Statistics from the National Center for Chronic Disease Prevention and Health Promotion reveal that nearly 70 million Americans are affected by arthritis and chronic joint pain.1 There are 315 million office visits per year for musculoskeletal complaints and 10 percent of all outpatient visits in general medicine are related to joint pain.2,3

With these statistics in mind, let us consider the following case vignette that involved an elderly patient with knee pain.

An 82 year-old retired female schoolteacher presents to the primary care office with the chief complaint of right knee pain for the past two months. She states the right knee is worse when she walks and is relieved with rest. However, after sitting for an hour, the patient says her knee is stiff and sore. For the past two years, she says both knees have hurt at night after daytime activity such as gardening.

The patient’s past medical history is significant for myocardial infarction and Class I congestive heart failure, hypertension and osteoporosis. The patient’s medications include hydrochlorothiazide 25 mg and Captopril 25 mg once a day. The patient is married, lives in a row home and does not drink or smoke.

The physical examination reveals a well developed and well nourished elderly female in no apparent distress. Her vital signs include a sitting blood pressure of 142/80, a heart rate of 72 with regular rate and rhythm, and respiration at 16 breaths per minute. She weighs 152 lbs. with clothes. She is 5’5” without shoes.

The physical examination of the right knee reveals warmth to the touch but no erythema, swelling or effusion. There is jointline tenderness and positive crepitus. Her range of motion of the right knee is limited in all planes with active and passive range of motion. She has negative joint laxity or deformity. The patient’s sensory exam is intact. Radiographs of the right knee reveal joint space narrowing and osteophytes.

Which of the following is the most likely diagnosis?
A.Calcium pyrophosphate deposition disease
B. Osteoarthritis
C. Osgood-Schlatter disease
D. Gout
A Closer Look At The Differential Diagnosis

A. Calcium pyrophosphate deposition disease (CPPD, Pseudogout) is not the correct answer. One will often see CPPD among individuals over 60 years old. This condition may be hereditary, associated with aging or can occur with metabolic disorders (e.g. hyperparathyroidism, hemochromatosis, diabetes mellitus, hyperthyroidism and gout). Crystals are shed into the joint space, which leads to phagocytosis and enzyme release by leukocytes.

This condition most commonly affects the knee and other large joints. The physical examination for patients with this condition will reveal an erythematous, swollen, warm and painful joint. Radiographs will reveal calcification of cartilaginous structures and signs of degenerative joint disease. Joint fluid analysis reveals calcium pyrophosphate crystals.

B. Osteoarthritis (OA) is the correct answer. Osteoarthritis, which is also called degenerative joint disease, is the most common form of joint disease and is characterized by progressive deterioration and a loss of articular cartilage accompanied by proliferation of new bone and soft tissue in and around the involved joint.

Risk factors for osteoarthritis include age, female sex, race, genetic factors, joint trauma, repetitive stress, obesity and metabolic/endocrine disorders. The onset of joint pain is insidious. Usually, the pain occurs after exercise or after use of the involved joint. Commonly involved sites of osteoarthritis include the distal interphalangeal, proximal interphalangeal, wrist, hip, knee and cervical/lumbar spine. Hand deformities include Heberden’s nodes and Bouchard’s nodes.

Additionally, on physical examination, one will note crepitance, varus or valgus deformities of the knee, restricted range of motion and possibility a mild synovitis. Radiographs reveal osteophytes, joint space narrowing, subchondral cysts and subchondral bone sclerosis.

C. Osgood-Schlatter disease is not the correct answer. Osgood-Schlatter disease results from repetitive injuries at the bone-tendon junction where the patellar tendon inserts into the secondary ossification center of the tibial tuberosity and occurs unilaterally or bilaterally.

The onset of Osgood-Schlatter disease occurs during early adolescence and coincides with the development of the secondary ossification. There is also a higher incidence of this condition among males. The knee pain is exacerbated by running, jumping and kneeling activities.

The physical examination of the knee reveals tenderness and swelling at the insertion of the patellar tendon into the tibial tubercle, full range of motion and no instability. Radiographs in the acute phase of an initial episode may reveal soft tissue swelling. When patients have chronic conditions, one may see small spicules of heterotrophic ossification on the radiographs that are anterior to the tibial tubersoity.

D. Gout is not the correct answer. Gout is a disorder of metabolism that causes hyperuricemia and leads to monosodium urate crystals in joints. This condition most frequently affects men over 30 years old. Gout may be precipitated by rapid fluctuations in serum urate levels from food and alcohol excess, surgery and diuretics. Hyperuricemia is the hallmark of gout.

The physical examination reveals a sudden onset and these patients frequently describe nocturnal joint pain. The involved joint is swollen and exquisitely tender. While the metatarsophalangeal joint of the great toe is most susceptible, feet, ankles and knees are commonly affected. The distribution of the joint pain is asymmetric but may be polyarticular and accompanied by fever.

In cases of chronic gout, one may find tophi (crystal deposition) in ear helix, olecranon bursa, the ulnar surface of the forearm and the Achilles tendon. Radiographs will reveal “punched-out” periatricular effusions, radiolucent urate tophi, soft tissue tophus and erosion late in the disease. Joint fluid analysis reveals monosodium urate crystals.

Pertinent Treatment Recommendations
The treatment of osteoarthritis begins with an emphasis on weight reduction, activity modification, appropriate use of cane and other supports, and isometric exercise to strengthen muscles around the affected joint.

Pharmacological treatment may include topical capsaicin cream, acetaminophen, salicylates, non-steroidal antinflammatories, intraarticular glucocorticoids, hyaluronin, glucosamine and chondroitin.

When it comes to advanced osteoarthritis in patients who have intractable pain, loss of function and have failed aggressive medical management, one may want to refer them for possible surgical procedures ranging from arthroscopic debridement to joint replacement surgery.

Dr. Auth is a physician assistant and is the Director of the Drexel Hahnemann Physician Assistant Program at Drexel University in Philadelphia.