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 Knee OA may respond transiently to an injectable steroid, such as triamcinolone acetate. Saline irrigation and injections with hyaluronic acid preparations a re also used, but response is variable. Note: all intra-articular injection therapies are more effective when patients \200\231 kne es are immobilized for 48 hours following the procedure. Drugs \200 NSAIDs will invariably be helpful in cases of in \202 ammatory and septic arthritis. Colchicine 0.6 mg BID is often useful in relieving pain from crystal arthritis in patients intolerant of NSAIDs. Acetaminophen may be as effective as NSAIDs for some patients \200 Glucosamine and chondr oitin sulfate are controversial for the treatment of osteoarthritis. Although some studies demonstrate improved pain control and fu nction, other studies clearly indicate that these drugs are no better than placebo. See Part 2 chapters for speci \201 c treatment of chronic autoimmune arthritides. Surgery \200 Arthroscopy is often used as a diagnostic tool in cases of undiagnosed monoa rthritis and to con \201 rm and trim cartilage tears. Synovium and synovial lesions (e.g., PVNS, synovial chondromatosis) can be biopsied or excised (synovectomy) and the joint can be irrigated. In appropriate cases joint replacement can be remarkably successful and is an important opt ion to consider in OA and in \202 ammatory arthritis where pain is severe and present at r est, and when mobility is substantially restricted. Arthrodesis is rarely indicated. \200 Unicondylar osteotomy can aid realignment of the ti biofemoral joint, e.g., in metabolic bone disease such as Paget \200\231s disease. Other \200 In OA, capsaicin cream applied three or four times daily to the joints can eas e symptoms. Response is cumulative, and may not occur for 6 \200\2238 weeks. Topical diclofenac gel may also be useful for the treatment of symptomatic osteoarthritis of the hands and knees. CHAPTER 2 Regional musculoskeletal conditions 118 Lower leg and foot disorders (adults) Anatomy Anatomy of bones and joints \200 The leg ab sorbs six times the body \200\231s weight during weight bearing. Strong ligaments secure the ankle (formed by the tibia above/medially and \201 bular mall eolus laterally) and talocalcaneal (subtalar) joints and bones of the midfoot (see Figure 2 .20). Anomalous ossicles in the foot are common. Some are associated with speci \201 c pathology . There are many potential sites, but the sesamoids in \202 exor hallucis brevis (FHB) ar e invariable. The foot is an optimal mechanical device to support body weight when walking or running over \202 at, inclined, and uneven types of terrain. The con \201 guration of bones at synovial articulations allows dorsal \202 exion (foot pulled up ), plantar \202 exion (to walk on toes), inversion Transverse mid tarsal joint of Chopart Talus Navicular Tarsometatarsal joint of Lisfranc Metatarsals Medial view Calcaneus Phalanges Cuneiforms Hindfoot Midfoot Forefoot Hindfoot Transverse mid tarsal joint of Chopart Cuboid Tarsometatarsal joint of Lisfranc Navicular Lateral Middle Medial Midfoot Cuneiforms Sesamo ids Dorsal view Hallux Forefoot Digits Fig. 2.20 The bones of the foot. Fracture or dislocation at Lisfranc \200\231s and Chopart \200\231s joints may occur as the result of motor vehicle accidents, falls from a height, o r sports injuries (e.g., basketball). LOWER LEG AND FOOT DISORDERS (ADULTS) 119 (foot tips in), eversion (foot tips out), and small degrees of adduction and abduction. Mid foot movements allow pronation and supination. \200 The normal ankle joint range is about 25 of dorsal \202 exion and 50 of plantar \202 exion from neutral (foot 90 to le g). The range of subtalar inversion \200\223eversion is normally 10 \200\22315 . Anatomy of the long muscles and tendons \200 In the lower leg, a strong fascia connects t he tibia and \201 bula. Lower leg muscles primarily move the foot. They are separated into compartments by fascia and are prone to pressure effects. The foot dorsal \202 exors \200\224tibialis anterior, extensor digitorum longus (EDL), ex tensor hallucis longus (EHL) and peroneus tertius \200\224lie adjacent to the anteromedial side of the tibia. Their tendons pass in front of the ankle in synovial sheaths held down b y strong retinaculae (see Figure 2.21). The tibialis anterior, the bulkiest \202 exor, in serts into the medial midfoot (medial cuneiform). In the posterior lower leg, the gastrocnemius (and plantaris), which arise from the femur, plantar \202 exes the foot by pulling the back of Lateral view of ankle Superior exterior retinacula Lateral malleolus Common sheath of peroneus longus and brevis tendons Inferior extensor retinacula Retrocalcaneal bursa Sheath of extensor digitorum longus and peroneus longus tendons Subcutaneous calcaneal bursa Superior and inferior peroneal retinacula Subcalcaneal bursa Medial view of ankle Tibia Sheath of flexor digitorum longus Posterior tibial artery Posterior tibial nerve Flexor retinaculum Sheath of flexor digitoru m longus Posterior tibial tendon end sheath Fig. 2.21 Tendons, retinaculae, and bursae of the hindfoot. CHAPTER 2 Regional musculoskeletal conditions 120 the calcaneum. The soleus, which arises in the lower leg, merges with them in the Achilles tendon. This tendon has a deep and super \201 cial bursa at its insertion site. Plantar \202 exion is assisted weakly by long muscles, which arise in the lower leg, pass behind the medial malleolus in synovial sheaths (see Figure 2.21), and insert into the sol e. They mostly invert the foot. Tibialis posterior, the most bulky plantar \202 exor, ins erts into the plantar surface of the navicular. The peroneus longus and brevis arise from the \201 bular side of the leg and pass around the lateral malleolus in a common synovial sheath held by a retinaculum. Longus passes into the sole and inserts into the medial cuneiform. Brevis inserts into the \201 fth metatar sal base. Both evert the foot. The tibial nerve and artery follow the course of the medial tendons under the \202 exor retinaculum (see Figure 2.21). Anatomy of intrinsic foot structure \200 Intrinsic foot structures have been greatly modi \201 ed during evolution to combine provision of a \202 exible platform for support and a rigid lever for thrusting body weight forward when walking. In the sole of the foot, muscles are aligned longitudinally in four layers. The deepest lay ers include phalangeal interossei in the forefeet, tibialis posterior, peroneus longus, add uctor hallucis, and FHB \200\224which has two insertions into the proximal great toe phalan x, each containing a sesamoid. The super \201 cial layers include \202 exor digitorum longus (FDL), which inserts into the lateral four distal phalanges, the phalangeal lumbricals, \202 exor digi torum brevis, and abductor hallucis. The latter two muscles arise from the plantar surface of the calcaneum deep to the plantar fascia. Flexor tendons merge with the deeper part of the plantar fascia, a swath of tissue that ext ends from os calcis to the metatarsal area. \200 Longitudinal muscles, ligaments, and fas cia contribute to stabilize the foot with a longitudinal arch \200\224its apex at the talus but also with some effect l aterally. The foot arches transversely \200\224its apex at medial cuneiform level. Neuroanatomy \200 The sciatic nerve splits into tibial and common peroneal nerves above t he knee. The common peroneal is prone to pressure neuropathy as it runs super \201 cially around the \201 bular head. The nerve then divides. A deep branch runs distally with the EDL under the extensor retinaculum to the foot. It supplies tibialis anterior, EHL, and EDL . A super \201 cial branch supplies the peroneal muscles and most of the skin over the dor sum of the foot. The tibial nerve runs in the posterior lower leg compartment supplying the gastrocnemius an d soleus. It then passes under the medial \202 exor retinaculum, dividing into medial and lateral plantar nerves, which supply the intrinsic plantar muscles of the foot and skin of the sole. LOWER LEG AND FOOT DISORDERS (ADULTS) 121 Functional anatomy \200 In a normal gait pattern, the foot is dorsi \202 exed and invert ors/evertors stabilize the hindfoot for heel strike. As weight is transferred forward, the foot plantar \202 exes and pronates, the great toe extends (optimally between 65 and 75 ), and push off occurs through the medial side of the forefoot. All metatarsals bear weight and can suffer weight-bearing injury. \200 Ligamentous attach ments around the hindfoot are strong. A fall on a pronated inverted foot without direct tra uma can result in a fracture of the distal \201 bula. This is probably a consequence of t he relative strength of the talo \201 bular ligaments compared with bone. Developmental factors \200 Developmental characteristics often imply that different age g roups are prone to a different spectrum of conditions. Due to ligamentous laxity, when babies begin to walk, the midfoot is \202 at to the \202 oor. A longitudinal arch usually develops by 5 years. \200 During growth, tendon ins ertions (apophyses) are often weaker than the tendons themselves. Traction strain on tendons can lead to apophysitis (osteochond ritis). This is a common pattern of injury in the foot in active older children. Conditions of the lower leg \200 Patients with lower leg conditions may present with pain or deformity alone. In children, deformity may typically be due to spinal dysraphism (from birth), rickets (acquired age 1 year plus), or osteogenesis imperfecta (see Chapter 16). Pains in the calf may be due to local soft tissue or muscle conditions. In adults, calf pai n may be due to claudication or referred lumbosacral pain ( \200\234pseudoclaudication \200 \235). These pains are often described by patients as \200\234cramps \200\235 \200\224sugg esting a muscle problem at \201 rst. A detailed history may suggest the correct diagnosis . Imbalance of muscles in the foot can lead to increased tension at tendon and fascial insert ions in the calf and shin, resulting in \200\234shin splints \200\235. Shin splints usuall y present after activity and are relieved by rest. Conditions to consider include: \200 s tress fractures of the tibia or \201 bula \200 tibialis posterior fasciitis \200\224oft en associated with a \202 at, pronated foot compartment syndrome (soft tissue and vascular swelling) \200 popliteal artery stenosis \200 referred nerve pain (spinal claudication) \200 peripheral vascular disease (intermi ttent claudication). Taking a history Ask about site and quality of pain in the lower leg \200 Localized anter ior pain occurs in bony lesions of the anterior tibia, e.g., stress fractures, periostitis, etc. (see \200\234shin splints \200\235 in the preced ing section, Condition of the Lower Leg). CHAPTER 2 Regional musculoskeletal conditions 122 Burning pain suggests a neurogenic cause. Diffuse burning pain may be caused by peripheral neuropathy, complex regional pain syndrome (see Chapter 18), or (ra rely) erythromelalgia. Most commonly occurring in the elderly, bilateral leg pain with \200\234heaviness \200\235 or \200\234stiffness \200\235 limiting walking distance is typ ical of spinal stenosis. An alternative would be vascular claudication where often pain is more overt, and critical ischemia can give night pain eased by hanging the legs over the si de of the bed (gravity effects). Simultanous knee problems may be relevant. Escape of synovial \202 uid from the knee into the soft tissues of the calf can present with acute pain and swelling and be misdiagnosed as a deep vein thrombosis ( \200\234pseudothrombophlebitis \200\235). Often a history of pr eceding joint effusion can be elicited. Low-lying synovial cysts connecting with the knee can cause calf pain (with or without swel ling). This invariably occurs only with chronic synovitis. Establish possible causes of hindfoot pain (see Table 2.21) \200 Establishing the cause o f hindfoot pain from the history alone is dif \201 cult. There are important clues, mainly from patterns of injury or overuse. Posterior heel pain has a few causes. Often clinically indistinguishable from Achilles tend onitis or retrocalcaneal bursitis, enthesitis is usually associated with SpA (see Chapter 8 ). An os trigonum may become damaged especially in soccer players and ballerinas. The origin of plantar heel pain is varied. Mechanical plantar fasciitis is thought to occur more frequently in people who are on their feet for long periods of time, those who are ob ese, have thin heel fat pads, or poor footwear. Symptoms of arthritis and enthesopathy else where, low back pain (sacroiliitis), eye in \202 ammation (iritis), psoriasis, or previous gut or urethral infection, might suggest SpA. Less common causes of plantar heel pain include fracture through a calcaneal spur and later al plantar nerve entrapment between the fascia of abductor hallucis and quadratus plantae m uscles (causing pain/ paresthesias on the lateral side of the sole). In the elderly and postmenopausal women, calcaneal stress fractures are a recognized featur e of osteoporosis (see Chapter 16) and can present with heel pain. Ankle and talocalcaneal synovitis, OA, ankle osteochondritis dissecans, and tendonitis arou nd the hindfoot may be dif \201 cult to distinguish from the history alone. Synovitis or a n effusion often accompanies OA of these joints. Establish poss i ble causes of midfoot and \201 rst MTP pain \200 Gout (see Chapter 7), OA (see Chapter 6), enthesitis, and referred L5 nerve root pain are the most likely diagno ses of midfoot and \201 rst MTP pain. Any joint may potentially become involved in the major chronic arthropathies. Gout should always be considered a possible cause of painful lesions in the foot in people at risk. Gout is not always intra-articular, intrabursal, LOWER LEG AND FOOT DISORDERS (ADULTS) 123 Table 2.21 Common conditions causing localized foot pain in children, adolescents, and adul ts Site of pain Common lesions Ankle region Ankle or talocalcaneal joint: synovitis (e.g., gout), OA. L4/L5 root pain Posterior heel Achilles tendonitis. Retrocalcaneal bursitis. Achilles enthesitis. Osteonecrosis of os trig onum Medial side of heel As for ankle region. Calcaneal fracture. Tibialis posterior tendonitis. Plantar fasciitis. Lateral side of heel As for ankle region. Calcaneal fracture. Peroneal tendonitis. Fifth metatarsal base fractur e* Underneath heel Plantar fasciitis. Calcaneal fracture. Infracalcaneal bursitis. Lateral plantar nerve entra pment Top of foot Midfoot joint synovitis (e.g., gout), OA. Navicular osteochondritis. Enthesitis. L5 root pa in Sole of foot S1 root pain. Plantar fasciitis. Metatarsal stress fracture. Tibial/plantar nerve entrapmen t Toes MTP synovitis (e.g., RA, gout). MTP OA. Morton \200\231s metatarsalgia. Bursitis. Enthesiti s/dactylitis Robert \200\223Jones fracture from an inversion \200\223pronation injury. or intratendinous . Local or diffuse soft tissue in \202 ammation is common and often misd iagnosed as cellulitis. Swelling is usually marked. L5 pain is referred to the top (dorsum) and S1 pain to the sole of the foot. In older adults OA of midfoot joints is common. Mild synovitis can occur with it and may be caused by CPPD crystals (see Chapter 7). Establish possible causes of forefoot pain \200 In those with forefoot pain, typically re ferred to as metatarsalgia, establish whether the condition is focal or due to arthropathy. Pain under the ball of the foot while walking is nonspeci \201 c but might suggest any MTP joint abnormality, distal metatarsal stress fracture, Freiberg \200\231s disease, plantar nerve neuroma, or bursitis. Patients with RA often describe pain under the MTP joints and a feeling of \200\234walking on pebbles \200\235 (due to joint swelling and/or subluxation). Synovitis of the MTPs is a very common feature of early RA. Acute pain under the forefoot spreading into one or more (adjacent) toes and worse on walking suggests a plantar nerve neuroma (Morton \200\231s metatarsalgia) or intermetatarsal bursitis. Pain associated with paresthesias or numbness under the forefoot might be due to S1 root ir ritation (common) or entrapment of the tibial nerve in the hindfoot (rare). Ask about back pain and other hindfoot problems. Nontraumatic toe pain associated with swelling of the entire toe suggests a dactylitis (associated with SpA). Although many toes may be affected, the dactyl itis may be unilateral and affect just one toe. CHAPTER 2 Regional musculoskeletal conditions 124 The development of hallux valgus is associated with tight footwear. The established deformi ty is associated with altered weight bearing and a second toe (hammer) deformity. Big toe p ain might be due to hallux rigidus. It is usually due to OA and important to recognize as i t may prevent toe dorsi \202 exion suf \201 ciently to lead to a compromised gait pattern . Pain speci \201 cally under the hallux may be due to damage of the sesamoids in the \202 exor hallucis brevis tendon and be misdiagnosed as a joint problem. Ask for a description of the pain \200 As in the hand, neurogenic pain is common and typi cal. \200 Severe or unremitting pain when at rest suggests intrinsic bone pathology. Consider osteonecrosis, infection, fracture, and tumors, e.g., osteoid osteoma. Neurogenic pain may be sharp and well de \201 ned (e.g., in acute L5 or S1 root pain), dee p, achy, and less well de \201 ned (e.g., chronic nerve root symptoms as in spinal or fora minal stenosis) or burning in quality. Paresthesias and numbness may accompany both. If swelling accompanies neurogenic pain, consider a complex regional pain syndrome. There a re numerous triggers, e.g., trauma, surgery. Patients may be unwilling to walk and apparent disability may appear profound. Weakness If true weakness is the major problem rather than pain, the diagnosis is usually b etween a spinal and peripheral nerve lesion (see following sec- tion, Examination). Examination Observation Observe the lower legs and feet from front and back while the patie nt is standing. Note any swelling, deformities, or rashes: \200 Lower-leg deformities to note: tibia varum (or bow legs) in an older adult may be due to Paget \200\231s disease of the tibia. Muscle wasting might suggest disuse atrophy, old polio, or spinal stenosis (bila teral and subtle usually in older adults). Edema or soft tissue swelling may be relevant to an underlying condition, e.g., RA. Although it may cause discomfort, edema from cardiac failure, venous c ongestion, hypoproteinemia, or lymphedema is not painful unless there are ulcers or thrombo phlebitis. Gout can cause swelling anywhere; gouty tenosynovitis can mimic the appearance of a cellulitis in the region of a joint. Calf swelling may be due to vein thrombosis or ruptured popliteal cyst. \200 Common patte rns of foot deformity are: \202 at feet (pes planus) \200 high-arched feet (pes cavus) with high medial arch \200 hallux valgus and rigidus \200 overriding, hammer, and claw toes. Skin conditions from venous abnormalities are common in the elderly. Other skin lesions whi ch may be relevant include purpura, panniculitis \200\224 which is often subtle and over th e shins \200\224and pyoderma gangrenosum. LOWER LEG AND FOOT DISORDERS (ADULTS) 125 Ask the patient to walk in bare feet Gait patterns should be noted: \200 An antalgic ( \200\234limp and wince \200\235) gait is a nonspeci \201 c indicator of pain. \200 A wid e-based gait (>10 cm wider than normal) suggests instability: joint instability, muscle wea kness, or neurologic lesions may be the cause. A foot that slaps down or a high stepping gait suggests tibialis anterior weakness (L4 nerve root or common peroneal nerve lesion). Signi \201 cant weakness of gluteus medius and gluteus maximus in L5 and S1 root lesions r espectively can result in lurching during gait. In the former, as weight is taken on the af fected side, gluteus medius may be weak in controlling the small 2 \200\2233 cm lateral dis placement in the weight-bearing hip that normally occurs. This can be compensated for if th e body center of gravity is brought over the hip by lurching the upper body over the affect ed side. With gluteus maximus lesions (S1) extension of the hip, which helps mediate motion through the stance phase prior to toeing-off, may be weak. Thrusting the thorax forward wi th an arched back (forward lurch) compensates for the weakness and helps to maintain hip ex tension. A \202 at-footed gait with little or weak toe-off may suggest an S1 root lesion; however, \200\234 \202 at-foot \200\235 (loss of the medial arch) with associated hind foot evers ion and heel pain (plantar fasciitis) is extremely common. Often the arch weakness corrects when the patient is asked to walk. Examine the lower leg With the patient supine on the couch, examine the lower leg: \200 A fter a ruptured popliteal (Baker \200\231s) cyst, calf tissues are often diffusely tender a nd swollen. Calf circumferences can be compared (e.g., 10 cm below tibial tubercle). There may also be mild skin erythema. Findings are not speci \201 c. Gout and infection (see Cha pters 7 and 17) are the main alternatives if there is marked tenderness. Check for bruising, swelling, and tenderness around the \201 bula head in patients with f oot drop (possible peroneal nerve palsy). Neurologic examination may be done at this point. Localized anterior tibial tenderness is often found in patients with stress fractures or with pseudofractures (osteomalacia \200\224see Chapter 16). Tibial deformity in adults may be associated with diffuse bony tenderness and heat (arteriovenous shunting) in Paget \200\231s disease (see Chapter 16). Examine the ankle and hindfoot At the ankle and hindfoot, examine for joint and tendon syno vitis, palpate speci \201 c structures and test passive hindfoot joint mobility: \200 Sy novitis of hindfoot joints is not always easily detected. With ankle joint synovitis, thick ened tissue may be felt anteriorly in the ankle crease (where there may be a \200\234sprin gy fullness \200\235) or laterally around the malleoli. CHAPTER 2 Regional musculoskeletal conditions 126 Posterior tibial and peroneal tendonitis are associated with soft tissue swelling of the me dial and lateral hindfoot, respectively. Synovial thickening from ankle and talocalcaneal j oints may also be felt here and synovitis of structures may coexist in RA or SpA. Pain from resisted movement of tendons may not be speci \201 c. Pathology of medial hindfoot structures may be associated with tibial nerve entrapment resu lting in sensory symptoms on the sole of the foot. There may be a positive Tinel \200\231s sign. Posterior heel pain may be due to Achilles tendonitis, enthesitis and mechanical damage to the tendon, and retrocalcaneal bursitis. Deep tenderness may suggest an os trigonum lesion. The loss of passive hindfoot movements is not speci \201 c and can be associated with any cause of ankle or subtalar arthritis (20 \200\22330 of dorsi \202 exion and 45 \200 \22355 of plantar \202 exion is average for the ankle and a 10 \200\22320 inversion \200\223eversion range is average for the subtalar joint). Subtalar joint movement can be dif \201 cult to test accurately. The pain of plantar fasciitis may be elicited by \201 rm palpation of the medial underside of the calcaneum. A negative test does not rule out pathology, as often th e history is more sensitive. Full musculoskeletal examination is required to check for feat ures of SpA such as arthritis/ enthesitis elsewhere and sacroiliitis. Examine for midfoot lesions Identifying speci \201 c midfoot lesions is dif \201 cult, th ough bony landmarks and discrete tender areas can be noted: \200 Twisting the midfoot may elicit pain nonspeci \201 cally. Common lesions include gout, OA, and synovitis associated with RA and SpA. Bony tenderness alone without soft tissue swelling does not rule out synovitis of an adjacent joint. The midfoot is a typical site for neuroarthropathy in diabetes. \200 Bony lumps (exostose s) that may have formed at sites of pressure are common in the foot (e.g., medial or dorsal aspect of the \201 rst MTP joint, base or head of the \201 fth metatarsal, distal talus, or over the midfoot). In the elderly bony pain and skin sores may form at these sites. Both gout and infection result in swelling, skin erythema and localized tenderness. Gout of the \201 rst MTP joint occurs at any one time in 70% of patients with the condition. It can occur anywhere in the foot. Examine the forefoot Check for bony or other swelling, digit separation, and examine the so le of the foot. Squeezing the whole forefoot at the line of the MTP joints is a nonspeci \201 c but useful screening test for painful forefoot lesions: \200 Tender swelling of th e whole toe (dactylitis) occurs in SpA (see Chapter 8), sarcoid (see Chapter 18), and HIV infection (see Chapter 17). Swelling is soft not bony. Tender bony swelling suggests a bunion and is common on the dorsal aspect of the toes and the \201 rst and \201 fth MTP joints. Forefoot splaying and interdigital separation suggests MTP synovitis or interdigital bursitis. MTP joints may be individually tender (simultaneously palpated wi th thumb below and \201 nger above). LOWER LEG AND FOOT DISORDERS (ADULTS) 127 Tenderness between metatarsal heads is typical in Morton \200\231s metatarsalgia. There may be a sensory de \201 cit in the interdigital cleft. The different ial diagnosis (in adolescents) may be osteochondritis of the second and third metatarsal he ad. Check for hallux rigidus \200\224passive dorsi \202 exion should be at least 50 . Extendi ng the big toe passively can reveal an ability to form a medial longitudinal arch in patien ts with \202 at feet (Jack \200\231s test). Discrete bony tenderness without swelling occurs with stress fractures. Uneven callus distribution under the forefoot may suggest an abnormally focused area of wei ght bearing and an underlying mechanical abnormality. Rashes on the sole of the foot are uncommon but important to consider are: pompholyx, pustu lar psoriasis, and keratoderma blennorrhagica (see Reactive Arthropathy in Chapter 8). Loss of sensation under the forefoot may be due to an S1 root lesion, peripheral neuropathy (e.g., diabetes), mononeuritis (e.g., vasculitis \200\224 see Chapter 14), Sj gren \200 \231s syndrome (see Chapter 11), mixed connective tissue disease), or, rarely, tibial nerve entrapment (examine hindfoot). Neurologic examination Neurologic examination is essential in cases where pain is neurogeni c or there is weakness, numbness, or paresthesias (see Table 2.22). Diagnostic procedures Imaging of the lower leg \200 Suspected tibial abnormalities such a s stress fractures and pseudofractures in osteomalacia and Paget \200\231s disease have characteristic radiologica l appearances. Periosteal changes occur in trauma, psoriatic arthritis (above ankle), hypertrophic pulmonary osteoarthropathy (HPOA), and pachydermal periostitis. In athletes with exercise-related pain, a triple-phase bone scan is part of the work-up for anterior shin pain. In suspected (but radiograph-negative) cases of bony disease such as cortical stress fracture, periostitis, or cortical hyperostosis, a bone scan may be useful to identify subtle pathology. Imaging of the foot Information available on radiographs of the hindfoot includes: \200 I ncreased soft-tissue attenuation around the tendon insertion in cases of Achilles tendonitis or retrocalcaneal bursitis. Erosions or periostitis at the Achilles tendon insertion in enthesitis associated with SpA. Erosions in gout and RA-associated retrocalcaneal bursitis. \200 Axial radiographs of the hindfoot are useful in showing talocalcaneal joint abnormalities, e.g., in RA. If radiographs are normal in patients with posterior heel pain, US can show patterns of ten don and bursal in \202 ammation. MR can further characterize any discrete pattern of tendo n injury. CHAPTER 2 Regional musculoskeletal conditions 128 Table 2.22 Patterns of common abnormal examination \201 ndings in lower lumbar nerve root lesions Nerve root Abnormal \201 nding L4 Weakness of ankle dorsi \202 exion (tibialis anterior) Patient \201 nds walking on their heel dif \201 cult (strong ankle dorsi \202 exion nee ded)* Reduced knee re \202 ex (L3 and L4) L5 Weakness of big toe dorsi \202 exion (extensor hallucis longus) Weakness of foot eversion (peroneal muscles, also S1) Sensory de \201 cit over dorsum of foot Reduced ankle re \202 ex (L5 and S1) S1 Weakness of ankle plantar \202 exion (gastrocnemius and soleus) Patient \201 nds walking on, or repeatedly rising onto, tiptoe dif \201 cult* Sensory de \201 cit over sole of foot Reduced ankle re \202 ex Maneuvers may be affected by pain, making interpretation dif \201 cult. Osteonecrosis of an os trigonum or posterior talar process or tarsal navicular may be ident i \201 ed by radiographs. It is invariably located by bone scan and can be characterized f urther, usually with soft tissue swelling, by MR. A plantar spur does not denote current plantar fasciitis. \200 Plantar heel pain may be d ue to a fracture in a spur. Erosions just above the spur may be seen. The thickness of heel fat pad can be gauged from its X-ray attenuation (thin = risk for plantar fasciitis). A fa t pad >23 mm thick in men and >21.5 mm thick in women is associated with acromegaly. Calcaneal fractures or an osteoid osteoma can be seen in some cases with radiographs alone. Bone scans/CT are more sensitive. \200 Patterns of joint, enthesi s, and tendon in \202 ammation can be documented using MR or bone scan. This is useful information when characterizing an arthrop athy. Bony abnormalities in the mid and forefoot are generally revealed by radiographs alone, tho ugh metatarsal stress fractures may be missed. MR can discriminate a plantar neuroma from i nterdigital bursitis and MTP joint synovitis. The former are probably best initially demons trated by US. Other Diagnostic procedures \200 Neurophysiology is a useful adjunct to clinical examinat ion in diagnosis of lower limb neuropathies, and can help discriminate between peripheral (common peroneal o r sciatic) or nerve root causes of foot drop, and also S1 root or tibial nerve entrapment c auses of paresthesias of the sole of the foot. LOWER LEG AND FOOT DISORDERS (ADULTS) 129 Joint/bursa \202 uid aspiration is mandatory in suspected cases of sepsis and should be s ent for culture (remember to consider gonococcus in young adults and TB in patients from en demic or inner-city areas). Fluid should be sent for polarized microscopy if a crystal-indu ced disease is suspected. Laboratory tests requested should re \202 ect suspicion of speci \201 c infective, in \202 ammatory, metabolic, or malignant pathology. Treatment Lower leg disorders \200 Anterior shin pain should be treated according to caus e. If there is also a problem of foot alignment then orthoses that support both the hind foot and mid arch may be very useful. Patients may volunteer that good walking shoes or sneakers help (as is the case with plantar fasciitis).