Knee (Lesson Notes)

Knee – Classical anatomy The Medial meniscus has a thickened outer and thin inner edge; it attaches centrally to the intercondylar tubercles and medially to the capsule. The Lateral meniscus attaches to the popliteus and is more mobile than the medial meniscus (and therefore less easily torn). The medial collateral ligament is broad, flat, and attached firmly to both the capsule and the medial meniscus. The lateral collateral ligament is a longer cord-like structure attached to the femur and fibula, independent of the capsule. The patella – naturally tends to move laterally – due to the shallower lateral angle of the groove and the lateral pull of the main bulk of quadriceps. This is prevented by the pull of the vastus medialis MSK 1/10 Knee – Clinical anatomy Pain from the knee is predominantly felt anteriorly (a), often with localisation to the compartment involved (e.g. anteriorly in patellofemoral disease and anteromedially and anterolaterally in medial and lateral compartment problems, respectively). Prominent radiation down the tibia normally implies marked subchondral bone collapse or intraosseous hypertension. Referred pain to the front of the knee from hip (c) / nerve roots (b) often differs from pain originating in the knee in being (1) less clearly demarcated, (2) frequently accompanied by pain and aching above the knee, and (3) exacerbated by different factors. Posterior knee pain alone suggests a complication of arthropathy (e.g. popliteal cyst, posterior tibial subluxation) or an S2 root lesion; other local causes include hamstring or gastrocnemius enthesopathy, lymphadenopathy, and popliteal aneurysm. 'Locking' is a sudden, usually transient, painful inability to extend the knee. As a symptom, it is important in suggesting a mechanical derangement, e.g. torn meniscus, 'loose' body, or trapping of a fold of the synovium ('plica' syndrome). 'Giving way' describes a feeling of apprehension and loss of confidence in weight bearing on the knee. It predominantly accompanies problems relating to the quadriceps/patellar mechanism or stability. Weakness of the quadriceps, particularly the vastus medialis, or patellofemoral disease, alters vertical 'tracking' of the patella as it moves on the femur and gives rise to this odd feeling of apprehension. Ligamentous instability also alters the mechanics of the knee during weight bearing, so that the patient knows that 'things are not right'. Patellofemoral abnormalities commonly give rise to two characteristic features in the history: Anterior knee pain, which is much worse going up and down (particularly down) stairs or negotiating an incline than walking on the flat. This is because of the maximal stress through that compartment when weight bearing on a flexed knee. Progressive anterior knee pain/aching that develops during prolonged sitting with the knee flexed. The patient typically gets up, stretches the legs, and the aching disappears, only to return after 20min or so of again sitting with knees bent. Swelling Immediate swelling = cruciate ligament = haemarthrosis Over a few hours = meniscal injury (Twisting on bent knee) MSK 2/10 Knee – Examination Inspection Inspection of the Standing Patient Deformity – varus / valgus / flexion / hyperextension Genu varus (bow legs). This commonly reflects isolated medial compartment disease (cartilage loss ? subchondral bone collapse) and is the characteristic deformity of uncomplicated osteoarthritis. Genu valgus (knock knees). This is the usual deformity of arthropathies characterised by synovitis and tricompartmental involvement, leading to cartilage loss throughout the knee. Genu recurvatum. This is particularly characteristic of generalised hypermobility. Posterior tibial subluxation. This produces a stepback deformity and is particularly characteristic of arthropathies that affect the developing knee. Fixed flexion. The knee cannot extend and is always in some degree of flexion. This may complicate a variety of arthropathies, but is particularly common in conditions characterised by synovitis and resolution by fibrosis (e.g. seronegative spondyloarthropathies). Swelling Popliteal cyst / patella alta (high patella) Inspection of the Walking Patient Gait - Look particularly for an antalgic gait, a short step due to fixed flexion, and circumduction of the leg due to fixed extension. Inspection of the Patient Lying on a Couch Skin changes - The anterior (extensor) surface is a common site for psoriasis. Look also for erythema), scars, or other abnormality. Swelling Knee effusion (horseshoe sign) / Bursae/fat pads In front of the patella = prepatellar bursitis. Below the patella, in front of the patellar tendon, = superficial infrapatellar bursitis. Swelling either side of the tendon = deep infrapatellar bursitis or a large infrapatellar fat pad. Large swelling with ill-defined boundaries above or below the medial joint line = prominent medial fat pad (especially in obese women) more subtle swelling below the medial joint line may be seen with anserine bursitis. Muscle Wasting Deformity -Fixed flexion is best assessed while the patient is lying and attempts to straighten the legs. Attitude - may give an idea of pain severity. The patient will keep returning to a flexed-knee position if there is synovitis or a tense effusion causing intra-articular hypertension. Palpation Temperature - Increase in temperature may reflect synovitis (widespread, mainly felt over the whole suprapatellar pouch) or bursitis (localised). If increased warmth is found, be careful this does not relate to varicose veins (often most apparent when standing). Swelling - Fluid within the joint can be detected by one of three signs. Bulge sign (flick fluid from side to side) MSK 3/10 Balloon sign – fingers move lateral on palpation Patella tap – “clonks” onto femur Patellofemoral compartment Press the patella back onto the femur – assess for tenderness & crepitus Active assisted and passive movement (compare active to passive) Knee flexion (requires hip flexion) normally about 115-135° Knee extension Tibiofemoral compartments Tenderness & crepitus Inferior medial collateral ligament enthesopathy - localised tenderness inferior to the medial joint line Anserine bursitis - more diffuse area of tenderness inferior to the medial joint line, often overlapping the site of the inferior medial collateral ligament insertion Superior medial collateral ligament enthesopathy - localised tenderness above the medial joint line Medial fat pad syndrome - wide area of tenderness and 'doughy' swelling superior to, and often overlapping, the medial joint line Inferior lateral collateral ligament enthesopathy - localised tenderness over the fibula head, felt posteriorly on the lateral side Superior collateral ligament enthesopathy - localised tenderness superior to the lateral joint line, centrally on the femur Iliotibial tract ('band') syndrome - line of tenderness that extends from the anterolateral tibia, across the joint line, and up the side of the thigh maximal over the lateral femoral condyle Popliteal tendon enthesopathy - localised tenderness on the lateral femoral condyle in a more anterior position than the superior insertion of the collateral ligament. From running on a cambered, sloped, or uneven track The popliteal fossa Palpated with the knee in mild-to-moderate flexion Swelling - assess communication with the joint by massaging its contents back into the main synovial cavity with the knee in flexion. Tenderness - The medial or lateral hamstring tendons or their insertions, or the medial or lateral insertions of gastrocnemius may be tender to palpation in runners with hamstring or gastrocnemius enthesopathy (particularly following sprinting or running uphill when these muscles are working at full stretch). Such strains are occasionally accompanied by fine crepitus over the tendons. Stability Collateral ligaments – knee 'unlocked' in mild flexion Medial knee pain, particularly at the inferior insertion of the ligament, suggesting collateral ligament enthesopathy (this manoeuvre is basically a stress test for the medial collateral ligament). Cruciate ligaments These are examined with the knee flexed to 90° and the hip to 45° Before testing for excess movement: Palpate the hamstrings to ensure they are relaxed Observe the rounded contour of the knee from the side to ensure the tibia is not starting in a posteriorly subluxed position MSK 4/10 Ankle / Foot – classical anatomy Bones of the foot & ankle 1. Talus (head, trochlear) 2. Calcaneus (body, tuberosity) 3. Cuboid 4. Navicular 5. Cuneiforms 6. Sesamoid 7. Calcaneus (tuberosity, sustenaculum tali) 8. Phalanges 9. Metatarsals 10. Navicular Lateral ankle ligaments (below) 1. Ant & Post tibiofibular ligaments 2. Superior fibular retinaculum 3. Inferior fibular retinaculum 4. Peroneus brevis tendon 5. Bifucate ligament 6. Lateral collateral Medial ankle ligaments (right) 1. Medial collateral ligament 2. Plantar Calcaneonavicular 3. Long plantar ligament 4. Achilles tendon Lateral muscles 1. Peroneus longus – L5-S2 = evertion 2. Peroneus brevis – L5-S2 = evertion Anterior muscles 22 3. Tibialis anterior – L4-5 = Dorsiflexion & inversion 4. Extensor digitorum longus – L5-S1 = Extends proximal phalanges, dorsiflexes foot 5. Extensor hallicus longus – L5S1 = Extends big toe, helps dorsiflexion Deep posterior muscles 6. Flexor digitorum longus – S2-3 7. Tibialis posterior – L4-5 – plantarflex & inverts 8. . Flexor hallucis longus – S2-3 MSK 5/10 6 3 7 8 4 5 Stability is maintained by strong collateral ligaments. The medial deltoid ligament resists eversion of the foot and is very strong (avulsion of the malleolus often occurs before ligament rupture). The lateral ligament is in three bands (the anterior and posterior talofibular ligaments and the calcaneofibular ligament). The anterior talofibular ligament is the first to undergo stress during inversion, and is the most commonly torn. The calcaneofibular ligament may tear, but only after rupture of the anterior talofibular ligament; disruption of both leads to ankle instability. The posterior talofibular ligament is damaged only in severe trauma. The plantar fascia arises from the median prominence of the calcaneus. It is tough and thick proximally, but thins as it extends and divides distally before insertion into the bases of the metatarsal heads MSK 6/10 Ankle / Foot – Clinical anatomy Pain arising from articular or periarticular structures is generally well localised and its site and characteristics alone often suggest the cause. Hindfoot Pain Ankle joint pain is felt anteriorly in a broad line joining the two malleoli, and is worsened by standing or walking. Pain from the subtalar joint is felt mainly posteriorly between the two malleoli, and is particularly aggravated by walking over uneven surfaces when eversion/inversion is required. Localised posterior heel pain and tenderness may result from retro-Achilles bursitis, retrocalcaneal bursitis, or Achilles tendinitis or enthesopathy. With Achilles tendon problems, the pain is often exacerbated by standing on tiptoe (without shoes). Pain beneath the heel, which is worsened by prolonged standing or walking, is usually a result of plantar fascia enthesopathy ('plantar fasciitis'). Midfoot Pain Midtarsal joint disease gives pain in the 'bootlace' area, often most marked during late stance and toe-off phases of walking. Loss of the normal arches ('flat foot') may cause pain in the midsole. Forefoot Pain MTPJ pain is felt below the metatarsal heads (metatarsalgia): it is worsened by standing and walking, and may be described as 'like walking on marbles' if several joints are involved. Burning pain in the sole and toes suggests a neurogenic cause. Morton's neuroma typically causes sharp intermittent pain between the third and fourth digits, particularly when the metatarsal heads are compressed (as with restrictive shoes). Tarsal tunnel syndrome (posterior tibial nerve entrapment) typically causes burning, tingling, and numbness in the distal sole and toes. Referred Pain Pain may be referred to the ankle and foot from the spine and, rarely, the hip. Referred pain from nerve-root irritation follows a dermatomal distribution may be exacerbated by straining and straight leg raising, and may be accompanied by neurological signs. MSK 7/10 Ankle / Foot - Examination Examination Additional information may be obtained by inspecting the patient's footwear for abnormal moulding and wear patterns of the sole and heel. Inspection of the Standing Patient Swelling Ankle synovitis produces diffuse swelling anteriorly, often filling the small depressions in front of the malleoli. Midtarsal synovitis produces only modest, diffuse puffiness over the dorsum of the midfoot. MTPJ synovitis often causes swelling over the dorsum of the forefoot, obscuring the extensor tendons and causing spreading of the metatarsals and toes. IPJ synovitis and digital flexor tenosynovitis may produce a 'sausage toe'. Extensor tenosynovitis à Linear swelling that crosses the ankle Peroneal or tibialis posterior tenosynovitis produces linear or diffuse puffiness around the lateral or medial malleolus, respectively. Achilles tendinitis - swelling of the tendon itself Retrocaleaneal bursitis - eccentric swelling that fills in either side of the tendon Retro-Achilles bursitis - more prominent, superficial swelling. Deformity Arches. The longitudinal arch may be increased (pes cavus, often a result of neurological disease) or diminished (pes plarius or flat foot). In severe flat foot the displaced talus and navicular cause a prominence in front and just below the medial malleolus. Hallux valgus Hammertoe deformity - hyperextension of the MTPJ, with flexion at the proximal interphalangeal joint, or PIPJ Mallet toe results from flexion deformity at the DIPJ. In cock-up toe flexion of both IPJs follows extension and often plantar subluxation at the MTPJ (usually due to polyarthritis). Calcaneovalgus (eversion) usually reflects damage to both the subtalar and ankle joint Calcaneovarus (inversion) Fixed plantar flexion (talipes equinus) usually results from spastic paresis. Congenital clubfoot (talipes) may associate with plantar flexion of the ankle (talipes equinus) or dorsiflexion (talipes calcaucus). Skin and nail changes Loss of hair, ulceration, psoriatic plaques Nails for pitting and dystrophy (psoriasis, chronic Reiter's syndrome), vasculitic lesions, and clubbing. Inspection of the Walking Patient Gait If ankle movement is reduced, the leg may be externally rotated and slightly abducted, giving a 'toe-out' gait, If the heel is painful, heel strike is avoided, the step being shortened and the forefoot striking first. Achilles tendon problems, push off is guarded or avoided, the step again being shortened. Examination of the Recumbent Patient Callosities and inflammed adventitious bursae are particularly common under subluxed MTPJs. They appear to merge into the surrounding MSK 8/10 skin and may be tender to direct pressure. Complications that may be present (particularly in rheumatoid disease) include vasculitic lesions, broken skin with discharge, and secondary infection. Verrucae are tender to direct and, particularly, laterally applied pressure, and show clear demarcation from surrounding skin. Pustular psoriatic lesions and keratoderma blennorrhagica appear identical and plantar erythema is occasionally observed, as on the palms. tinea pedis (athlete's foot) - common in patients with toe deformities Palpation Increased warmth Joint Tenderness, Swelling, and Movement Joint-line tenderness. Soft-tissue swelling arising from the joint. Restriction of passive movement. Pain (especially stress pattern) during movement. Crepitus Metatarsal squeeze Anterior stability Lateral stability MSK 9/10 MSK 10/10