Advanced orthopaedic services

With this website, you can easily plan your next step as a patient by gaining information about general knee and shoulder problems and know how to prepare for consultation and surgery.

Meet Dr Jonker

Dr. Hannes Jonker

Orthopaedic Surgeon
In addition to his interest in sports medicine, Dr. Hannes Jonker, an orthopaedic surgeon, has years experience in knee and shoulder surgery and treatment. He completed a fellowship under Dr Mark Ferguson at the Centre for Sports Medicine and Orthopaedics in Rosebank, Johannesburg, in 2009. His fellowship included advanced training in Europe and the United States. The emphasis on science and sport in Dr. Jonker's practice ensures that he uses the most advanced techniques to restore function to injured and degenerative shoulders and knees. He uses the latest techniques and tried-and-tested prostheses in total knee and shoulder replacements. He follows a multidisciplinary approach in his treatment plan for patients and include disciplines like specialist physician, physiotherapists, biokineticists and sport medicine doctors in his team. As an Ironman 70.3 finisher, and Cape Epic participant himself, Dr. Jonker makes every effort to ensure patients return to work, sports, and their daily lives as soon as possible.

Special procedures

Practice emphasis

General problems of the knee and shoulder

Conditions of the knee and shoulder

The knee

Common problems of the knee are the result of either a disease or a specific type of injury. There are various diseases and types of injuries that can affect the knee. We only provide a summary of the most common types of diseases and injuries of the knee.

Different types of arthritis could affect the knee of which the most common known include: Osteoarthritis – cartilage wears away gradually which causes changes in the adjacent bone. Joint injury or being overweight could be causes of Osteoarthritis. It is also associated with aging. Rheumatoid arthritis – this is an autoimmune disease generally known to affect younger people. The immune system primarily attacks the membrane (synovium) that lines the joint. This then causes inflammation of the joint which causes the cartilage and bone to be completely damaged. In some instances the muscles, tendons and ligaments are also harmed. Other rheumatic diseases include gout, systemic lupus erythematosus (lupus), psoriatic arthritis and reactive arthritis.

  • Gout is an acute and painful form of arthritis and occurs as the bodily waste product, uric acid, forms crystal residue in the joints.
  • Systemic lupus erythematosus (lupus) is an autoimmune disease known for the destructive inflammation of the knee joint.
  • Psoriatic arthritis refers to inflamed joints that present symptoms of arthritis for patients already inflicted with psoriasis or even in the emerging phase of psoriasis.

Reactive arthritis describes forms of arthritis as the result of infectious agents like bacteria or viruses.

Chondromalacia is the softening of the articular cartilage of the kneecap and mostly occurs in young adults. It could be the result of an injury, overuse, the misalignment of the patella or muscle weakness. Instead of the kneecap gliding smoothly over the lower end of the thigh bone, it rubs against it and roughens the cartilage underneath the kneecap. The damage may range from a slightly abnormal surface of the cartilage to a surface worn away to the bone.

Cruciate ligament injuries are also referred to as sprains. Although it is not always associated with pain, it causes immobility. Generally, a sudden twisting motion causes the anterior cruciate ligament to stretch or torn (or both). This could happen when the feet are planted one way and the knees are turned another. On the contrary, direct impact like a rugby tackle causes injury to the posterior cruciate ligament.  

The menisci can be easily injured through the force of rotating the knee while bearing weight. A partial or total tear may occur when a person quickly twists or rotates the upper leg while the foot stays still (for example turning to hit a tennis ball). A tiny tear cause the meniscus to stay connected to the front and back of the knee. However, a large tear could cause the meniscus to be hanging by a thread of cartilage. The seriousness of a tear depends on its location and extent.

The medial collateral ligament is more easily injured than the lateral-collateral ligament. The cause of collateral ligament injuries is typically from a blow to the outer side of the knee that stretches and tears the ligament on the inner side of the knee. Such blows occur in contact sports such as rugby or hockey.

Knee tendon injuries ranges from tendinitis (inflammation of a tendon) to a ruptured (torn) tendon. If a person overuses a tendon during certain activities such as cycling or running, the tendon stretches and becomes inflamed. After repeated stress, the tendon may tear.

The shoulder

The shoulder is the most mobile joint in the human body.  Since the shoulder can easily become unhinged, many problems occur at this joint and cause pain. Swelling, damage or bone changes around the rotator cuff can cause severe shoulder pain. We discuss only some of the most common problems of the shoulder. Others also include but are not limited to these: bone spurs in the shoulder area; bursitis i.e. inflammation of a fluid-filled sac (bursa) that normally protects the joint and helps it move smoothly; dislocation of the shoulder; shoulder separation; frozen shoulder, which occurs when the muscles, tendons and ligaments inside the shoulder become stiff, making movement difficult and painful; overuse or injury of tendons close to the shoulder such as the bicep muscles of the arms; and tears of the rotator cuff tendons.

The rotator cuff is a group of four muscles that surround the humeral-glenoid joint. Their function is to provide stability for the shoulder joint. A rotator cuff muscle can be torn due to years of overusing the shoulder, a traumatic fall or accident or due to the natural muscle breakdown that occurs as we age.

There are many different types of arthritis. The most common is osteoarthritis, which is a degenerative joint disease. The cartilage that covers the ends of the bones in the joint deteriorates and becomes thin. Eventually it wears out, causing the bones in the shoulder joint to rub together. This results in pain and the loss of movement in the joint. Another type of arthritis is rheumatoid arthritis which is an autoimmune disease. The joint lining becomes inflamed as part of the body’s immune system activity. Rheumatoid arthritis is one of the most serious and disabling types, affecting mostly women.

Fractures of the humerus are very common and usually occur at the top of the arm bone. During surgery to repair the break, the fractured pieces are put back together and held in position with pins, wires, sutures or plates. In some instances a shoulder replacement is the best option to repair the fracture and restore function.

As the shoulder has tremendous arc of motion, it is inclined to “dislocation.” When a dislocation occurs, the humerus, or “ball” of the shoulder, comes out of the socket. Most often this occurs in the front of the shoulder. Shoulder dislocation is generally the result of a fall or other trauma. If a person has had a shoulder dislocation, his/her risk to have more dislocations increases.

Armand Duplantis world and Olympic pole vault champion

Our Practice

We raise the bar in orthopaedic care

At Dr. Jonker’s Practice, we strive to make your entire encounter, from walk-in for consultation to the six-week follow-up after surgery, an effective experience. We carefully guide you through the whole process.

Our Mission

Dr. Jonker takes a holistic, multidisciplinary approach to treating both acute and chronic injuries and conditions affecting the shoulder and knee. He integrates the latest musculoskeletal research, innovation and technology into his practice to constantly elevate his level of care. He aims to reducing patient discomfort, increasing mobility and reducing recovery times with personalized rehabilitation plans.

Our Personnel

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Dr Hannes Jonker, orthopaedic surgeon

In Potchefstroom, North West, Dr. Jonker is one of the most respected orthopaedic surgeons focusing on shoulder and knee treatment and surgery. Among the techniques he uses to speed up recovery are minimally invasive arthroscopic surgery, patient-specific instrumentation and kinematic alignment technique in total knee replacement.


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