Musculoskeletal investigations - Examination of the hip and knee

Pain in the knee or hip may be referred from one joint to another, so both should be examined, explain Mr Steve Lipscombe and Dr Dan Bunstone.

Inspect the knee for swelling caused by joint effusion due to osteoarthritis or meniscal tear (Photograph: SPL)
Inspect the knee for swelling caused by joint effusion due to osteoarthritis or meniscal tear (Photograph: SPL)

Examination of the hip necessitates examination of the knee and vice versa. Pain may be referred into the thigh or the other joint, so both joints need to be examined.

Rotation of the thigh with the leg extended is a quick method of localising a hip problem. Symptoms in the hip involving the groin may also be confused by pelvic pathology or lumbosacral spine pathology.

Hip pain
Typically, hip pain will be osteoarthritis in the older patient who presents with progressive pain in the groin made worse by mobilisation. Trochanteric bursitis presents with point tenderness overlying the greater trochanter.

Young patients should be considered for Perthes' disease or slipped upper femoral epiphysis. Septic arthritis of the hip occurs in the very young with extreme joint irritability and signs of infection.

Labral tears can occur in young active patients and can be difficult to identify clinically. Avascular necrosis of the femoral head causes progressive pain in the patient on long-term steroids or with alcoholism.

Examination of the hip
Assessment of the gait may localise the pathology to the hip if the adductors are weak, producing a Trendelenburg gait, with the pelvis dropping on the affected side with weight bearing. Leg length discrepancy can occur with advanced degeneration of the hip with shortening, although most people have minor leg length discrepancy.

Thomas' test assesses fixed flexion deformity of the hip, which is otherwise masked by the lumbar lordosis. With the patient lying down, place a hand in the small of the back where the lumbar lordosis is appreciated. Flex the hip and ask the patient to hold the leg in place. The lumbar spine flattens against your hand, obliterating the normal lordosis. Look at the other leg. Any flexion visible in the leg is a fixed deformity.

With the patient lying flat, flex the hip to 90deg and attempt to internally and externally rotate the hip noting any pain.

Abduction is assessed with one hand placed upon the contralateral pelvic crest while abducting the other leg. Once the pelvis begins to tilt as appreciated by the hand placed on the pelvic crest, the position of the leg from the centre line is the range of abduction.

The knee
Swelling and buckling in the knee of a younger patient suggests mechanical derangement within the knee, such as a meniscal tear or ligamentous injury, which may be amenable to surgery. Locking, the inability to achieve full extension due to physical block, can also occur with meniscal tears.

Other common conditions are bursitis and tendinitis around the knee, with pain localised to these areas. Generalised anterior knee pain is common, especially in young women due to patellofemoral dysfunction, with patients complaining of pain made worse when climbing the stairs. Pain worsening with mobilisation in the older patient suggests osteoarthritis.

Examination of the knee
Inspect the knee for swelling, both in the suprapatellar region and the popliteal fossa, caused by joint effusion due to osteoarthritis or meniscal tear.

The alignment of the knee is typically in slight valgus.

As osteoarthritis causes wear mainly in the medial compartment, the alignment in the older patient may be varus (bow legged).

With the patient sat up on the examination couch ask them to fully straighten then bend the knee as much as possible comparing left with right.

The patient should be able to press your hand into the couch on full extension. The distance from the heel to the patient's buttocks can be useful rather than attempting to measure an angle.

Bend the knee to 90deg (you can sit in front of the foot to prevent it slipping). With two fingers assess for tenderness systematically over the tibial tubercle inferiorly, then work up to the patellar tendon, each side of the patella, and the quadriceps tendon.

Feel for palpable gaps or swelling (tendon rupture or tendinitis). Next feel the medial then lateral joint line remembering that each curves posteriorly. Tenderness here should be differentiated from injury to the collateral ligaments.

Joint line tenderness with a history of mechanical symptoms is probably the most reliable sign for meniscal tear. McMurray's test involves flexing the knee to maximum, twisting the foot outwards, and straightening the leg while palpating the medial joint line for pain or click of a trapped meniscal tear.

Knee ligaments
Assessing the knee ligaments can be tricky, especially in a large patient. The collaterals should be tested with the leg fully straight. Grip the thigh then either grip the tibia or cradle it in your arm and apply valgus force (away from the midline to test the medial collateral) then varus (towards, testing the lateral collateral).

There should be little movement with the leg fully straight and only slight movement with no pain with the knee bent at 20deg when the test is repeated.

The cruciate ligaments are difficult to assess. Anterior drawer is easy but unreliable, with the knee bent at 60deg and a firm forward pull on the tibia, again there should be some movement but a firm endpoint.

Lachman's test is more difficult but more reliable and involves attempting the same but with the knee bent to 30deg, gripping both the thigh and tibia.

Assess the extensor mechanism (quadriceps-patella-patella tendon) by holding the knee flexed at 30deg (eliminates any false movement generated by the iliotibial band) then asking the patient to straighten the knee. Feel the tendons in continuity when performing the test.

Conclusion
Hip and knee examination is complex as presenting symptoms often overlap. A systematic examination will usually help to differentiate possible causes of pain and lead to a likely diagnosis.

  • Mr Lipscombe is an orthopaedic registrar in Merseyside, and Dr Bunstone is a GP principal in Cheshire

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