift phenomenon caused by reduced anterior cruciate stability aga inst a valgus stress as the knee is \202 exing. \200 Anterior cruciate and MCL injuries often coexist (since they are attached). Ask about medial knee pain originally and subsequently. CHAPTER 2 Regional musculoskeletal conditions 108 Table 2.19 Causes of anterior knee pain Commonly in adults Patellofemoral OA (look for mechanical factors and generalized OA) Referred hip pain, e.g., hip OA Referred pain from L3 nerve root irritation Speci \201 c to children and adolescents Referred pain from the hip, e.g., slipped femoral epiphysis Bi-/tripartite patella Synovial plicae (synovial shelf clicking over femoral condyle on knee \202 exion) Recurrent patellar dislocation (tissue laxity, patella alta, trauma) Osteochondritis at patellar lower pole \200\224overuse injury in jumping sports* Osteochondritis of tibial tubercle (Osgood \200\223Schlatter \200\231s) Nonspeci \201 c ( \200\234chondromalacia patellae \200\235) Causes at any age Mechanical factors (patellar maltracking): wide pelvis, femoral anteversion, external tibia l torsion; speci \201 c strengthening of lateral structures, e.g., iliotibial band syndrom e; weakness or injury of vastus medialis or medial knee structures; tissue laxity, e.g., be nign joint hypermobility syndrome Osteochondritis dissecans of patella (average age 18) Enthesitis at patellar margins (may be part of SpA) Bursitis (prepatellar, super \201 cial/deep infrapatellar): gout (very rare in children un less inherited metabolic de \201 ciency); autoimmune rheumatic disease; infection Tear/cyst of anterior meniscal horn Patellar fracture Fat pad syndrome (recurrent retropatellar tendon pain with swelling) Sinding \200\223Larsen \200\223Johansson disease. Ask about knee locking Knee locking is a mechanical effect of disruption of normal articula tion by \200\234loose bodies \200\235. \200 Suspect meniscus damage in the middle aged o r if the patient plays a lot of sports. A meniscus tear is the most common cause of the kne e locking. In adolescents, locking may be due to a tear in a discoid meniscus (>98% lateral ). The morphologically abnormal disks are prone to degeneration. KNEE PAIN 109 Chondral fragments (from osteochondritis dissecans lesions) can cause locking; the conditio n is most common in the 5 \200\22320 year age group (boys > girls). Synovial chondromatosis is a rare cause. \200 Some patients with anterior knee pain descr ibe the knee locking or giving way. This is due to re \202 ex quadriceps inhibition rather than true instability. Ask about the initial onset of pain \200 Acute pain is usual with injuries of cruciates a nd vertical meniscal tears. \200 Acute onset pain without trauma (but always with swellin g) suggests infection, crystal arthritis, or spontaneous hemarthrosis. In the very elderly, traumatic lesions may be missed, since the presentation is not always striking, e.g., intra-articular fracture with hemarthrosis. An insidious onset of pain is usual in cleavage tears of menisci (i.e., horizontal tears), which occur typically in adults where the disc is degenerated, in adolescents with discoid menisci, and in early osteochondritis dissecans. Ask about the pattern and type of pain \200 Pain from synovitis is often associated with stiffness and is often worse after a period of immobility. Almost without exception, knee s ynovitis can occur in all forms of arthritis. Pain from subchondral damage (e.g., OA) is almost always worse on weight bearing, but this association is not speci \201 c. Pain on kneeling/squatting is characteristic of anterior knee pain. \200 Burning pain may be neurogenic, e.g., L3 nerve root or re \202 ex sympathetic dystrophy pain. Past medical, family, occupational, and leisure history \200 Knee synovitis and patellar enthesitis occur in adult and juvenile enthesitis-related arthritis. Ask about previous uve itis, low back pain, urethral discharge, sexually transmitted disease, dysentery, and psori asis. Gout (see Chapter 15) is not uncommon around the knee. Ask about gout risk factors and whet her the patient has ever had \201 rst MTP joint pain (i.e., podagra). There may be a family history of generalized OA (see Chapter 6), a hereditary disease of connective tissue, or hypermobility in young adults with OA. Prepatellar bursitis classically occurred in housemaids, hence the nickname \200\234housemaid \200\231s knee. \200\235 Friction from repeated kneeling can ca use it. Sports injuries are common. Anterior cruciate injury is a typical skiing injury. Meniscal i njuries are common in soccer. Jumping events (e.g., high jump, basketball) can lead to pate llar tendon apophysitis. Cycling is associated with anterior knee pain. MCL and meniscal in juries are common in skiing and weight-bearing activities where rotation and change of dire ction are frequent. Cycling and running are associated with ITB/bursa pain and in \202 amm ation. CHAPTER 2 Regional musculoskeletal conditions 110 Examination From front and behind, observe the patient standing \200 Look for mechanical abnormalities that might be associated with knee lesions: patella asymmetry, prominent tibi al tubercles from previous Osgood \200\223Schlatter \200\231s (anterior knee pain), \202 at feet, and hypermobility (patella dislocation, hyperextension of >10 ). Check for mechanical abnormalities, which might suggest speci \201 c pathology: genu varum (bowed leg, typical appearance with primarily medial compartment OA), obvious suprapatellar knee swelling (synovitis), psoriasis (associated synovitis or enthes itis). Marked genu varum occurs in the rare Blount \200\231s disease (developmental abnormality of the medial tibial physis typically in African-American boys). Examination of the sitting patient Ask the patient to sit on the examination table with leg s hanging, knees bent. Patellar tracking and pain from medial meniscus damage can be assess ed. An alternative approach is with the patient supine. Observe any muscle wasting. Palpate anterior, medial, and lateral structures. \200 In patients with anterior knee pain, look for symmetric patellar alignment. Observe active knee extension. Patellar movement should be smooth, pain-free, and symmetric. Passively externally rotate each lower leg to its extreme. This is a reasonably sensitive t est for conditions of the medial knee compartment (e.g., meniscus tear) and medial knee str uctures. Discomfort will be felt. If the MCL is totally de \201 cient, an abnormally incre ased range of external rotation may occur. Quadriceps wasting (accentuated depression in muscle just above the patella) occurs with di suse after injuries and in chronic arthropathies. Sites of bursae, patellar tendon, and ligament insertions should be palpated in patients with localized pain (see Figure 2.17). Tibiofemoral joint line tenderness is likely to be due to either meniscus pathology or marg inal osteophytes. Osteophytes give bony swelling. Anterior pain from patellofemoral joint disorders may be elicited by gentle pressure down o n the patella. Mobilizing the patella sideways will give an impression of tissue laxity (po ssible underlying hypermobility). Factors that predispose to patellofemoral pain syndrome include: a high or lateral patella, weak vastus medialis, excessive pronation, weak ankle dorsi \202 exors, tight hamstrings, reduced movement at the ankle, and a wide Q-angle. The Q-angle is formed between a line from the anterior superior iliac spine to the center of the patella, and a line extended upwards from the tibial tubercle through the center of the patella. The larger the angle the greater the lateral tensile pull on the patella (see Figure 2.15). Localized tenderness of the femoral condyle is often the only sign of osteochondritis dissecans in adolescents. The most common site is on the inside of the medi al femoral condyle (75%). KNEE PAIN 111 Examine for joint synovitis (synovial in \202 ammation giving synovial thickening and/or t enderness) and an effusion \200 The joint may be warm. Chronic synovitis does not always result in a warm joint, but infection, crystal arthritis, and hemarthrosis usually do. Gross synovitis can produce obvious effusions and/or synovial thickening most easily felt around the patellar edges. Effusions may be con \201 rmed by the patellar tap test (see Plate 11). (a) Edge of lateral femoral condyle Infrapatellar tendon Tibial tubercle (b) Adductor tubercle Edge of medial femoral condyle X Tibial plateau Fig. 2.17 Position of the knee for palpation of most of its structures. Palpating for enthe sitis at the patellar tendon insertion (a) Palpation over the insertion of semimembranosus and pes anserinus under the tibial plateau (b) The site of the majority of osteochondritis lesions in the knee is shown by the X. CHAPTER 2 Regional musculoskeletal conditions 112 Small effusions can be detected by eliciting the \200\234bulge sign \200\235. Fluid in the medial compartment is swept \201 rmly upward and laterally into the suprapatellar pou ch. Firm pressure on the lateral side of the joint may then push \202 uid back into the m edial compartment, producing a bulge. \200 Thickened synovium can be detected by experien ced examiners in the absence of a detectable effusion. It is not always tender. Posterior compartment synovial thickening and popliteal cysts can be felt by wrapping the \201 ngers around under the knee when it is slightly \202 exed. In contrast to adults, popliteal cysts in children are not usually associated with intra-articular pathology. Investigation is not always necessary. Test the knee for stability \200 There are many tests for instability: instability may be straight or rotational and can be graded according to consensus criteria (consult orthopedics texts). The Lachman test (see Figure 2.18) is arguably the most sensitive test for eliciting anteri or cruciate disruption: hold the knee \202 exed between 20 \200\22330 , grasped above an d below the joint. Attempt to move the tibia forward and backward on the femur. Ask about p ain and feel for laxity or a \200\234clunk \200\235. The anterior draw test is not as sensitive as the Lachmann test for detecting partial anterior cruciate tears but is easier to do. The patient lies \202 at, hip \202 exed, the knee \202 exed at 90 , with the foot \202 at on the table. Fix th e foot by gently sitting on it and pull the top of the lower leg forwards in the line of th e thigh. Ask about pain and feel for laxity. \200 The posterior draw test identi \201 es posterior cruciate disruption: with the knee \202 exed to 90 , press the top of the lower leg backward in the line of the th igh, ask about pain and feel for laxity. Test medial stability at 0 and 30 of \202 exion (MCL stabilizes maximally at 30 ) by holding the upper leg still and applying a valgus force to the tibia. Laxity associated wi th widening of the tibiofemoral joint (with or without pain) is a positive test and suggest s MCL de \201 ciency. Lateral (LCL and ITB) stability is similarly tested by using a varus force on the lower leg. MCL tears can accompany anterior cruciate injuries and deep lesions are associated with sim ultanous tears of the medial meniscus. Such complex pathology can make speci \201 c examin ation maneuvers dif \201 cult to interpret. Test for meniscus damage \200 McMurray \200\231s test (see Figure 2.19): Flex the knee, i nternally rotate the lower leg, then extend the joint. Repeat with the lower leg externally rotated. The \201 ngers (over the joint line) may feel a \200\234clunk \200\235 as a fe moral condyle passes over a torn meniscus. Unfortunately, a false-positive McMurray \200 \231s test is not uncommon, and may occur in 21 \200\22365% of cases. \200 Ask the patien t to turn over. Lying initially on their side allows you to do Ober \200\231s test to detec t lateral soft tissue injury. When prone, look and palpate for swelling in the popliteal fo ssa and proximal calf that may indicate a low-lying popliteal cyst. KNEE PAIN 113 Anterior draw test Pull tibia forward Sit on foot to fix Lachmann test 20 \200\22330 Fixed Move tibia up and down relative to femur Fig. 2.18 Dynamic tests of anterior cruciate function. Patients should be relaxed lying sup ine on a couch. Excessive laxity is the most important sign. McMurray \200\231s test 1 2 Action: Hold the knee and the heel. Internally rotate the lower leg (1) then extend it (2) Positive test: (Palpable) clunk at joint line Fig. 2.19 Dynamic test designed to elicit signs of meniscus damage. \200\234Clunks \200 \235, intra-articular pain, and coarse crepitus may indicate damage. The test is not speci \201 c and is open to misinterpretation. CHAPTER 2 Regional musculoskeletal conditions 114 In \202 ammation of the bursa underlying the iliotibial band (ITB) may result in tendernes s over the lateral femoral condyle. The ITB may be tight. This is demonstrated using Ober \200\231s test. The patient lies on his or her side with the lower (nonaffected) leg \202 exed at the hip. The (painful) knee is \202 exed to 90 and the thigh is extended and a dducted. The test is positive if, when the examiner \200\231s hand is removed, the hip does not drop down (further stretching the ITB). Leg length inequality and foot overpronation m ay be causative factors. Detecting speci \201 c structures in the posterior fossa is often dif \201 cult because o f the lack of bony landmarks and overlapping soft tissue structures. Synovial cysts may for m under pressure and are often hard and tender. Diffuse thickening suggests joint synovitis . Diagnostic procedures Radiographs AP and lateral weight-bearing radiographs are suitable sc reening views if the diagnosis is unclear after clinical assessment. \200 Early synovitis may only be evident from the presence of an effusion, periarticular osteopenia, or soft ti ssue swelling. Patterns of bone damage in chronic arthropathies may be recognized. Signs of joint infection, which may not necessarily present acutely, are patchy bone osteol ysis and irregular loss of bone cortex. Osteonecrosis is uncommon in the knee, but it does occur in sickle cell anemia. Loss of joint space, angulation deformity, osteophytes, subchondral bone sclerosis, and bone cysts are hallmark features of OA. \200 In adults, linear or vag ue intra-articular calci \201 cation suggests chondrocalcinosis (associated with calcium pyrophosphate dihydrate (CPPD) arthritis). Gross \200\234thumbprint \200\235 calci \201 cation is typical of synovial chondromatosis (mai nly in children). In children, check for an osteochondral fragment (e.g., osteochondritis dissecans), normal epiphyses, epiphyseal plates and metaphyses, normal patella shape, and o steochondritis at the tibial tubercle (see Table 2.20). Specialized radiographic views: tomographic views; \200\234skyline \200\235 (axial with kn ee bent) view; or lateral view taken with at least 30 of \202 exion \200 Tomography i s useful for clarifying nonperipheral osteochondral defects. \200\234Sunrise \200\235 views demonstrate anomalous patellar facet con \201 guration and can reveal patellofemoral incongruity, but multiple views may be needed. Subchondral patel lar pathology is seen more clearly with a sunrise view than on lateral views. Patella alta is most reliably seen on a lateral view with 30 \202 exion. Further imagin g Further imaging depends on the differential diagnosis and a discussion with your radiolog ist: \200 Periarticular soft tissue lesions can be characterized with MR, but ultrasound may be adequate (if performed by someone with expertise in this area). KNEE PAIN 115 Table 2.20 Interpretation of radiographic knee abnormalities in children Radiographic abnormality Possible conditions (most commonly) Intra-articular calci \201 c fragment Osteochondritis dissecans, traumatic avulsion, synovial tumors, or chondromatosis (rare) Epiphyseal defect/abnormality JIA, sepsis, avulsion injury, bone dysplasias, rickets, hemophilia, hypothyroidism Transverse radiolucent metaphyseal band or lysis Leukemia, lymphoma, neuroblastoma metastases, infections (neonates), osteogenesis imperfect a, idiopathic juvenile osteoporosis, Cushing \200\231s disease Joint space narrowing JIA, sepsis, PVNS, hemophilia Diffuse low bone density Rickets, OI, osteoporosis, mucopolysaccharidosis Periosteal reaction Fracture, sepsis, infarction, tumors Patterns of meniscus damage are recognized on MR, give an indication of prognosis, and aid the surgeon \200\231s decision to proceed to arthroscopy. MR is essential if there is likely to be a combination of lesions (e.g., anterior cruciate, MCL, and medial meniscus lesions). In children, both US and MR will con \201 rm synovitis. \200 MR is more sensitive than r adiographs or US at identifying joint erosions in RA. The place of CT or MR in investigating radiographically detected bone tumors depends on the nature of the lesion. Aspiration of joint and periarticular \202 uid collections \200 Early aspiration is ess ential if infection is suspected. \200 The knee is a common site of monoarthritis. The pr inciples behind management apply to all cases of single joint pathology. Send joint \202 uid for cell count, polarized light microscopy, and culture. \200 In ad ults, the usual differential diagnosis of sepsis of knee structures is gout, so \202 uid should be examined by polarized light microscopy for urate crystals. Blood-stained \202 uid either suggests a traumatic tap or chondrocalcinosis. Frank blood suggests hemarthrosis, the major causes of which are cruciat e tear, bleeding diathesis, intra-articular fracture, and pigmented villonodular synovitis (PVNS). Bursa \202 uid may be more successfully detected and aspirated using US guidance. Laboratory tests These should be directed toward suspected underlying disease: \200 CBC, acute phase reactants (ESR, CRP). \200 Electrolytes, BUN, creatinine, and uric acid. CHAPTER 2 Regional musculoskeletal conditions 116 Blood calcium, phosphate, albumin, alkaline phosphatase, and 25-OH vitamin D ( iPTH) to screen for metabolic bone disease. Autoantibodies: rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPA) are found in rheumatoid arthritis; antinuclear (ANA), and extractable nuclear antibodies (ENAs ) are found in SLE and other autoimmune diseases that may be include joint involvement. Serum angiotensin converting enzyme (sACE) for sarcoid. \200 Infection: IgM Borrelia burg dorferi serology for acute arthropathy in Lyme disease, acute and convalescent streptococcal antibodies (anti- ASO titers) for reacti ve streptococcal arthritis. Treatment \200 In general, most soft tissue lesions will improve with rest and NSAIDs. \200 Anterior knee pain may respond well to isometric exercises, adjustments to foot alignment, e.g., with sensible shoes, orthotics (support insoles), and hamstring stretching exercises. The acute swollen knee requires aspiration, rest for 24 h and gentle mobilization. If infection is considered, broad-spectrum antibiotics against staphylococcus (including MRSA, if relevant) and streptococcus should be started immediately while awaiti ng culture data. In infection, intra- articular antibiotics and steroids should be avoided (see Chapter 22). The patient should not bear weight on an acutely infected joint. \200 A cute and chronic in \202 ammation can lead to joint destruction and instability. If RA is identi \201 ed, early treatment may prevent long-term morbidity (see Chapter 5). Physical therapy and splinting play an important role in maintaining function and preventing contractures, etc. Address biomechanical factors \200 Input from a physical therapist may be helpful in case s of anterior knee pain. Success from McConnell (patellar) taping is more likely in nonpatellofemoral OA- related anterior knee pain. Quadriceps strengthening exercises can be reviewed and reinforced by physical therapists in cases of knee OA. Knee pain, particularly anterior pain, may be linked to foot abnormalities (e.g., overpronation), and hip alignment (see Q-angle, above). \200 Speci \201 c muscle strengthening exercises, foot orthotics, and knee braces should be considered. Local steroid injection Local steroid injections can be helpful in the following situations : \200 Acute \202 are of non-infective in \202 ammatory disease: OA (especially where CPPD is present) \200\224mild OA may also respond to hyaluronate injections, although this is controversial autoimmune arthritis, e.g., RA, SpA \200 intra-articular gout \200 SpA, etc. Bursitis (may be gout): pre- and infrapatella (super \201 cial and deep) bursa (the latter may require US guidance) anserine. KNEE PAIN 117 Baker \200\231s cyst (note: the knee joint is injected with corticosteroids, since the join t and the cyst are connected. Direct popliteal cyst injection should be performed under US guidance only). \200 Enthesopathy, e.g., semimembranosus insertion. \200 Trauma, e.g., pain over the medial collateral ligament insertion. \200 Other soft-tissue: ITB syndrome. The reader is referred to Corticosteroid Injection Therapy at the end of this chapter. Joint injection therapies \200 In patients with large joint effusions, merely aspirating the effusion may provide some level of symptomatic relief