Degenerative Joint Disease

Degenerative joint disease, better known as osteoarthritis, is the gradual loss of the articular cartilage that lines a joint, most often the knee, hip or shoulder. It is diagnosed with a handful of clinical tests and a plain X-ray, and it is managed in stages: risk-factor control, braces and medicines first, then joint-preserving surgery, and joint replacement once the whole joint has worn out.

That staged approach was the backbone of the masterclass given on 27 April 2025 by Dr. Ishwar Bohra, Senior Director - Joint Replacement Programme, BLK-Max Super Speciality Hospital, New Delhi, India, to international doctors, with live French translation for colleagues from the Democratic Republic of the Congo. He heads the hospital's joint replacement department, and his own practice centres on the knee, hip and shoulder. One message ran through the whole session: a patient who is identified and referred on time has more options, and needs less surgery, than one who arrives with a neglected joint.

This guide covers the burden of the disease, its definition, its risk factors, and how to diagnose and stage it in an ordinary clinic. Two companion articles go deeper into treatment: partial knee replacement, high tibial osteotomy and the non-surgical options that come before them, and total, robotic and revision joint replacement for stage 4 osteoarthritis. The questions doctors raised at the end of the session, on vitamin D, juvenile arthritis, old fractures and cost, are on the Live Discussion page.

How common is degenerative joint disease?

Degenerative joint disease is the dominant form of arthritis: in Dr. Bohra's figures, about 80% of all arthritis is osteoarthritis, the age-related or early age-related loss of cartilage seen most often in the knee, hip and shoulder. The World Health Organization estimates that about 1.71 billion people worldwide live with a musculoskeletal condition, roughly one person in five.

He drew a historical comparison: before the modern technological era, communicable diseases such as tuberculosis and leprosy were rampant; today the conditions that dominate are diabetes, hypertension and joint disease.

The costs run in two directions. The direct cost is the patient's suffering and the demand placed on medical services that must find solutions for degenerative joint disease. The indirect cost is economic: sick days, lost productivity at work and, across a population, a lower national GDP.

What is degenerative joint disease?

Degenerative joint disease is the gradual loss of articular cartilage, the smooth, low-friction tissue that covers the ends of the bones where they meet, so that one surface glides on the other. Dr. Bohra described where it happens in the three joints he treats most:

• Knee: the cartilage of all three compartments can be affected, the medial and lateral sides of the joint and the patellofemoral compartment behind the kneecap.
• Hip: the socket (acetabulum) and the femoral head that sits in it.
• Shoulder: the shallow socket of the shoulder blade (glenoid) and the humeral head.

He used the definition given by the American Academy of Orthopaedic Surgeons: damage caused by a complex interplay of joint integrity, biochemical processes, genetics and mechanical forces. The point of that definition is that cartilage rarely fails for a single reason. The shape and stability of the joint, the biology of the tissue, inherited susceptibility and the loads placed on the joint combine, and the balance between them decides how fast the surface wears.

Risk factors for degenerative joint disease

The main risk factors are age, female sex, obesity, previous injury, metabolic bone disease, high-impact loading and muscle weakness. Dr. Bohra listed them as follows:

• Age.
• Female sex. Women are more prone to degenerative joint disease, which he linked to reproductive function and the hormonal changes that follow the age of 45.
• Obesity, which increases the load on weight-bearing joints.
• Previous knee injuries, and repetitive injuries to the same joint.
• Metabolic bone disease, which can deform the joint and throw it out of alignment.
• High-impact activity and very high-demand occupations, which load the cartilage repeatedly.
• Muscle weakness. Strong muscles keep the joint surfaces balanced and protected; when they weaken, that protection is lost and the cartilage wears towards arthritis.

He divided these into factors that can be modified and factors that cannot. Age and sex are fixed. Weight, exercise and support for the joint are within the patient's control, and these are where prevention starts.

Malalignment after an old fracture

Alignment came up repeatedly in the session. A fracture of the leg that heals in the wrong position (a malunited fracture) changes the axis along which body weight passes through the knee or hip, and the overloaded side of the joint degenerates. Two of the cases Dr. Bohra presented began this way, one at the knee and one at the hip. Asked whether a tibial fracture left untreated for more than ten years carries any risk of malignant transformation, he was clear: a malunited fracture carries no such risk. Its consequence is mechanical, not oncological.

Vitamin D deficiency

Asked whether vitamin D deficiency is linked to osteoarthritis, Dr. Bohra stressed its importance for the bone. Vitamin D regulates the metabolism of calcium, magnesium and phosphorus, the key minerals of bone strength. When vitamin D is low, bone, including the subchondral bone, the layer of bone directly beneath the cartilage that gives the cartilage its support, can soften. Observational studies have linked low vitamin D to osteoarthritis, but randomised trials have not shown that vitamin D supplements slow cartilage loss or relieve knee osteoarthritis. Deficiency is often missed clinically, and his advice was direct: once hypovitaminosis D is diagnosed, correct it to protect bone health.

How to diagnose degenerative joint disease in clinic

Degenerative joint disease is diagnosed with a clinical examination and a plain X-ray; most of the diagnosis can be made in an ordinary consulting room. Dr. Bohra's examination looks for the site and cause of pain, the patient's muscle power and any grinding in the joint, and then uses a few simple tests:

• Varus and valgus stress tests, which assess the collateral ligaments on the inner and outer sides of the knee.
• The Lachman test, for the anterior cruciate ligament, with tests of the posterior cruciate ligament alongside it.
• Tests for the menisci, the two cartilage cushions inside the knee.
• The duck-walk test, in which the patient walks in a deep squat, to judge the stability of the knee, hip and ankle together.

None of these needs equipment. Their value is in separating a degenerative knee from a ligament or meniscal injury, which needs different management, and in showing how much muscle support the joint still has.

Osteoarthritis stages on X-ray: the Kellgren-Lawrence grades

Osteoarthritis is staged on a plain X-ray from grade 0 to grade 4, and the X-ray also confirms the diagnosis. Dr. Bohra called it a very simple investigation from which osteoarthritis can easily be diagnosed, and he stages the disease with the Kellgren-Lawrence system:

As the grade rises, so does the pain. Dr. Bohra described the progression from initial pain through more pain to severe pain at the final stage.

For practical decisions in the outpatient clinic, he reduces the X-ray to three categories:

1. A normal or near-normal joint: no intervention.
2. A middle-stage joint: rehabilitation can continue, and some patients are candidates for joint-preserving surgery.
3. A severely worn joint: there is no longer any place for medical management. The patient needs surgery.

Degenerative joint disease treatment by stage

Treatment follows the stage: conservative care for early disease, joint-preserving surgery for arthritis confined to one compartment, and joint replacement for stage 4 or failed joints. The rest of Dr. Bohra's lecture followed the X-ray categories up this ladder.

The first two rungs are covered in the article on partial knee replacement and high tibial osteotomy. The last two, including his cases of hip, shoulder and elbow replacement and the cost of a total knee replacement in his practice, are covered in the article on stage 4 osteoarthritis and its surgery.

When to refer degenerative joint disease

Four practical points emerged from the session for doctors who see these patients first.

Stage the joint before choosing the treatment. A plain X-ray, read against the Kellgren-Lawrence grades, decides whether the patient needs rehabilitation, joint-preserving surgery or replacement. Nutraceuticals and injections belong to the early stages; for a severely worn joint, in Dr. Bohra's view, medical management has no remaining role.

Look for the patient with one worn compartment. Dr. Bohra sees more and more younger patients with arthritis confined to the medial or lateral side of the knee. Referred on time, they can have a much smaller operation and return to work within a week.

Correct what can be corrected. Weight and muscle strength are modifiable and both affect how fast cartilage wears; vitamin D deficiency should be corrected for the sake of bone health.

Send complex cases to centres built for them. Neglected deformities, infected replacements and failed implants can still be salvaged, but they need planning, experience and a theatre culture that drives infection towards zero.

Dr. Bohra gave an earlier masterclass, on advances in joint replacement, in May 2024. That session is a separate event with its own guide to joint replacement. Other joint and arthritis masterclasses are listed on the orthopaedics specialty page.