Patient with anterior and lateral hip pain in the setting of longstanding knee complaints and known knee osteoarthritis. Pain is approximately VAS 4/10 during light activity, increasing to VAS 7/10 with prolonged movement. The patient reports episodes of marked functional limitation and a blocking sensation during walking.
Hip
Ultrasound demonstrates degenerative changes of the hip joint compatible with coxarthrosis. There is a mild synovial reaction, consistent with grade 1 synovitis.
Knee
Degenerative changes are present within the medial femorotibial compartment, compatible with grade 2 osteoarthritis, with osteophyte formation at both the femoral and tibial margins.
The medial meniscus is extruded beyond the joint margin and demonstrates findings consistent with a meniscal tear in the setting of degenerative joint disease.
The medial collateral ligament is thickened.
There is fluid distension of the bursa between the semimembranosus tendon and the medial head of the gastrocnemius, consistent with a Baker cyst.
1. Final diagnosis
Sonographic findings of hip osteoarthritis with mild grade 1 synovitis. Medial-compartment knee osteoarthritis, grade 2, with femoral and tibial osteophyte formation. Associated medial meniscal extrusion and degenerative meniscal tear, thickening of the medial collateral ligament, and a Baker cyst.
2. Differential diagnosis
The anterior hip pain may be related to the demonstrated hip osteoarthritis. The differential diagnosis for the lateral hip pain is broader and may include referred pain from the hip joint, lumbar or radicular pathology, or compensatory overload associated with an altered gait pattern. The structural knee abnormalities provide a plausible explanation for the longstanding knee symptoms and may contribute to altered lower-limb biomechanics, although a direct causal relationship with the hip or lower-back symptoms cannot be established by ultrasound.
3. Teaching points
Medial-compartment knee osteoarthritis is frequently associated with osteophyte formation, medial meniscal extrusion, and degenerative meniscal tearing. Meniscal extrusion may reflect loss of normal meniscal function and can accompany progressive compartmental degeneration. Baker cysts commonly develop secondary to intra-articular knee pathology and generally reflect communication with the knee joint rather than an isolated primary abnormality. In patients with coexisting hip and knee degeneration, clinical correlation and radiographs are useful to determine which joint contributes most to pain and functional limitation.
4. Injury/disease information
Weight-bearing radiographs of the hip and knee can further characterise the distribution and radiographic severity of osteoarthritis and help guide management. Conservative treatment generally focuses on maintaining mobility, lower-limb strength, walking function, and overall physical capacity. When pain substantially limits rehabilitation or daily activity, intra-articular knee corticosteroid injection may be considered for short-term symptom reduction. A minimally symptomatic Baker cyst usually does not require separate treatment, as management is primarily directed at the underlying intra-articular knee disorder.
A degenerative meniscal tear in an osteoarthritic knee is not, by itself, an indication for arthroscopic surgery. Treatment decisions are primarily based on pain, functional limitation, clinical findings, and the overall severity of osteoarthritis. Persistent major disability despite appropriate conservative treatment may warrant orthopaedic assessment. Earlier assessment is appropriate if there is true mechanical locking, with a physical inability to complete knee flexion or extension.
If, after assessment of both the knee and hip, the contribution of the hip joint to the symptoms remains uncertain, an image-guided diagnostic intra-articular hip injection with local anaesthetic, with or without corticosteroid, may help further localise the pain source.
Marc is founder of, and trainer at, SonoSkills. SonoSkills is an organization dedicated to MSK ultrasound education. He's also an MSK Sonographer at EchoConsult in Roermond, the Netherlands.
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